AQA Combined Science Biology Paper 1 Mind Maps - Higher Level Notes

Cells and Cell Biology

Ever wondered what makes you different from a plant or a bacterium? It all comes down to cell structure and what's inside them. Eukaryotic cells (like yours) have a proper nucleus containing DNA, whilst prokaryotic cells (bacteria) just have their DNA floating about freely.

Animal cells contain mitochondria for aerobic respiration, a nucleus with genetic material, cytoplasm where chemical reactions happen, and ribosomes that make proteins. Plant cells have all of these plus chloroplasts for photosynthesis and a permanent vacuole filled with cell sap.

Some cells become specialists through cell specialisation. Root hair cells have a massive surface area for absorbing water, muscle cells are packed with mitochondria for energy, and sperm cells have long tails for swimming. Stem cells are the ultimate multitaskers - they can turn into any type of cell your body needs.

Top Tip: When using a microscope, always start with the lowest magnification and work your way up. This prevents you from accidentally damaging the slide!

Diffusion moves particles from high to low concentration without needing energy, whilst active transport does the opposite but requires energy. Osmosis specifically moves water through membranes. All three processes are crucial for keeping your cells alive and functioning.

Heart, Circulation and Digestion

Your heart is basically a double pump that never gets a break - it beats roughly 100,000 times every single day! The right side pumps blood to your lungs, whilst the left side pumps oxygenated blood around your entire body through the systematic circulation.

Arteries carry blood away from your heart under high pressure with thick, elastic walls. Veins bring blood back with thinner walls and valves to prevent backflow. Capillaries are tiny vessels where the actual exchange of nutrients and oxygen happens between blood and tissues.

Your digestive system breaks down food using enzymes - amylase tackles starch, protease handles proteins, and lipase deals with fats. The small intestine has millions of villi (tiny folds) that massively increase surface area for absorbing nutrients into your bloodstream.

Remember: Enzymes are like molecular scissors - each type only cuts specific substances, and they work best at particular temperatures and pH levels.

Coronary heart disease happens when fatty deposits clog up the arteries supplying your heart muscle. Treatments include statins to reduce cholesterol, stents to keep arteries open, or bypass surgery for severe cases.

Disease, Immunity and Drugs

Pathogens are basically microscopic troublemakers that cause infectious diseases - bacteria, viruses, fungi, and protists all fall into this category. Your body has some brilliant defence mechanisms including your skin as a barrier, stomach acid that kills germs, and white blood cells that fight infections.

White blood cells are your body's security team. They can engulf pathogens through phagocytosis or produce antibodies that specifically target particular diseases. Once you've had a disease, these antibodies stick around ready to fight it off faster next time.

Vaccinations work by introducing dead or weakened pathogens into your body, training your immune system to recognise and destroy the real thing without making you ill. This is why vaccines are so effective at preventing diseases like measles and polio.

Antibiotics only work against bacterial infections - they're completely useless against viruses because viruses live and reproduce inside your own cells. Unfortunately, some bacteria are developing antibiotic resistance through natural selection, making infections harder to treat.

Key Point: Never demand antibiotics for viral infections like colds or flu - they won't help and contribute to dangerous antibiotic resistance.

All new drugs undergo rigorous testing on cells, animals, and finally humans before being approved for public use.