AQA GCSE Biology Paper 1 Overview

Topics Covered

• Cells
• Organization
• Infection and Response
• Bioenergetics

This guide is suitable for:

• Higher and Foundation tier
• Double Combined Trilogy
• Triple or Separate Biology

Cells

• All Life Consists of Cells

  • Visible with light microscope: only nucleus clearly visible.
  • Electron microscopes: see subcellular structures due to higher resolution.
  • Cell size calculation:
    • Formula: Magnification = Image Size / Object Size
    • Rearrange to find actual size.

• Types of Cells

  • Eukaryotic: Have nucleus (e.g., plant and animal cells).
  • Prokaryotic: No nucleus.

• Cell Structures

  • Cell membrane: Semi-permeable.
  • Cell wall (plants/bacteria): Rigid structure.
  • Cytoplasm: Site for chemical reactions.
  • Mitochondria: Respiration.
  • Ribosomes: Protein synthesis.
  • Chloroplasts (plants): Photosynthesis.
  • Vacuole (plants): Stores sap.

• Specialized Cells and Stem Cells

  • Specialized cells: Nerve, muscle, root hair, xylem, phloem.
  • Stem cells: Non-specialized, found in embryos and bone marrow.
  • Applications: Treat diabetes, paralysis. Ethical considerations exist.

Organization

• Cells form tissues, tissues form organs, organs form organ systems.
• Digestive System
  • Breaks down food with acids, bile, and enzymes.
  • Enzymes: Biological catalysts, specific to molecules (lock and key principle).

Infection and Response

• Pathogens

  • Types: Viruses, bacteria, fungi, protists.
  • Viruses: Cannot reproduce alone, use host cells (e.g., measles, HIV).
  • Bacteria: Release toxins (e.g., salmonella, gonorrhea).
  • Fungi: Cause conditions like athlete's foot.
  • Protists: Includes malaria, spread by vectors.

• Body's Defenses

  • Skin, mucus, digestive enzymes.
  • White blood cells: Lymphocytes produce antibodies, phagocytes ingest pathogens.

• Vaccines: Introduce dead/inert pathogens to stimulate immunity.

• Antibiotics: Kill bacteria, not viruses. Resistance is a concern.

Bioenergetics

• Photosynthesis

  • Occurs in chloroplasts.
  • Equation: Light energy converts CO2 and water into glucose and oxygen.
  • Factors affecting rate: Light, temperature, CO2 concentration.

• Cell Respiration

  • Aerobic: Uses oxygen, efficient.
  • Anaerobic: No oxygen, produces lactic acid, less efficient.

• Metabolism

  • Sum of all biochemical reactions.
  • Includes respiration, synthesis, and breakdown of molecules.

Practical Experiments

• Culturing Bacteria: Use aseptic techniques, calculate growth areas.
• Osmosis: Measure mass change in plant tissues in different sugar solutions.
• Enzyme Activity: Test with different temperatures/pH using iodine and starch.
• Transpiration and Photosynthesis Rates: Use pondweed and bubbler method.

Circulatory System

• Double circulatory system: heart, arteries, veins, capillaries.
• Blood composition: red cells, white cells, platelets.
• Heart function: Valves prevent backflow, coronary arteries supply heart muscle.

Plant Structures

• Leaf Structure

  • Layers: Cuticle, epidermis, palisade mesophyll, spongy mesophyll.
  • Functions: Photosynthesis, gas exchange, water regulation.

• Transport in Plants

  • Xylem: Water transport (transpiration).
  • Phloem: Nutrient transport (translocation).

Miscellaneous

• Disease Prevention: Health impacts, lifestyle factors, carcinogens.
• Biotechnology: Drug synthesis, antibody production, mRNA vaccines.