Edexcel triple biology specification and notes PAPER 1

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have enabled us to see cell structures and organelles with more clarity and detail than in the past and increased our understanding of the role of subcellular structures میں - It has two lenses OCIADOMO Middle -Extremely small structures such as cells cannot be seen without microscopes, which enlarge the image. -The first cells of a cork were observed by Robert Hooke in 1665 using a light microscope. -Lail Magnification of a light microscope: magnification of the eyepiece lens x magnification of the objective lens Size of an object: size of image/magnification = size of object Demonstrate an understanding of the relationship between quantitative units in relation to cells, including: a milli (10) c nano (10) e- calculations with numbers written in standard form b micro (10) d pico (10) لمره اسمه - сувервант all мененале -It is usually illuminated from underneath. -They have, approximately, a maximu magnification of 2000x and a resolving power (this affects olution: 200mm The lower the RP, the more detail is seen. -Used to view tissues, cells and large sub-cellular structures -In the 1930s the electron microscope was developed, enabling scientists to view deep inside sub-cellular structures, such as mitochondria, ribosomes, chloroplasts and plasmids. -Electrons, as opposed to light, are used to form an image because the electrons have much smaller wavelength than that of light waves -There are two types: a scanning electron microscope that create 3D images (at a slightly lower magnification) and a transmission electron microscope which creates 2D images detailing organelles -They have a magnification of up to 2,000,000x and resolving power of 10 nm (SEM) and 0.2nm (TEM) -The discovery of the electron microscope has allowed us to view many organelles more clearly - especially very small structures such as ribosomes (see image). Transmission electron microscopes (TEMS) in particular, have been used to discover viruses such as poliovirus, smallpox and Ebola - and are still used for this function today. This is useful as viruses are much smaller than bacteria, and are very hard to identify using a standard light microscope. Demonstrate an understanding of number, size and scale, including the use of estimations and explain when they should be used Common calculations in microscopy: ability to distinguish between two points) of Core Practical: Investigate biological specimens using microscopes, including magnification calculations and labelled scientific drawings from observations Steps for observing plant and animal cells: 1- Place the specimen on the stage 2- Switch on the microscope so that the light passes through the specimen 3- Make sure the x4 objective lens is clicked into place above the specimen 4- Bring the specimen into focus by looking down the eyepiece lens and moving the coarse focus 5- When the specimen is in focus, move the objective lenses so that the x10 objective lens is clicked into place above the specimen 6- If the specimen is out of focus, bring it into focus using small movements of the fine focus. 7- Repeat steps 5 and 6 with the x40 objective lens Explain the mechanism of enzyme action including the active site and enzyme specificity enzyme a prot that acts as a biological catalyst. -Enzymes are present in many chemical reactions, allowing them to be controlled. -They can both break up large molecules and join together small ones -They are protein molecules and the shape of the enzyme is vital to its function ه من stops. Substrate enzyme -Each enzyme has its own uniquely shaped active site in which the substrate binds -The shape of the substrate is complementary to the shape of the active site, so when they bond Explain how enzymes can be denatured due to changes in the shape of the active site -The optimum temperature in humans is a range around 37 degrees Celsius (body temperature). This temperature is different in other organisms. -The rate of reaction increases with an increase in temperature up to this optimum, but above this temperature it rapidly decreases and eventually the reaction optimoin enzyme- substrate complex forms an enzyme-substrate complex. -When the temperature becomes too hot, the bonds that hold the enzyme together will begin to break. -This changes the shape of the active site, so the substrate can no longer 'fit into' the enzyme. -The enzyme is said to be denatured and can no longer work temperature -The optimum pH for most enzymes is 7 (neutral), but some that are produced in acidic conditions, such as the stomach, have the pH too high or too low, forces that hold amino acid chains that make up the protein will be affected. -This will change the shape of the active site, so the substrate can no longer fit in. -The enzyme is again said to be denatured, and can no longer work. Explain the effects of temperature, substrate concentration and pH on enzyme activity As the substrate concentration (concentration of the substance binding to the enzyme) increases, the rate of reaction will increase - up to a point. This is because, as substrate concentration increases, the rate at which enzyme-substrate complexes can be formed increases. This only occurs up to a point, however - this is called the saturation point, and increasing the substrate concentration above this will have no effect on the rate of reaction. The saturation point is different for every enzyme. PH enrythes dinstining lower optimum pH.. проводит عمرا plateus Core Practical: Investigate the effect of pH on enzyme activity In this practical, we are looking at how pH affects the rate of activity of a particular enzyme. The enzyme being used is called amylase - which breaks down carbohydrates such as starch into simple sugars such as maltose. We can use iodine (dark orange colour) to check for the presence of starch in the solution at any time. When starch is present, the iodine solution will turn to a blue-black colour. Amylase has an optimal pH, and we can use this experiment to estimate what it might be. Materials required: amylase solution, starch solution, iodine solution, labelled buffer solutions of different pH. 1. Place single drops of iodine solution on each well of a tray. 2. Label a test tube with the pH to be tested. Place it in a water beaker with 50 ml cold water and place this above a Bunsen Burner for 3 minutes. 3. Place 2cm of amylase solution, 2cm of starch solution and 1cm of the buffer pH solution in a test tube and start a stopwatch. pubgate conc 4. After 10 seconds, use a pipette to place a drop of the solution into one of the wells containing iodine solution. The mixture should turn blue-black to indicate that starch is still present and has not yet been broken down. 5. Repeat Step 4 after another 10 seconds. Continue repeating until the solution remains orange, and record the time taken 6. Repeat Steps 1-5 with a buffer solution of different pH. 7. Record your results on a graph of pH (on the x-axis) and time taken to complete the reaction (on the y-axis). Why do we use a Bunsen Burner and water beaker? We use this equipment to keep the solution at a relatively constant temperature throughout the reaction (temperature is a control variable in this experiment). What results do we expect to see? The optimal pH of amylase will be at whichever pH the reaction completes in the shortest time. This should be somewhere around pH 7.0 Demonstrate an understanding of rate calculations for enzyme activity Rate calculations are very useful in Biology, and are especially important to determine how fast an enzyme is working (the rate of reaction). To perform a rate the formula: calculation, Rate Change / Time Change refers to the change in the substance being measured (in this case, the enzyme) and time refers to the time taken for that change to occur. Proteases are a type of enzyme used to break down proteins. Explain the importance of enzymes as biological catalysts in the synthesis of carbohydrates, proteins and lipids and their breakdown into sugars, amino acids and fatty acids and glycerol -Carbohydrases convert carbohydrates into simple sugars Example: amylase breaks down starch into maltose. It is produced in your salivary glands, pancreas and small intestine (most of the starch you eat is digested here) -Proteases convert proteins into amino acids Example: pepsin, which is produced in the stomach, other forms can be found in the pancreas and small intestine -Lipases convert lipids (fats) into fatty acids and glycerol Produced in the pancreas and small intestine Soluble glucose, amino fatty acids glycerol pass into bloodstream to be carried to all the cells around body They are used to build new carbohydrates, lipids and proteins, with some glucose being used in respiration. Building these new carbohydrates, lipids and proteins requires some different, more complex enzymes to increase the rate of reaction. Core Practical: Investigate the use of chemical reagents to identify starch, reducing sugars, proteins and fats Starch: lodine solution Add iodine solution to the food sample. If starch is present, the colour will change from orange to blue-black Reducing sugars: Benedict's solution. Add 2cm of the sample solution and 2cm^3 of blue benedict's solution to a test tube. Place in a boiling water bath for 5 minutes, or until there is no further change in colour. Presence of reducing sugar is indicated by a colour change to reddish brown Protein: Biuret Test Add 1cm of 40% potassium hydroxide to the food sample, and then add the same amount of 1% copper sulphate. Shake well and observe colour change if protein is present (blue to violet) Lipids (fats and oils): emulsion test Add 2cm ethanol to food sample and shake thoroughly. Add food sample and shake thoroughly. Add 2cm^3 deionised water and shake thoroughly. If lipids are present, this will be indicated by the formation of a white emulsion layer at the top of the sample. orosis Explain how the energy contained in food can be measured using calorimetry Calorimetry is a way to measure the energy taken in and given out during a chemical reaction. We can use this to measure the amount of 'energy' (calories) in food. To do this, we can: acture transport → 1. Take a tube of 50ml cold water. 2. Record the starting temperature of the water. 