Genetic Engineering and DNA Structure

Genetic engineering is a process that involves manipulating an organism's DNA. The steps of genetic engineering in biology include:

1. Identifying and extracting a gene from a chromosome using enzymes
2. Removing a plasmid from bacteria
3. Inserting the gene into the plasmid
4. Inserting the modified plasmid into a new bacterial cell
5. Growing the bacteria to produce more copies of the gene

Highlight: These 5 steps of genetic engineering form the basis of many biotechnology applications.

DNA structure and protein production:

• DNA is a double helix structure composed of complementary base pairs: Adenine-Thymine and Cytosine-Guanine.
• Genes are sections of DNA that code for specific proteins.
• The order of bases on the DNA strand determines the sequence of amino acids in proteins.

Definition: mRNA (messenger RNA) is a complementary copy of DNA that carries genetic information to ribosomes for protein synthesis.

Highlight: Understanding the stages of genetic engineering and DNA structure is crucial for comprehending modern biotechnology techniques.

Cell Structure and Functions

Different types of cells (animal, plant, fungal, and bacterial) have distinct structures, but share some common components:

1. Nucleus: Controls and stores DNA
2. Cytoplasm: Site of chemical reactions
3. Ribosomes: Responsible for protein synthesis
4. Mitochondria: Site of aerobic respiration
5. Cell membrane: Controls entry and exit of substances

Plant cells have additional structures:

• Cell wall: Provides support and protection
• Chloroplasts: Site of photosynthesis
• Large vacuole: Maintains cell turgidity

Bacterial cells have unique features:

• Plasmid: A ring of DNA
• Lack of membrane-bound organelles

Highlight: The location and function of cellular components are crucial for understanding biological processes like protein synthesis and respiration.

Example: Enzymes' role in protein synthesis is primarily carried out in ribosomes, where amino acids are linked together based on the mRNA sequence.

Cell Membrane and Transport Mechanisms

The cell membrane is a selectively permeable barrier that controls the movement of substances in and out of the cell. There are several transport mechanisms:

1. Diffusion: Passive movement of molecules from high to low concentration
2. Osmosis: Passive movement of water molecules across a semi-permeable membrane
3. Active transport: Movement of ions or molecules against the concentration gradient, requiring energy

Example: Carbon dioxide moves out of cells by diffusion.

Cell responses to osmotic conditions:

• Plant cells:
  • High water concentration: Turgid
  • Equal concentration: Normal
  • Low water concentration: Plasmolysed
• Animal cells:
  • High water concentration: May burst
  • Equal concentration: Normal
  • Low water concentration: Shrink

Highlight: Plant cells do not burst in high water concentrations due to their cell wall.

Proteins and Enzymes

Proteins have various functions in organisms, including:

• Hormones
• Hemoglobin
• Receptors
• Enzymes
• Antibodies

Enzymes are biological catalysts that speed up chemical reactions in cells. They work by:

1. Binding to a substrate at the active site
2. Facilitating the reaction (either degradation or synthesis)
3. Releasing the products

Definition: The enzyme function is to lower the activation energy required for biochemical reactions.

Factors affecting enzyme activity:

• Temperature: Enzymes have an optimum temperature (e.g., 37°C for human enzymes)
• pH: Each enzyme has an optimal pH range

Highlight: If temperature or pH exceeds the optimum, enzymes can become denatured, changing the shape of their active site and stopping the reaction.

Example: In protein synthesis, enzymes play crucial roles in various steps, including DNA replication, transcription, and translation.

Respiration and Energy Production in Cells

Respiration is the process by which cells release energy from glucose. This energy is stored in the form of ATP, a high-energy compound. There are two main types of respiration:

1. Aerobic respiration: Requires oxygen and occurs in the mitochondria. It produces 38 ATP molecules per glucose molecule.

2. Anaerobic respiration: Does not require oxygen and occurs in the cytoplasm. It produces only 2 ATP molecules per glucose molecule.

Highlight: The difference between aerobic and anaerobic respiration processes lies in their oxygen requirements and energy yield.

Anaerobic respiration in plants and yeast follows a different pathway compared to animals:

Example: In plants and yeast, the anaerobic respiration equation is: Glucose → 2 Pyruvate → CO₂ + Ethanol + 2 ATP

Vocabulary: Fermentation is the term used for anaerobic respiration in animals, plants, and yeast.

Where does anaerobic respiration occur? It takes place in the cytoplasm of cells, unlike aerobic respiration which occurs in mitochondria.

Definition: The anaerobic respiration word equation for animals is: Glucose → 2 Pyruvate ↔ 2 Lactate + 2 ATP