AQA Biology Paper 1

1. Cell Biology

1.1 Animal and Plant Cells

  • Animal Cells: Nucleus, cytoplasm, cell membrane, mitochondria, ribosomes.

  • Plant Cells: Nucleus, cytoplasm, cell membrane, mitochondria, ribosomes, cell wall, vacuole, chloroplasts.

1.2 Specialized Cells

  • Cells are adapted for specific functions (e.g., sperm cells for reproduction, nerve cells for transmitting impulses, root hair cells for water absorption).

1.3 Microscopy

  • Light microscope: Magnifies up to x1500, uses light.

  • Electron microscope: Magnifies up to x2,000,000, uses electrons, provides higher resolution and magnification, allows viewing of sub-cellular structures.

  • Magnification formula: Magnification = \frac{Image \, size}{Actual \, size}

1.4 Cell Division

  • Mitosis: Cell division for growth and repair, produces two genetically identical daughter cells.

  • Stem Cells: Undifferentiated cells capable of developing into various specialized cell types. Embryonic stem cells (pluripotent) and adult stem cells (multipotent) exist.

1.5 Transport in and out of cells

  • Diffusion: Movement of particles from a high concentration to a low concentration (e.g., oxygen into cells).

  • Osmosis: Diffusion of water across a partially permeable membrane from a high water potential to a low water potential.

  • Active Transport: Movement of particles against a concentration gradient, requiring energy (e.g., glucose absorption in the gut).

2. Organisation

2.1 Principles of Organisation

  • Cells -> Tissues -> Organs -> Organ Systems -> Organism.

2.2 Human Digestive System

  • Mouth, oesophagus, stomach, small intestine, large intestine, rectum, anus.

  • Enzymes (amylase, protease, lipase) break down food.

2.3 Human Circulatory System

  • Heart: Pumps blood around the body in a double circulatory system.

  • Blood Components: Red blood cells (oxygen transport), white blood cells (immunity), platelets (clotting), plasma (transport medium).

  • Blood Vessels: Arteries (away from heart), veins (to heart), capillaries (exchange).

  • Coronary Heart Disease: Blockage of coronary arteries (supplying heart muscle) due to fatty deposits.

2.4 Human Breathing System

  • Trachea, bronchi, bronchioles, alveoli (gas exchange).

  • Inhalation (diaphragm contracts, ribs move up/out); Exhalation (diaphragm relaxes, ribs move down/in).

2.5 Plant Organisation

  • Leaves: Photosynthesis (palisade layer).

  • Roots: Water and mineral absorption (root hair cells).

  • Stems: Support and transport.

  • Plant Transport Systems: Xylem (water and minerals from roots to leaves), Phloem (sugars from leaves to other parts).

3. Infection and Response

3.1 Pathogens and Communicable Diseases

  • Pathogens: Microorganisms that cause disease (bacteria, viruses, fungi, protists).

  • Transmission: Air, direct contact, water, vectors.

3.2 Viral Diseases

  • Measles, HIV, Tobacco Mosaic Virus (TMV).

  • Viruses reproduce inside host cells and are difficult to treat.

3.3 Bacterial Diseases

  • Salmonella, Gonorrhoea, Crown Gall (plants).

  • Bacteria can be killed by antibiotics.

3.4 Fungal and Protist Diseases

  • Fungal: Rose black spot.

  • Protist: Malaria.

3.5 Human Defence Systems

  • Physical barriers: Skin, mucus, cilia, stomach acid.

  • Immune system: White blood cells (phagocytosis, antibody production, antitoxin production).

  • Vaccination: Introduction of weakened/dead pathogens to stimulate antibody production and provide immunity.

  • Antibiotics: Kill bacteria but not viruses.

  • Antiseptics: Kill microorganisms on surfaces; Painkillers: Treat symptoms, not cause.

3.6 Plant Diseases and Defences

  • Detection: Stunted growth, spots, discolouration, decay.

  • Physical barriers: Cell walls, waxy cuticle, bark.

  • Chemical defences: Produce antibacterial chemicals, poisons.

4. Bioenergetics

4.1 Photosynthesis

  • Equation: 6CO2 + 6H2O \xrightarrow{Light} C6H{12}O6 + 6O2

  • Endothermic reaction: Absorbs energy (light).

  • Limiting Factors: Light intensity, CO_2 concentration, temperature.

  • Leaf adaptations: Large surface area, thin, vascular bundles, stomata.

4.2 Respiration

  • Aerobic Respiration: With oxygen, in mitochondria.

    • Equation: C6H{12}O6 + 6O2 \longrightarrow 6CO2 + 6H2O \text{ (+ energy)}

    • Releases a large amount of energy.

  • Anaerobic Respiration: Without oxygen, in cytoplasm.

    • In animals: Glucose \longrightarrow Lactic \, acid \text{ (+ small energy)}

    • Causes oxygen debt.

    • In plants/yeast (fermentation): Glucose \longrightarrow Ethanol + Carbon \, dioxide \text{ (+ small energy)}

    • Releases much less energy than aerobic respiration.

4.3 Response to Exercise

  • Heart rate and breathing rate increase to supply more oxygen and glucose to muscles and remove CO_2 and lactic acid.