3. Place the test tube at 45 degrees and hold a burning food sample just beneath it. 4. When the food is burned up, record the final temperature of the water. Energy transferred to water: = mass of water x 4.2 x temp increase 42 is a constant 'that refers to the specific that capauty of water Explain how substances are transported into and out of cells, including by diffusion, osmosis and active transport Diffusion - orm transport (doe: t require energy). It is important to remember that molecules move in every directi the net (or resultant) movement is from an area of high concentration to one of low concentration. eg spraying deoderant Osmosis - osmosis is also a form of passive transport (does not require energy) but it only applies to water. The same rules as diffusion apply - however there is no such thing as concentration of water', so we say that movement is from a dilute solution to a more concentrated solution, across a selectively permeable membrane. Active Transport - active transport is a form of transport that does require energy. This energy comes from ATP, which is the molecule produced in respiration. Active transport is used to move molecules against a concentration gradient (i.e from an area of low concentration to an area of high concentration). eg nutrients into the blood stream Core Practical: Investigate osmosis in potatoes 1.Cut potato into small discs of equal size 2. Blot the potato disks gently with tissue paper to remove excess water. 3. Measure the initial mass of each disk. 4. Place the disks in sucrose solutions of different concentrations diffusion 5. Blot with tissue paper again and record new mass 6. Find difference in mass and calculate percentage change of mass Calculate percentage gain loss mass in osmosis =(change in mass/ start mass) x100 Semi-permeable Sugar I membrane -0₂: ... 0... Water molecule. motion 9 Osmosis energy for active transport % molecule and collide with each Partany perme membrane , but B2- Cells and control Describe mitosis as part of the cell cycle, including the stages interphase, prophase, metaphase, anaphase and telophase and cytokinesis The cell cycle is a series of steps that the cell has to undergo in order to divide. Mitosis is a step in this cycle- the stage when the cell divides. Stage 1 (Interphase): in this stage the cell grows, organelles (such as ribosome and mitochondria) grow and increase in number, the synthesis of proteins occurs, DNA is replicated (forming the characteristic 'X' shape) and energy stores are increased Stage 2 (Mitosis): The chromosomes line up at the equator of the cell and cell fibres pull each chromosome of the 'X' to either side of the cell. Prophase- nuclear membrane starts to break down Metaphase- chromosomes line up at the equator on spindle fibres Anaphase-chromosomes are pulled to opposite ends of the cell on the spindle fibres Telophase- Nuclear membrane starts to form Stage 3 (Cytokinesis): Two identical daughter cells form when the cytoplasm and cell membranes divide Describe the importance of mitosis in growth, repair and asexual reproduction development, sion by mitosis multicellular organisms is important in their growth replacing damaged cells. Mitosis is also asexual reproduction, as this type of reproduction only involves one organism, so to produce offspring it simply replicates its own cells. Mitosis produces 2 daughter cells, each with identical sets of chromosomes to the parent cell. Because the sets of chromosomes in the daughter cell's nucleus are the same as in the parent cell's nucleus, mitosis produces 2 genetically identical diploid daughter cells Describe the division of a cell by mitosis as the production of two daughter cells, each with identical sets of chromosomes in the nucleus to the parent cell, and that this results in the formation of two genetically identical diploid body cells € interphase B prophase metaphase anaphase (XX) telophase vital part of cytokinesis (*) Describe cancer as the result of changes in cells that lead to uncontrolled cell division Describe growth in organisms, including: a cell division and differentiation in animals In animals, growth occurs via cell division and differentiation. Cell division occurs by mitosis as described above, after which cells can differentiate to specialised forms, specially adapted to their function. For example, cells of the muscular system can bring about movement, and cells of the circulatory system are specialised to transport substances. In animals, almost all cells differentiate at an early stage and then lose this ability. Most specialised cells can make more of the same cell by undergoing mitosis (the process that involves a cell dividing to produce identical cells). Others such as red blood cells (which lose their nucleus) cannot divide and are replaced by adult stem cells (which retain their ability to undergo differentiation). In mature animals, cell division mostly only happens to repair or replace damaged cells, as they undergo little growth. b cell division, elongation and differentiation in plants In plants. growth occurs by cell division and differentiation, but also by a unique process called elongation. Plant cells can grow longer in a specific direction by absorbing water into their vacuoles, and this is controlled by substances called auxins. In plants, many types of cells retain the ability to differentiate throughout life. They only differentiate when they reach their final position in the can still re-differentiate when it is to another position. Explain the importance of cell differentiation in the development of specialised cells Demonstrate an understanding of the use of percentiles charts to monitor growth It is often important to measure the growth of an organism - whether for a farmer to check on the progress of their crops, or for doctors to check whether a child is growing at a normal rate. To do so we use percentiles charts, which can tell us the rate at which an organism of interest is growing. The growth of babies can be measured using mass, length or head circumference. A baby born at the 25th percentile for mass is heavier than 75% of babies. A baby born at the 75th percentile for mass is heavier than 25% of babies. Describe the function of embryonic stem cells, stem cells in animals and meristems in plants A stem cell is an undifferentiated cell which can undergo division to produce many more similar cells, of which some will differentiate to have different functions. Types of stem cells 1. Embryonic stem cells Form when an egg and sperm cell fuse to form a zygote They differentiat into any type of cell the body Scientists can clone these cells (though culturing them and direct them to differentiate into almost any cell in the body These could potentially be used to replace insulin-producing cells in those suffering from diabetes, new neural cells for diseases such as Alzheimer's, or nerve cells for those paralysed with spinal cord injuries 2. Adult stem cells. totipotent plin potent If found in bone marrow they can form many types of cells including blood cells 3. Meristems in plants Found in root and shoot tips They can differentiate into any type of plant, and have this ability throughout the life of the plant They can be used to make clones of the plant- this may be necessary if the parent plant has certain desirable features (such as disease resistance), for research or to save a rare plant from extinction. Discuss the potential benefits and risks associated with the use of stem cells in medicine Therapeutic cloning involves an embryo being produced with the same genes as the patient. The embryo produced could then be harvested to obtain the embryonic stem cells. These could be grown into any cells the patient needed, such as new tissues or organs. The advantage is that they would not be rejected as they would have the exact same genetic make-up as the individual Human Brain Anatomy P medidla oblongata cerebral cotter Describe the structures and functions of the brain including the cerebellum, cerebral hemispheres and medulla oblongata The brain, along with the spinal cord, makes up our Central Nervous System, or CNS. The CNS is responsible for controlling consciousness, movements, thoughts, and emotions, among other things. The brain is made up of several important structures, each contributing their own function. Cerebral hemispheres: The most recognisable part of the brain, the two large cerebral hemispheres take up most of the skull and sit on the left and right-hand sides. Together, these two parts are known as the cerebral cortex and perform a huge variety of functions, including consciousness, memory, intelligence as well as visual and sensory processing. Cerebellum: The cerebellum is a large lump-like structure found at the bottom of the brain, on the rear side. It is responsible for controlling fine movements of muscles, so we can move in complex ways. For example, when you catch. ball, your cerebellum (responsible for your coordination) will be highly active. Medulla oblongata: The medulla oblongata, as the name suggests, is a small 'elongated' structure, and is found in the brainstem, at the base of the brain. It is responsible for maintaining basic autonomic ('automatic) bodily functions, such as breathing, digestion, swallowing and sneezing. Explain how the difficulties of accessing brain tissue inside the skull can be overcome by using CT scanning and PET scanning to investigate brain function Doctors often need to look inside the brain to examine brain tissue for injury and disease. Usually, they are not able to cut the skull open and physically examine the brain as this is highly invasive - and often does not provide any clues about brain function. this case, we can Tomography) and PET (Positron Emission Tomograp scans to look inside the brain more easily. CT scans fire X-Ray radiation at the brain from several different angles to generate a 3D image of the brain. This is useful for examining bleeding within the skull, and damage to brain structures. This is usually not recommended for pregnant women and children, as it exposes the patient to higher doses of radiation than a normal X-ray. For PET scans, a radioactive 'tracer' is injected into the blood before the scan. The scan itself is sensitive to the tracer, so areas where the tracer builds up (which will also be areas with greater blood flow) will be highlighted more brightly on the resulting scan. This is useful for identifying cancerous tumours, as these use more blood than normal tissue. Explain some of the limitations in treating damage and disease in the brain and other parts of the nervous system, including spinal injuries and brain tumours Investigating brain function and treating brain damage and disease is difficult because: It is complex and delicate. It is easily damaged Drugs given to treat diseases cannot always reach the brain because of the membranes that surround it It is not fully understood which part of the brain does what. Cancerous tumours can form in the brain as in any other part of the body (recall that changes in cells leading to uncontrolled cell division is what results in a cancerous nour CT These tumours can push against other structures and blood vessels in the brain, restricting their function. Often, tumours can be buried deep in the brain or spinal cord, making them especially difficult to remove. Explain the structure and function of sensory receptors, sensory neurons, relay neurons in the CNS, motor neurons and synapses in the transmission of electrical impulses, including the axon, dendron, myelin sheath and the role of neurotransmitters The nervous system allows us to react to our surroundings, and coordinate actions in response to stimuli. 