Detailed Notes: Topic 1 Cell Biology - AQA Biology GCSE

Overview

• Focus on cell biology for GCSE AQA Biology.
• Covers eukaryotic and prokaryotic cells, cell structure, differentiation, cell division, transport mechanisms, and culturing microorganisms.

Cell Structure

Eukaryotes and Prokaryotes (1.1.1)

• Eukaryotic Cells: Animal and plant cells
  • Have a cell membrane, cytoplasm, and nucleus containing DNA.
• Prokaryotic Cells: Bacterial cells
  • Smaller, with cell wall, cell membrane, cytoplasm, single circular strand of DNA, and plasmids.
• Orders of Magnitude: Used to compare sizes of objects.
• Prefixes: Centi, Milli, Micro, Nano.

Animals and Plants (1.1.2)

• Animal Cells:
  • Nucleus: Contains DNA for protein synthesis.
  • Cytoplasm: Site for chemical reactions.
  • Cell membrane: Regulates entry and exit.
  • Mitochondria: Site of aerobic respiration.
  • Ribosomes: Protein synthesis.
• Plant Cells:
  • Chloroplasts: Photosynthesis site, contains chlorophyll.
  • Vacuole: Contains cell sap, maintains rigidity.
  • Cell wall: Made of cellulose, provides strength.

Cell Specialisation (1.1.3)

• Differentiation: Cells gain structures to suit roles.
• Specialised Animal Cells:
  • Sperm Cells: Streamlined for carrying DNA.
  • Nerve Cells: Transmit electrical signals quickly.
  • Muscle Cells: Contract for movement.
• Specialised Plant Cells:
  • Root Hair Cells: Absorb water/minerals.
  • Xylem Cells: Transport water/minerals.
  • Phloem Cells: Transport photosynthesis products.

Cell Differentiation (1.1.4)

• Stem Cells: Can differentiate and divide.
• Animal Cells: Differentiate early, limited division.
• Plant Cells: Retain differentiation ability.

Microscopy (1.1.5)

• Light Microscope: Magnifies images using light, max x2000 magnification.
• Electron Microscope: Uses electrons, deeper sub-cellular view, higher magnification.

Culturing Microorganisms (1.1.6)

• Growing Methods:
  • Nutrient Broth Solution: Suspended bacteria.
  • Agar Gel Plate: Grow colonies on surface.
• Sterilization: Essential to prevent contamination.

Cell Division (1.2)

Chromosomes (1.2.1)

• Chromosomes: Contain DNA, 23 pairs in humans.
• Mitosis and Cell Cycle (1.2.2):
  • Interphase: Cell growth and DNA replication.
  • Mitosis: Chromosome division.
  • Cytokinesis: Formation of daughter cells.
• Importance: Growth, repair, asexual reproduction.

Stem Cells (1.2.3)

• Types:
  • Embryonic: Can form any cell.
  • Adult: Limited types (e.g., blood cells).
  • Meristems in Plants: Differentiate throughout life.
• Therapeutic Cloning: Avoids rejection issues, ethical concerns.

Transport in Cells (1.3)

Diffusion (1.3.1)

• Passive Movement: Higher to lower concentration.
• Influencing Factors: Concentration gradient, temperature, surface area.

Osmosis (1.3.2)

• Water Movement: Across a membrane from dilute to concentrated solution.
• Effects: Burst or shrivel cells depending on solution.

Active Transport (1.3.3)

• Energy Required: Moves particles against gradient.
• Examples:
  • Root Hairs: Absorb minerals.
  • Gut: Moves glucose into bloodstream.

Additional Information

• Standard Form: Used for large/small numbers in calculations.
• Antibiotics Testing: Observing effects on bacterial growth on agar plates.