Detailed Notes on Cell Biology - AQA Biology GCSE

Cell Structure (1.1)

Eukaryotes and Prokaryotes (1.1.1)

• All living things are made of cells: prokaryotic or eukaryotic.
  • Eukaryotic Cells (Animal and Plant):
    • Have a cell membrane, cytoplasm, and nucleus containing DNA.
  • Prokaryotic Cells (Bacteria):
    • Smaller, with cell wall, cell membrane, cytoplasm, single circular DNA strand, and plasmids.
• Organelles have specific functions within cells.
• Orders of magnitude help compare sizes of cells.
• Measurement prefixes: Centi, Milli, Micro, Nano.

Animals and Plants (1.1.2)

• Subcellular structures have specific functions:
  • Nucleus: Contains DNA coding for proteins.
  • Cytoplasm: Site of chemical reactions, contains enzymes.
  • Cell membrane: Controls entry and exit of substances.
  • Mitochondria: Site of aerobic respiration.
  • Ribosomes: Protein synthesis location.
  • Plant-specific: Chloroplasts (photosynthesis), Permanent vacuole (cell rigidity), Cell wall (strength).

Cell Specialisation (1.1.3)

• Differentiation: Cells gain structures to suit their role.
• Animal Specialised Cells:
  • Sperm: Carries DNA, streamlined for swimming.
  • Nerve: Transmits signals, has long axons.
  • Muscle: Contracts for movement, contains proteins and mitochondria.
• Plant Specialised Cells:
  • Root Hair: Absorbs water/minerals.
  • Xylem: Transports water/minerals.
  • Phloem: Transports photosynthesis products.

Microscopy (1.1.5)

• Light Microscopes: Magnify up to x2000, observe large cell structures.
• Electron Microscopes: Higher magnification/resolution, view sub-cellular structures deeply.
• Calculations in microscopy involve magnification and size formulas.

Culturing Microorganisms (1.1.6)

• Growth Methods:
  • Nutrient broth solution.
  • Agar gel plates.
• Steps for culturing include sterilization, using inoculating loops, and proper incubation.
• Microorganisms can be used to test antibiotic effects.

Cell Division (1.2)

Chromosomes (1.2.1)

• Chromosomes contain DNA/genetic information.
• 23 pairs of chromosomes in cells; sex cells have 23 total.

Mitosis and Cell Cycle (1.2.2)

• Cell cycle stages: Interphase, Mitosis, Cytokinesis.
• Essential for growth, development, and asexual reproduction.

Stem Cells (1.2.3)

• Types: Embryonic, Adult, and Plant Meristems.
• Therapeutic Cloning: Produces genetically identical cells for patient use.
• Benefits and Problems: Potential medical uses vs ethical and practical issues.

Transport in Cells (1.3)

Diffusion (1.3.1)

• Movement from high to low concentration, passive process.
• Influenced by concentration gradient and surface area.

Osmosis (1.3.2)

• Movement of water through membranes, from high to low water potential.
• Effects on animal and plant cells, modeled with experiments.

Active Transport (1.3.3)

• Movement against concentration gradient, requires energy.
• Occurs in root hair cells and gut for nutrient absorption.