1. Receptor cells convert a stimulus into an electrical impulse. 2. This electrical impulse travels along cells called sensory neurons to the central nervous system (CNS). 3. Here, the information is processed and the appropriate response is coordinated, resulting in an electrical impulse being sent along motor neurones to effectors. 4. The effectors carry out the response (this may be muscles contracting or glands secreting hormones). Automatic responses which take place before you have time to think are called reflexes. They are important as they prevent the individual from getting hurt. This because the information travels down a pathway called a reflex arc, allowing vital responses to take place quickly. This pathway is different from the usual response to stimuli because the impulse does not pass through the conscious areas of your brain. 1. A stimulus is detected by receptors. 2. Impulses are sent along a sensory neuron. 3. In the CNS the impulse passes to a relay neuron. 4. Impulses are sent along a motor neuron. 5. The impulse reaches an effector resulting in the appropriate response. 6.Examples of reflex arcs are: pupils getting smaller to avoid damage from bright lights, moving your hand from Synapses are the gaps between two neurons. hot surface to prevent damage. When the impulse reaches the end of the first neuron, a chemical called a neurotransmitter is released into the synapse. This neurotransmitter diffuses across the synapse. When the neurotransmitter reaches the second neuron, it triggers the impulse to begin again in the next neuron. Different neurotransmitters have different effects on the frequency and speed of the impulse in the second neuron. Some nerves are myelinated, i.e they are surrounded by a myelin sheath. The advantage of having nerves surrounded by myelin is that it allows the nerve transmission (or action potential) to travel faster. Myelin is produced by cells called Schwann cells ntrow Explain the structure and function of a reflex arc including sensory, relay and motor neurones Explain the structure and function of the eye as a sensory receptor including the role of: a the cornea and lens Retina: Layer of light sensitive cells found at the back of the eye. When light hits this, the cells are stimulated. Impulses are sent to the brain, which interprets the information to create an image. The retina contains rod cells and cone cells, each of which convert light to nerve impulses destined for the brain. Rod cells are more sensitive to light so they are better seeing light, wherea cone cells allow colour vision. Cornea: The see-through layer at the front of the eye. It allows light through and the curved surface bends and focuses light onto the retina. b the iris pupil -schem Iris: Muscles that surround the pupil. They contract or relax to alter the size of the pupil. In bright light, the circular muscles contract and radial muscles relax to make the pupil smaller- avoiding damage to the retina. In dim light, the circular muscles relax and the radial muscles contract to make the pupil larger- so more light can enter to create a better image c rod and cone cells in the retinal retina ophc neve Ciliary muscles and suspensory ligaments: Hold the lens in place. They control its shape and allow us to focus on objects nearer or further away. Lens: Transparent, curved surface on the front of the eye. The lens, like the cornea, reflects light onto the retina. The process of accommodation: To focus on a near object: The ciliary muscles contract The suspensory ligaments loosen The lens is then thicker and more curved- this refracts the light more To focus on a distant object The ciliary muscles relax The suspensory ligaments tighten The lens then becomes thinner - light is refracted less. Describe defects of the eye including cataracts, longsightedness, short-sightedness and colour blindness Explain how cataracts, long-sightedness and short- sightedness can be corrected Some eye defects occur when light cannot focus on the retina. 1. Short sightedness is called myopia. The lens is too curved, so distant objects appear blurry. 2. Long sightedness is called hyperopia. The lens is too flat, so it cannot refract light enough. Other eye defects include cataracts and colour blindness: Cataracts means clouding of the lens of the eye. This can often occur congenitally (from birth) but can also develop over time. It restricts vision and can be treated by replacing the lens of the eye in surgery. Colour blindness the inability to see certain colours. Full colour blindness is rare, whereas specific colour blindness (eg red-green) very common. This usually occurs because people with the condition do not have enough cone cells in their retina. This is usually genetic. There are a number of treatment methods: They can be treated with spectacle lenses - concave lenses to spread out the light to treat myopia and convex lenses to bring the rays together to treat hyperopia Contact lenses - work in the same way as glasses but allow activities such as sport to be carried out, hard or soft contact lenses last for different lengths of time Laser eye surgery - lasers can be used to either reduce the thickness of the cornea (so it refracts light less) to treat myopia or change its curvature (so it refracts light more strongly) to treat hyperopia Replacement lens - Hyperopia can be treated by replacing the lens with an artificial one made of clear plastic (or adding the plastic on top of the natural lens). The risks include damage to retina or cataracts developing. Topic 3-Genetics Explain some of the advantages and disadvantages of asexual reproduction, including the lack of need to find a mate, a rapid reproductive cycle, but no variation in the population 1. Sexual reproduction involves the joining of male and female gametes, each containing genetic information from the mother or father. Sperm and egg cells in animals Pollen and egg cells in flowering plants Gametes are formed by meiosis, as they are identical. A normal cell has 46 chromosomes. There are two sets of chromosomes (i.e. 23 pairs). In each pair, one chromosome is from the father and the second set are from the mother. Each gamete has 23 chromosomes and they fuse in fertilisation. The genetic information from each parent is mixed, producing variation in the offspring. 2. Asexual reproduction involves one parent with no gametes joining. It happens using the process of mitosis, where two identical cells are formed from one cell. There is no mixing of genetic information. It leads to clones, which are genetically identical to each other and the parent. Examples of organisms that reproduce this way are bacteria, some plants and some animals. Explain some of the advantages and disadvantages of sexual reproduction, including variation in the population, but the requirement to find a mate sexual reproduction: advantages: -creates variation in species -some organisms a species can urvive selection pressures -allows for evolution disadvantages: -requires mate to be found -time for fertilisation/pollination means it takes longer -offspring can have features which are less advantageous asexual reproduction: advantages: -no requirement to find a mate. -rapid production cycle -organisms with beneficial features of the parent can be produced disadvantage: -no variation -a selection pressure could affect all of the organisms of a species Explain the role of meiotic cell division, including the production of four daughter cells, each with half the number of chromosomes, and that this results in the formation of genetically different haploid gametes While mitosis is used for the division of ordinary body cells to produce diploid daughter cells, meiosis is used to produce haploid gametes (sperm and egg cells). Gametes only have one copy of each chromosome. Meiosis is the formation of four non-identical cells from one cell. The cell makes copies of its chromosomes, so it has double the amount of genetic information. The cell divides into two cells, each with half the amount of chromosomes (46). The cell divides again producing four cells, each with a quarter the amount of chromosomes (23). These cells are called gametes and they are all genetically different from each other because the chromosomes are shuffled during the process, resulting in random chromosomes ending up in each of the four cells These gametes with 23 chromosomes join at fertilisation to produce a cell with 46 chromosomes, the normal number. This cell divides by mitosis to produce many copies. produced, and embryo The cells begin to take on different roles after this stage (differentiation). More I more. Describe DNA as a polymer made up of: a two strands coiled to form a double helix b strands linked by a series of complementary base pairs joined together by weak hydrogen bonds c nucleotides that consist of a sugar and phosphate group with one of the four different bases attached to the sugar DNA, found in the nucleus, is a chemical that contains genetic material. DNA stands for deoxyribonucleic acid, and this is a polymer that contains instructions for the body. It is made up of many small parts called nucleotides. Each nucleotide is made up of one sugar molecule, one phosphate molecule (which form the backbone) and one of the four types of organic bases. Base pairs U.S. National Library of Medicine Adenine Thymine Guanine Cytosine Sugar phosphate backbone The four types of organic bases are A, C, G, T. Each DNA molecule is made up of two DNA strands which are twisted together. Each base is connected to another base in the other strand. A bases only connect to T bases, and C bases only connect to G bases. This is called complementary base pairing. The order of the different bases forms a genetic code - e.g. A, G, T, T, C, A A etc. DNA is a polymer (long molecule) made up of two strands which are wound around each other to form a structure called a double helix. A gene is a short section of DNA. Each gene codes for many amino acids, which are joined together to make a specific protein. There are 20 types of amino acid. Describe the genome as the entire DNA of an organism and a gene as a section of a DNA molecule that codes for a specific protein The word genome describes all the genetic information (DNA) of a single organism. The human genome has been studied, which has improved our understanding of the genes linked to different types of disease, the treatment of inherited disorders and has helped in tracing human migration patterns from the past. Explain how DNA can be extracted from fruit grind/ squash cells. -add detergent/ salt solution/protease -heat in a water bath to 60°C -add ice cold ethanol -DNA forms as a white precipitate Explain how the order of bases in a section of DNA decides the order of amino acids in the protein and that these fold to produce specifically shaped proteins such as enzymes Each group of three bases (e.g ACT, AGG, GAC) codes for an amino acid. The amino acids are joined together and fold to make a protein. It is the different types and order of amino acids that determine which type of protein it is. Often these proteins are enzymes, which need to have a very specific shape. Therefore it is the order of bases in DNA that determine which proteins are produced. There are also non-coding parts of DNA that do not code for proteins. Some of them are responsible for switching genes on or off, i.e. controlling whether the gene is used to form a protein or not. the stages protein synthesis, including transcription and anslation: DNA contains the genetic code for making a protein, but it cannot move out of the nucleus as it is too big. The mRNA nucleotides themselves are then Joined together, creating a new strand called the mRNA strand. This is a template of the original DNA. a RNA polymerase binds to non-coding DNA located in front of a gene An enzyme called RNA polymerase binds to non-coding DNA located in front of a gene on the DNA strand. b RNA polymerase produces a complementary mRNA strand from the coding DNA of the gene The two strands of DNA pull apart from each other, and RNA polymerase allows mRNA nucleotides (messenger RNA: a different type of nucleotide) to match to their complementary base on the strand. c the attachment of the mRNA to the ribosome The mRNA then moves out of the nucleus to the cytoplasm and onto structures called ribosomes. d the coding by triplets of bases (codons) in the mRNA for specific amino acids At the ribosomes, the bases on the mRNA are read in threes (triplets) to code for an amino acid (the first three bases code for one amino acid, the second three bases code for another etc). The corresponding amino acids are brought to the ribosomes by carrier molecules called tRNAs - transport RNAs. e the transfer of amino acids to the ribosome by tRNA f the linking of amino acids to form polypeptides These amino acids connect together to form a polypeptide (amino acids linked by peptide bonds). When the chain is complete the protein folds to form a unique 3D structure, which is the final protein. Describe how genetic variants in the non-coding DNA of a gene can affect phenotype by influencing the binding of RNA polymerase and altering the quantity of protein produced Genetic variants are small changes in the order of bases that make up a strand of DNA. They can affect the structure of proteins in different ways, depending on whether they occur in coding DNA or non-coding DNA Genotype refers to the genes present in the DNA of an individual, whereas phenotype refers to the visible effects of those genes (e.g the proteins that they code for). 1.DNA contains the genetic code for making a protein, but it cannot move out of the nucleus as it is too big. 2.The mRNA nucleotides themselves are then joined together, creating a new strand called the mRNA strand. This is a template of the original DNA. An enzyme called RNA polymerase binds to non-coding DNA located in front of a gene on the DNA strand. 3. The two strands of DNA pull apart from each other, and RNA polymerase allows mRNA nucleotides (messenger RNA: a different type of nucleotide) to march to their complementarv pase on the strand 4. The mRNA then moves out of the nucleus to the cytoplasm and onto structures called ribosomes. DNA deyse. pamp palex DNA molecule 5. At the ribosomes, the bases on the mRNA are read in threes (triplets) to code for an amino acid (the first three bases code for one amino acid, the second three bases code for another etc. 7. The corresponding amino acids are brought to the ribosomes by carrier molecules called tRNAs - transport RNAs. 8. These amino acids connect together to form a polypeptide (amino acids linked by peptide bonds). 9. When the chain is complete the protein folds to form a unique 3D structure, which is the final protein. mudatuse DNA strand 3 (template) TRANSCRIPTION mRNA TRANSLATION Protein RNA Gene 1 Goo Codon 18MMMMMMA Trp Gene 2 Amino acid Phe Gene 3 Gly Ser Coding DNA: A genetic variant will alter the sequence of bases (e.g ACT -> AGT) and therefore will change the sequence of amino acids (e.g Glycine -> Valine). alters the final structure of the protein produced. Non-Coding DNA: A genetic variant in the coding DNA can affect phenotype differently. The enzyme RNA polymerase (see Section 3.8B) binds to non-coding DNA, and a change in the order of bases in this non-coding DNA can affect the amount of RNA polymerase that can bind to it. If less RNA polymerase is able to bind, less mRNA can be formed and the structure of the final protein is affected. Mutations change the sequences of bases in DNA. Either: 1. A base is inserted into the code •As they are read in threes, this changes the way it is read. • It may change all the amino acids coded for after this insertion. 2. A base is deleted from the code • Like insertions they change the way it is read. • It may change all the amino acids coded for after this deletion. 3. A base is substituted . This will only change one amino acid in the sequence or it may not change the amino acid (as the new sequence can sometimes still code for the same amino acid) Describe how genetic variants in the coding DNA of a gene can affect phenotype by altering the sequence of amino acids and therefore the activity of the protein produced A change in the type/sequence of amino acids will affect the way it folds and therefore the structure. Most mutations do not alter the protein or only do so slightly. Some can have a serious effect and can change the shape The substrate will not fit into the active site so it cannot act as a protein. • A structural protein may lose its shape. There can also be mutations in the non-coding parts of DNA that control whether the genes are expressed. Describe the work of Mendel in discovering the basis of genetics and recognise the difficulties of understanding inheritance before the mechanism was discovered Trained in mathematics and natural history in Vienna • Worked in the monastery gardens and observed the characteristics passed on to the next generation in plants He carried out breeding experiments on pea plants. • He used smooth peas, wrinkled peas, green peas and yellow peas and observed the offspring to which characteristics they inherited Through keeping a record of everything he did and eventually publishing his work in 1866, he came to these conclusions: Offspring have some characteristics that their parents have because they inherit 'hereditary units' from each. One unit is received from each parent. Units can be dominant or recessive, and cannot be mixed together. Mendel was not recognised till after his death as genes and chromosomes were not yet discovered, so people could not understand. • In the late 19th century chromosomes as a part of cell division were observed In the 20th century, it was understood that chromosomes and units had similar behaviours. It was decided that units (now known as genes) were on the chromosomes. • The structure of DNA was determined in 1953, which meant we were able to understand how genes worked. Explain why there are differences in the inherited characteristics as a result of alleles Alleles (different forms of the same gene) lead to differences in inherited characteristics. This is because different alleles code for different forms of the same protein - an allele that codes for a damaged form of a protein can cause illness. For example, in a condition called Huntington's Disease, an allele of the gene that codes for a particular protein is different. This leads to the protein becoming folded incorrectly and causing the condition. Explain the terms: chromosome, gene, allele, dominant, recessive, homozygous, heterozygous, genotype, phenotype, gamete and zygote chromosome: a long, coiled molecule of DNA that carries genetic information in the form of genes allele: a version of a gene dominant: an allele that is always expressed recessive: an allele that is only expressed in the absence of dominant alleles homozygous: 2 of the same alleles. heterozygous: 2 different alleles phenotype: all of an organisms genetic material phenotype: an organisms observable traits due to the interactions of genes and the environment gamete: sex cells with haploid dna. zygote: a diploid cell formed in the fusion of 2 gametes Explain monohybrid inheritance using genetic diagrams, Punnett squares and family pedigrees Family trees show the inheritance of different phenotypes over generations in the same family. A monohybrid (single gene) cross looks at the probability of the offspring of two parents having certain genotypes and phenotypes. This is done using the alleles Punnett square diagram the two parents have for a gene and a Punnett square diagram. You should be able to draw and use mother IX X XX Y XY X XX XY Describe how the sex of offspring is determined at fertilisation, using genetic diagrams Uppercase letters are used to represent dominant characteristics. Lowercase letters represent recessive characteristics. You can choose any letter but usually either A or B is used for simplicity. Notice that combining the alleles shown above results in 4 chance of having an offspring who is homozygous dominant (BB, or has two dominant alleles), and there is no chance of having a homozygous recessive offspring (as both parents have the allele). Whether or not the Bb (heterozygous recessive offspring show symptoms depends on whether the condition itself recessive or dominant. Calculate and analyse outcomes (using probabilities, ratios and percentages) from monohybrid crosses and pedigree analysis for dominant and recessive traits Family pedigrees are used to show how a condition (or more specifically, the allele which causes it) are passed down through different generations. We can use them to better visualise certain patterns - for example, the way that recessive alleles normally 'skip a generation': We usually use squares to represent males, and circles to represent females in the lineage. Black shapes represent an affected individual, and white shapes represent an unaffected individual. A line through the shape means that the individual is deceased. A line passing directly between two shapes means that the two are partners, and a line overhanging a group of individuals means that they are siblings Describe the inheritance of the ABO blood groups with reference to codominance and multiple alleles There are often important patterns to be seen in inheritance of particular genes. For example, sometimes dominant alleles can be expressed together in the same individual. This called codominan Wh three or more present at the same position, or locus. An example of codominance and multiple alleles is the ABO blood group system, where there are alleles for A, B and O that can all be expressed at the same locus (position). Only two of them are expressed at once, however, with the following pattern (note that the O allele i recessive, and the A and B alleles are dominant): Explain how sex-linked genetic disorders are inherited Some alleles are not found on chromosome pairs 1-22: instead, they are found on the sex chromosomes X and Y. Remember that in humans, males carry an X and a Y chromosome (XY), whereas females carry two X chromosomes (XX). If these alleles cause a genetic disorder, it is known as a sex-linked genetic disorder. The majority of sex-linked conditions are found on the X chromosome. State that most phenotypic features are the result of multiple genes rather than single gene inheritance Most phenotypic features are the result of multiple genes acting together, and not single genes. For example, as many as 16 genes are thought to be responsible for human eye colour Variation between individuals is an important factor in allowing natural selection to happen, and it originates from one of two main areas: a) Genetic variation - different characteristics can arise as a result of both random mutation and sexual reproduction. Random mutation occurs in gametes to produce offspring with 'brand new phenotypic characteristics, whereas sexual reproduction causes the offspring to have a new combination of characteristics from both b) Environmental variation - characteristics can also be caused by an organism's environment, but these changes are generally not heritable (there is no change in the DNA of the organism). For example, a child who does not receive adequate nutrition will not grow to their full height, however this has no effect on their potential height as determined by their genetics. Describe the causes of variation that influence phenotype, including: a genetic variation - different characteristics as a result of mutation and sexual reproduction b environmental variation - different characteristics caused by an organism's environment (acquired characteristics) Discuss the outcomes of the Human Genome Project and its potential applications within medicine -improved our understanding of the genes linked to different types of disease - helped in the treatment of inherited disorders - helped in tracing human migration patterns from the past. State that there is usually extensive genetic variation within a population of a species and that these arise through mutations Genetic mutation can have varying effects on the phenotype. For example, the majority of mutations have no effect on the phenotype as they occur in DNA which does not code for proteins (non-coding DNA). its be present same loci not necessarily expres at once), we say that multiple alleles State that most genetic mutations have no effect on the phenotype, some mutations have a small effect on the phenotype and, rarely, a single mutation will significantly affect the phenotype Some mutations can have a small effect on the phenotype, and other mutations, rarely, can significantly affect the phenotype - for example, changing one base can change one amino acid in a protein. If the protein was an enzyme, this has the potential to change the shape of the active site so that substrates can no longer bind to it. Topic 4 - Natural selection and genetic modification Describe the work of Darwin and Wallace in the development of the theory of evolution by natural selection and explain the impact of these ideas on modern biology Alfred Russel Wallace developed the theory of speciation, and therefore evolution by natural selection. On his travels, he had the idea that the individuals who did not have characteristics to help them survive a change in the environment would die out. He published joint studies with Darwin. The publication of 'On the Origin of Species' meant Darwin received the credit for the theory. He continued to work a cross the world to colle evidence - one of his most important works was on warning colouration in animals Much more evidence over time has resulted in our current understanding. The process of speciation: 1. Variation exists within a population as a result of genetic mutations. 2. Alleles which provide a survival advantage are selected for through natural selection. 3. Populations of a species can become isolated, for example through physical barriers such as a rock fall preventing them from breeding together. 4 Different alleles may be advantageous in the new environment, leading to them being selected for. 5. Over time the selection of different alleles will increase the genetic variation between the two populations. 6. When they are no longer able to breed together to produce fertile offspring, a new species has formed. Scientist and naturalist Put forward the theory of evolution . This was supported by experimentation and his knowledge of geology and fossils that he discovered on a round the world expedition • Published 'On the Origin of Species* in 1859 Explain Darwin's theory evoluti by natural selection Theory of Evolution: Variation exists within species as a result of mutations in DNA Organisms with characteristics most suited to the environment are more likely to survive to reproductive age and breed successfully called survival of the fittest. The beneficial characteristics are then passed on to the next generation Over many generations the frequency of alleles for this advantageous characteristic increase within the population There was lots of controversy surrounding his ideas for many reasons: 1. It contradicted the idea that God was the creator of all species on Earth. 2. There was not enough evidence at the time as few studies had been done on how organisms change over time. 3. The mechanism of inheritance and variation were not known at the time. Explain how the emergence of resistant organisms supports Darwin's theory of evolution including antibiotic resistance in bacteria Bacteria are labelled resistant when they are not killed by antibiotics which previously were used as cures against them. • Bacteria reproduce at a fast rate. Mutations during reproduction can result in new genes, such the gene for antibioti sistance. the creation of a new strain. Exposure to antibiotics creates a selection pressure, as those with antibiotic resistant genes survive and those without die. As a result those with antibiotic resistance can reproduce and pass on the advantageous gene to their offspring. Therefore, the presence of these new, resistant bacteria supports Darwin's theory of natural selection (as the new bacteria have been selected by the environment to have a feature (resistance) advantageous to survival) This population of antibiotic resistant bacteria increases. Bacterial diseases spreads rapidly because people are not immune to these new resistant bacteria and there is no treatment for it. An example is MRSA. Called a 'superbug' as it is resistant to many different types of antibiotics Common in hospitals: spreads when doctors and nurses move to different patients Describe the evidence for human evolution, based on fossils, including: Fossil evidence shows how developments in organisms arose slowly. This because we can use carbon dating and related techniques to estimate when a fossil was formed, giving us a more complete picture of how an organism or species developed over time. Examples of these include: a Ardi from 4.4 million years ago Ardi - Ardipithecus ramidus, or Ardi, is the oldest known human ancestor - estimated to have lived 4.4 million years ago. Her fossilised skeleton contains many "humanoid" features but also resembles an ape; thus, it is phenotypically somewhere between the two. The presence of this intermediate organism is good evidence that natural selection, eventually evolution, occurred gradually. The bone struct in ardi's feet giv us a clue- it's different from that of chimpanzees, suggesting that the two evolved separately rather than together b Lucy from 3.2 million years ago Lucy - This fossilised skeleton dates from 3.2 million years ago. Her bone structure suggests that she walked in an upright, human-like position. However, Lucy had a small, chimp-like skull and brain and therefore represents another intermediate between apes and early humans. c Leakey's discovery of fossils from 1.6 million years ago c) Fossils discovered by the archaeologists Louis and Mary Leakey in the 1950s helped support the theory of natural selection, especially an early fossil which contained remnants of stone tools (thought to be an early toolmaker), and Homo habilis, which is now considered to be one of the most important early human species. Describe the evidence for human evolution based on stone tools, including: a the development of stone tools over time Early Stone Age tools - Homo habilis (1.5 million years ago) Used basic pebble tools (Oldowan tools') created by smashing rocks together. These tools had simple uses, such as cracking nuts. Age tools - Hon neanderthalensis (40,000 years ago) and These more advanced species used pointed arrowheads, spears and hooks This enabled more advanced tasks to be carried out, such as catching fish. b how these can be dated from their environment Radiometric carbon dating - by looking at the natural radioactive decay of an isotope of Carbon (Carbon-14) we can estimate how long ago an organism lived. If any once-living material is found with a tool, such as a piece of wood or fur, we can date this to find the age of the rock. 2. Stratifying rock layers - looking at the layer of sediment in which a rock was found is a useful tool for archaeologists. Each layer of sediment, and everything within it, must have been formed at the same time. Therefore, we can date once-living fossils in this layer and use this to estimate when the tools were formed. Describe how the anatomy of the pentadactyl limb provides scientists with evidence for evolution A pentadactyl limb is a limb with five digits. This can be seen in a number of organisms, implying that they all come from a common ancestor - and that each 'branched off at some stage of evolution. This could have been due to different selection pressures within different environments. The human hand has five digits (four fingers and a thumb), but bats, cats, horses and birds also have this pattern within their limbs. However, that does not mean that we evolved directly from these animals but humans are distantly related to them via a common ancestor. Describe how genetic analysis has led to the suggestion of the three domains rather than the five kingdoms classification method It is important to classify organisms so that we know about the genetic relationships between species and organisms. We can do this by the old Five Kingdoms system, or the newer Three Domains system. Five Kingdoms system The Five Kingdoms Classification splits all organisms into one of 5 groups: }}(( Animals Plants lomo sapiens Fungi Prokaryotes (e.g bacteria) Protists (e.g algae, amoebas and other single-celled eukaryotic organisms) Each kingdom is then subdivided into a phylum, class, genus, order and species. These are different for each organism. For example, a human (Homo sapiens) would be of the Animal kingdom, its phylum is Chordata, class is Mammalia and Order is Primate. The binomial naming system is based on the genus and species; for example, Homo sapiens is of the genus Homo, which also contains Homo habilis and Homo erectus, to name a few. Three-domain system Developments in science such as the improvement of the microscope and increased knowledge of biochemistry (for example, RNA sequence analysis) found that some species were more distantly related than first thought Carl Woese added three large groups called domains above kingdoms Archaea: primitive bacteria which live in extreme environments such as hot springs Bacteria: true bacteria (despite having similar features to archaea) Eukaryota: organisms who have a nucleus enclosed in membranes, includes the kingdoms protists, fungi, plants and animals Explain selective breeding and impact food plants and sticated animals Selective breeding is when humans choose which organisms to breed in order to produce offspring with a certain desirable characteristic (e.g animals with more meat, plants with disease resistance or big flowers). This has been happening for many years since animals were domesticated and plants were grown for food Parents with desired characteristics are chosen. They are bred together. • From the offspring those with desired characteristics are bred together. The process is repeated many times until all the offspring have the desired characteristic. The problem is that it can lead to inbreeding. Breeding those with similar desirable characteristics means it is likely you are breeding closely related individuals. This results in the reduction of the gene pool, as the number of different alleles reduce (as they mostly have the same alleles). . This means if the environment changes or there is a new disease, the species could become extinct as they all have the same genetic make-up (so the chance of a few organisms having a survival advantage and not dying is reduced). This is particularly relevant in selective breeding of plants, as one disease could spread rapidly and destroy the entire population of crops. This could cause severe economic problems, especially for the farmers who rely on income from their crops. Another problem small gene pool lead to a greater chance of genetic defect being present in offspring, recessive characte are more likely to present. This is particularly relevant in domesticated animals, which have much higher frequency of genetic conditions than normal. Describe the process of tissue culture and its advantages in medical research and plant breeding programmes Tissue culture is a method of culturing living tissue, i.e making it grow outside the organism, within a growth medium. This s especially useful for plants - we can produce an entire field of identical cloned crops using just a small cutting. Tissue culture can also be used to culture animal and human tissues outside of the body. In plants: 1. Take the plant that you would like to clone - for example, a plant with desirable characteristics. 2. Using tweezers, remove a piece of tissue from a fast-growing region of the plant, e.g the root or shoot tip. 3. Using aseptic technique (maintaining sterile conditions), place the tissue on a special growth medium (containing hormones and nutrients). 4. Once the tissue has developed enough (e.g. produced shoots and roots), it can be transferred to compost for further growth. Describe genetic engineering as a process which involves modifying the genome of an organism to introduce desirable characteristics Genetic engineering: Modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic. • Plant cells have been engineered for disease resistance or to have larger fruits Bacterial cells have been engineered to produce substances useful to humans, such as human insulin to treat diabetes. Describe the main stages of genetic engineering including the use of: a restriction enzymes Genes from chromosomes are 'cut out using restriction enzymes. The same restriction enzymes are used to cut the vector (such as a virus or bacterial plasmid) into which the genes will be placed. b ligase c sticky ends Ligase enzyme is used to attach the sticky ends of the gene and the vector together, to produce a recombinant gene product. d vectors The vector is placed in another organism at an early stage in development so the desired gene moves Into its cells and cause the organism to grow with the desired characteristics. In plants the vector is put into meristematic cells (unspecialised cells) which can then produce identical copies of the modified plant. Explain the advantages and disadvantages of genetic engineering to produce GM organisms including the modification of crop plants, including the introduction of genes for insect resistance from Bacillus thuringiensis into crop plants Genetically modified crops They are engineered to be resistant to insects and to herbicides. This will result in increased yields as less crops will die. Genetic modification in medicine • It may be possible to use genetic engineering to cure inherited disorders. . It is called gene therapy and involves transferring normal genes (not faulty) into patients the correct proteins are produced Bacillus thuringiensis is the name of a bacteria that produces toxins that kill insect larvae. This is a useful function for crops, so we use genes from the bacteria in crops to increase their insect resistance. Genes are cut out from the bacteria using restriction enzymes, and re-inserted into the crop using ligase, as described above. The crop will then produce the toxin- any insects that eat the crop will die. As a result, less of the crop gets eaten by insects, increasing the crop yield and profits. However, there are concerns over this method - we don't know if the toxin has any effect on human health, for example. Killing insects also results in a loss of biodiversity, which can affect the entire ecosystem. Explain the advantages and disadvantages of agricultural solutions to the demands of a growing human population, including use of fertilisers and biological control We can use various agricultural solutions to cope with the demands of a growing human population. Two of the most useful methods are: 1) Fertilisers - fertilisers provide useful nutrients (nitrates and phosphates) plants, making them more resistant to environmental conditions and able to grow faster and larger - resulting in increased crop yields. However, excess fert can often run off into rivers, killing and other dlife affecting biodiversity. 2) Biological control - biological control is the use of certain species to control population of other species. For example, Aphelinus abdominalis, the aphid killer wasp, has been used successfully to control aphid populations - which feed on fruit crops. However, this reduces biodiversity, and again, has a knock-on effect across the whole ecosystem. Evaluate the benefits and risks of genetic engineering and selective breeding in modern agriculture and medicine, including practical and ethical implications Topic 5 - Health, disease and the development of medicines Describe health as a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity, as defined by the World Health Organization (WHO) Describe the difference between communicable and non-communicable diseases Communicable and non-communicable disease Communicable diseases are those which can be transferred between individuals. This might be through air particles from coughing (known as droplet infection), from parasites in faeces (the faecal-oral route) or through bodily fluids including blood, semen and breast milk. These include viral infections such as flu, bacterial infections such as the common cold, and parasitic infections. Non-communicable diseases are those which cannot be transferred between individuals. These are usually conditions with a genetic component or conditions acquired due to lifestyle factors. Some examples are cardiovascular disease, asthma, and diabetes. Explain why the presence of one disease can lead to a higher susceptibility to other diseases Often, the presence of one disease can lead to increased susceptibility to other diseases. For example: Having HIV means that your immune system is impaired, leaving you at risk to many other 'opportunistic infections, caused by bacteria, viruses and fungi. Having a particular virus called HPV can increase a woman's risk of developing cervical cancer. Describe a pathogen as a disease-causing organism, including viruses, bacteria, fungi and protists Viruses Very small Move into cells and use the biochemistry of it make copies of itself This leads to the cell bursting and releasing all of the copies into the bloodstream The damage and the destruction of cells makes the individual feel ill bacteria small they multiply very quickly through dividing by a process called binary fission they produce toxins that can damage cells Fungi They can either be single celled or have a body made of hyphae (thread like structures) They can produce spores which can be spread to other organisms Protists Some are parasitic, meaning they use humans and animals as their hosts (live on and inside, causing damage) Describe some common infections, including: a cholera (bacteria) causes diarrhoea b tuberculosis (bacteria) causes lung damage c Chalara ash dieback (fungi) causes leaf loss and bark lesions d malaria (protists) causes damage to blood and liver e HIV (virus) destroys white blood cells, leading to the onset of AIDS f stomach ulcers caused by Helicobacter (bacteria) g Ebola (virus) causes hemorrhagic fever Explain how pathogens are spread a cholera (bacteria) - water b tuberculosis (bacteria) - airborne c Chalara ash dieback (fungi) - airborne d malaria (protists) - animal vectors e stomach ulcers caused by Helicobacter (bacteria) - oral transmission f Ebola (virus) - body fluids The ways that pathogens are spread include: Direct contact- touching contaminated surfaces how this spread can be reduced or prevented, including: Examples: kissing, contact with bodily fluids, direct skin to skin, microorganisms from faces, infected plant material left in field . By water- drinking or coming into contact with dirty water By air- pathogens can be carried in the air and then breathed in (a common example is the droplet infection, which is when sneezing, coughing or talking expels pathogens in droplets which can be breathed in) The damage that disease causes to populations can be reduced by limiting the spread of the pathogens • Improving hygiene: Hand washing, using disinfectants, isolating raw meat, using tissues and handkerchiefs when sneezing • Reducing contact with infected individuals • Removing vectors: Using pesticides or insecticides and removing their habitat Vaccination: By injecting a small amount of a harmless pathogen into an individual's body, they can become immune to it so it will not infect them. This means they cannot pass it on to other individuals. Describe the lifecycle of a virus, including lysogenic and lytic pathways Viruses can 'survive' outside of a host - however, they require host cells to reproduce. This can be done in two ways: Lytic pathway 1. Using host cell machinery, the virus replicates its DNA. 2. Next, these are assembled to form new virus particles. 3. Once the host cell is full of virus particles, it bursts in a process called lysis. 4. The process is then repeated with nearby cells. Lysogenic pathway 1. The virus uses restriction enzymes to insert its DNA into the host cell DNA- or it can insert small circular fragments of DNA called plasmids into the host cell cytoplasm. 2. The host cell replicates, and the viral DNA is process. 3. The lytic cycle (see above) begins at this point, starting with the assembly of new viral particles in Explain how sexually transmitted infections (STIS) are spread and how this spread can be reduced or prevented, including: Sexually transmitted infections (STIS) are infections which can be spread through sexual contact, including oral and vaginal sex. They are carried in bodily fluids such as semen and vaginal fluid. Two examples are: a Chlamydia (bacteria) b HIV (virus) The spread of STIS can be reduced by using barrier methods of contraception (e.g condoms) or abstaining from sexual activity. Describe how some plants defend themselves against attack from pests and pathogens by physical barriers, including the leaf cuticle and cell wall Plants have several methods of guarding their cells and tissues against pathogens that cause disease. Some of these methods involve having physical barriers against disease, whereas others use chemicals to defend against attack from pests and pathogens: Physical barriers A thick cell lose cell wall, which impermeable to many pathogens A thick waxy cuticle on the surface of the leaf, which acts as a barrier to most pathogens Some plants are also covered in a layer of bark (e.g trees) which prevents pathogens from reaching the cells and tissues inside. Leaves can often close their stomata (pores) to stop pathogens entering the plant. Chemical barriers Cells of some plants can produce antimicrobial chemicals, proteins and enzymes Some plants can release compounds that attract larger insects than the pests, which feed on the pests and stop them eating the plant. Often, we can extract antimicrobial compounds from these plants for use in drugs such as antibiotics. Describe how plants defend themselves against attack from pests and pathogens by producing chemicals, some of which can be used to treat human diseases or relieve symptoms. Describe different ways plant diseases can be detected and identified, in the lab and in the field including the elimination of possible environmental causes, distribution analysis of affected plants, observation of visible symptoms and diagnostic testing to identify pathogens There is a wide variety of pathogens that cause plant diseases, with an equally large variety of symptoms. Detecting and identifying these diseases in the lab and in the field is important, as it helps prevent the spread of disease across an entire crop. Identifying disease in the field Plants affected by disease often have number of visible clues allowing us to identity it in the field: Chalara dieback of ash causes malformations and browning of leaves Tobacco mosaic virus causes discoloration of leaves Bacterial canker on fruit trees causes loss of leaves, stunted growth and formation of pus-filled lesions on trunk. Aphids can cause serious structural damage to plants Identifying disease in the lab 1. Cuttings are taken from the diseased plant. 2. The virus/bacterium causing the disease is grown on a culture medium/agar plate. 3. The pathogen is tested and identified using a monoclonal antibody testing kit (known as an ELISA kit). Describe how the physical barriers and chemical defences of the human body provide protection from pathogens, including: a physical barriers, including mucus, cilia and skin Produced by goblet cells in the airway, mucus traps bacteria and other pathogens before they reach the lungs and cause infection. Wafts away mucus that has trapped pathogens, to be killed by stomach acid. Provides a physical barrier against pathogens, protecting the tissues and cells beneath it from infection. b chemical defence, including lysozymes and hydrochloric acid Used by white blood cells to kill and digest bacteria Used to kill bacteria in food reaching the stomach - to prevent infection Explain the role of the specific immune system of the human body in defence against disease, including: a exposure to pathogen b the antigens trigger an immune response which causes the production of antibodies c the antigens also trigger production of memory lymphocytes d the role of memory lymphocytes in the secondary response to the antigen Explain the body's response to immunisation using an inactive form of a pathogen Vaccinations involve making an individual immune to a certain disease- they are protected against it before they have been infected. By immunising a large proportion of the population, the spread of the pathogen is reduced as there are less people to catch the disease from (called herd immunity). Naturally, when you are infected with a pathogen, you feel ill until white blood cells manufacture the correct specific antibody to combat it. Upon a secondary infection, the antibodies can be produced much quicker, so the pathogen can be destroyed and the symptoms are not felt. Vaccinations replicate the first infection. so that when the person is exposed to the real disease they do not feel any symptoms, just like in a secondary infection The vaccine contains a dead or inactivated form of the pathogen This stimulates white ood cells to produce podies complementary to antigens on the pathogen Discuss the advantages and disadvantages of immunisation, including the concept of herd immunity Explain that antibiotics can only be used to treat bacterial infections because they inhibit cell processes in the bacterium but not the host organism Antibiotics can only be used to treat bacterial infections, and not those caused by viruses, fungi or other pathogens. Bacteria are susceptible to antibiotics because antibiotics inhibit cell processes in the bacterium. However, viruses and other pathogens often use cell machinery in host cells to reproduce, and these are unaffected by antibiotics Explain the aseptic techniques used in culturing microorganisms in the laboratory, including the use of an autoclave to prepare sterile growth medium and petri dishes, the use of sterile inoculating loops to transfer microorganisms and the need to keep petri dishes and culture vials covered Microorganisms are very small, so in order for scientists to study them they need to grow many of them in the lab using nutrients (culturing them, The culture medium contains carbohydrates for energy, minerals, proteins and vitamins. There are two ways to grow microorganisms in the lab: 1. In nutrient broth solution-involves making a suspension of bacteria to be grown and mixing with sterile nutrient broth (the culture medium), stoppering the flask with cotton wool to prevent air from contaminating it and shaking regularly to provide oxygen for the growing bacteria. 2. On an agar gel plate- the agar acts as the culture medium, and bacteria grown on it form colonie on the surface. Making the plate: Hot sterilised agar jelly is poured into a sterilised Petri dish, which is left to cool and set Sterilised wire loops called inoculating loops are dipped in a solution of the microorganism and spread over the agar evenly A lid is taped on and the plate is incubated for a few days so the microorganisms can grow (stored upside down) useful calculation - as It allows us to determine the effectiveness of the antibiotic. In Part 1 of this experiment, we will grow the bacterial culture, and in Part 2 we will use T2 to examine how effective the antibiotic is: Growing the bacterial culture 1. Take a Petri dish that has been pre-poured with agar gel, and sterilise it in an autoclave before use. Use a inoculating loop (sterilised in a Bunsen Burner) to apply the bacteria being tested to the agar. Seal the top of the plate using tape. (but not completely - see section 5.17) Incubate the culture at 25 degrees C for 3 days. 2. Apply a filter paper disc soaked in antibiotic solution to the centre of the agar plate and wait for 24 hours, or until there is no further change. Calculate cross-sectional areas of bacterial cultures and clear agar jelly using mr2 Calculating the effectiveness of the antibiotic 3.- Use a ruler to measure the diameter of the circle taken up by the bacterial culture and record this measurement. Repeat for the diameter of the clear agar jelly in the centre, where the antibiotic has killed the bacteria. 4. Divide both diameters by 2 to get the radius of both these circles. Use the formula for the area of a circle (Ir2) to calculate the area of these circles. 5. Divide the area of the smaller circle by the larger, and multiply by 100. This is the percentage of the bacterial culture that has been destroyed by the antibiotic. The igher the percentage, the more effective the antibiotic. We can repeat these calculations for multiple antibiotics and bacteria, in order to determine the effectiveness of different bacteria/antibiotic combinations. This is useful as it allows doctors and scientists to work out which antibiotics are most effective for particular bacterial infections. Describe that the process of developing new medicines, including antibiotics, has many stages, including discovery, development, preclinical and clinical testing Many drugs were initially discovered in plants and microorganisms. New drugs today are mainly synthesised by chemists. They need to be tested for toxicity, efficacy (how well they carry out their role) and dose, using preclinical testing and clinical trials Plants The chemicals that plants use to kill pests and pathogens can be used to treat symptoms or human diseases Examples: Aspirin is used as a painkiller (originates from willow) Digitalis is used to treat heart problems (originates from foxgloves) Microorganisms Penicillin Alexander Fleming was growing bacteria on plates uld (Penicillium mould) ture plates, clear rings He found that the mould was producing a substance called penicillin, which killed bacteria Any new drugs being developed need to be tested to ensure they are safe and effective. Preclinical testing: using cells, tissues and live animals Clinical testing: using volunteers and patients It is first tested on healthy volunteers with a low dose to ensure there are no harmful side effects The drugs are then tested on patients to find the most effective dose To test how well works, patients are split into two groups with one group receiving the drug and one receiving a placebo (appears to look like the drug but has no active ingredient so no effect) so the effect of the new drug can be observed These can be single-blind (only the doctor knows whether the patient is receiving the drug) or double blind (neither the patient or doctor knows whether they are receiving the drug, removing any biases the doctor may have when they are recording the results). The results then need to be peer reviewed by other scientists to check for repeatability. Describe the production of monoclonal antibodies, including: Monocional antibodies are identical antibodies, that have been produced from the same immune cell. As a result of their ability to bind to only one protein antigen, they can be used to target chemicals and cells in the body and so have many different medical uses, e.g. in pregnancy testing. How are they produced: 4. The antibodies are collected and purified. a use of lymphocytes which produce desired antibodies but do not divide 1. Scientists obtain mice lymphocytes a type of white blood cell that make antibodies but cannot divide), which have been stimulated to produce a specific He mould indicating there no longer any bacteria there antibody.. 2. They are combined with tumour cells (do not make antibodies but divide rapidly), to form cell called a hybridoma. b production of hybridoma cells 3. The hybridoma can divide to produce clones of itself, which all produce the same antibody. c hybridoma cells produce antibodies as they divide Explain the use of monoclonal antibodies, including: a in pregnancy testing 1. Pregnancy tests A hormone called human chorionic gonadotrophin (hG) is present in the urine of women who are pregnant. • There are two sections of the stick. The first section has mobile antibodies complementary to the hG hormone- these antibodies are also attached to blue beads. The second section has stationary antibodies complementary to the CG hormone which are stuck down to the stick. The individual urinates on the first section, and if hCG is present it binds to the mobile antibodies attached to blue beads to form CG/antibody complexes. • They are carried in flow of liquid to the second section. • The stationary antibodies then bind to the HCG/antibody complexes As they are each bound to a blue bead, results in a blue line. . This indicates that you are pregnant. b in diagnosis including locating the position of blood clots and cancer cells and in treatment of diseases including cancer 2. In laboratories to analyse blood • They can be used to measure and monitor levels of hormones or chemicals in the blood. The monoclonal antibodies are modified so that they will bind to the molecule you are looking for. • The antibodies are also bound to a fluorescent dye. • If the molecules are in the sample then the antibodies bind to it, and the dye can be observed. An example is screening donated blood for HIV infections c the advantages of using monoclonal antibodies to target specific cells compared to drug and radiotherapy treatments. In research to find or identify certain molecules on a cell or tissue The same method as above is applied, and scientists look for a build up of the fluorescence. In the treatment of disease, e.g. cancer Cancer cells have antigens on their cell membranes known as tumour markers (not found on normal body cells), which can be targeted. There are three main ways to treat cancers using monoclonal antibodies. a) Producing monoclonal antibodies that bind to the tumour markers in order to stimulate the immune system to attack the cell. b) Using monoclonal antibodies to bind to receptor sites on the cell surface membrane of the cancer cells. This means growth-stimulating molecules cannot bind, stopping the cell from dividing. c) Using monoclonal antibodies to transport toxic drugs, chemicals or radioactive substances as they can only bind to cancer cells Describe that many non-communicable human diseases are caused by the interaction of a number of factors, including cardiovascular diseases, many forms of cancer, some lung and liver diseases and diseases influenced by nutrition Non-communicable human diseases - for example cardiovascular disease, asthma, and diabete, are caused by the interaction of a number of different factors. Cardiovascular diseases such as coronary heart disease can be caused by high dietary intake of saturated fat, combined with a sedentary (inactive) lifestyle. Several forms of cancer can be contributed to by various factors - for example, smoking greatly increases the risk of lung cancer, whereas the risk of developing breast cancer is largely due to a combination of age and genetics. Lung and liver diseases are made more likely by smoking and high alcohol intake respectively. However, other factors can play a part- especially age and genetics. As an individual gets older, they are more likely to suffer from these conditions. Vitamin and nutritional deficiencies are common in anorexic patients, as well as those who can't absorb or use nutrients properly (including patients with coeliac disease and anemia). Obesity, on the other hand, is caused by excess caloric intake (food intake), and can again be heavily influenced by genetics - some people are more likely to gain weight than others. Explain the effect of lifestyle factors on non-communicable diseases at local, national and global levels, including: a exercise and diet on obesity and malnutrition, including BMI and waist : hip calculations, using the BMI equation: () 2 mass (kg) BMI = height (m) b alcohol on liver diseases c smoking on cardiovascular diseases Obesity Eating more calories than you burn from physical activity (and everyday metabolism) causes us to put on weight. Eating a very large excess of calories, especially if a high proportion of these calories come from saturated fat, can lead to obesity and related illnesses. -Obesity is an important problem worldwide, but especially in developed countries such as the UK. Obesity can lead to developing cardiovascular disease and high blood pressure, as fat (lipid) deposits form inside blood vessels. Obesity can also contribute to developing Type 2 diabetes, as the body cannot use insulin as effectively when there is a high proportion of body fat. Government programs such as the 'sugar tax' are aimed at reducing obesity across the country. Eating fewer processed foods, less sugar, saturated fat and high calorie foods can help reduce the risk of becoming obese. Malnutrition Equally, eating significantly fewer calories than we use can lead to malnutrition, as the body will not be receiving adequate amounts of nutrients and vitamins. The symptoms can different depending the vitamin nutrient that is eficient. Malnutrition is less of a problem in developed countries like the UK, but more of an issue in underdeveloped countries where many people do not have enough money to eat. waist- hip ratio waist circumference/ hip circumference. >0.85 for women and >1 for men classifies someone as obsese Liver disease A high alcohol intake can lead to liver disease. A type of liver disease called fatty liver is common in alcoholics. It can lead to liver cancer and impaired liver function. Alcoholics often also have vitamin deficiencies (particularly vitamin B6, thiamine) The recommended weekly allowance for men and women is 14 units a week. Drinking less than this significantly reduces the risk of developing liver disease. Lung disease Smoking dramatically increases the risk of developing several lung diseases These include COPD (chronic obstructive pulmonary disease), bronchitis, pneumonia and lung cancer. Cigarette smoke contains over 40 different chemicals, all of which have different effects on the body-for example, tar can cause lung cancer and nicotine can cause high blood pressure and heart failure The UK government provide services to help and encourage smokers to quit smoking. Evaluate some different treatments for cardiovascular disease, including: a life-long medication Life-long medication There are several medications that will either reduce cholesterol or reduce blood pressure People with very high blood pressure may have to take multiple medications to reduce it They will most likely have to take these for the rest of their life b surgical procedures Surgical procedures Sometimes medication does not work effectively, and surgery may be required. Coronary arteries supply the heart muscle with oxygen, and cover the heart If these are blocked, a coronary artery bypass can be performed, where the blocked sections of the coronary artery are 'bypassed' Another method involves using a metal stent to widen arteries that have been narrowed by fat deposits (atherosclerosis) c lifestyle changes Lifestyle changes Lifestyle changes (changes to exercise, diet and other habits) are very important in preventing and treating cardiovascular disease. Reducing the amount of saturated fat we eat can reduce the risk of developing atherosclerosis (fat deposits in the arteries) and high cholesterol. Maintaining a healthy BMI can reduce strain on the heart. Taking regular exercise ensures that we remain at a healthy weight Reducing the amount of salt in the diet, and managing stress levels, can prevent high blood pressure from developing