EDXL GCSE Biology Paper One: Topics 1-5

Key Concepts

• Cells and Control
• Genetics
• Natural Selection and Genetic Modification
• Health, Disease, and Medicines

Cells

• Types of Cells
  • Eukaryotic Cells: Have a nucleus containing DNA (e.g., plant and animal cells).
  • Prokaryotic Cells: Do not have a nucleus.
• Microscopy
  • Light microscopes show basic cell structures.
  • Electron microscopes offer higher resolution to see organelles.
• Cell Structures
  • Cell Membrane: Semi-permeable.
  • Cell Wall: Rigid structure in plants and bacteria.
  • Cytoplasm: Site of chemical reactions.
  • Mitochondria: Site of respiration.
  • Ribosomes: Protein synthesis.
  • Chloroplasts: Photosynthesis in plants.
  • Vacuole: Stores sap in plant cells.

Enzymes

• Biological catalysts that speed up chemical reactions.
• Types and Functions
  • Amylase: Breaks down starch into glucose.
  • Proteases: Break down proteins into amino acids.
  • Lipases: Break down lipids into glycerol and fatty acids.
• Lock and Key Model: Specificity of enzyme action.
• Factors Affecting Enzyme Activity
  • Temperature and pH influence enzyme activity.
  • Denaturation at extreme temperatures/pH.

Diffusion, Osmosis, and Active Transport

• Diffusion: Passive movement of molecules from high to low concentration.
• Osmosis: Diffusion of water across a semi-permeable membrane.
• Active Transport: Movement of molecules against the concentration gradient using energy.

Genetics and Cell Division

• Chromosomes and DNA
  • Humans have 23 pairs of chromosomes in diploid cells.
  • Gametes (sex cells) are haploid.
• Cell Division
  • Mitosis: Produces two identical cells for growth and repair.
  • Meiosis: Produces haploid gametes.
• Stem Cells
  • Unspecialized cells that can differentiate into specialized cells.
  • Ethical considerations in stem cell research.

Nervous System

• Components
  • CNS: Brain and spinal cord.
  • PNS: Peripheral nerves.
• Reflex Actions: Rapid, involuntary responses.
• Parts of the Brain
  • Cerebral Cortex: Higher functions like memory and problem-solving.
  • Cerebellum: Motor skills and balance.
  • Medulla: Controls unconscious actions.

Eye Structure and Function

• Accommodation: Ability of the eye to focus on objects at various distances.
• Myopia and Hyperopia: Short and long-sightedness; corrected with lenses or surgery.

Reproduction

• Sexual Reproduction: Involves meiosis and genetic variation.
• Asexual Reproduction: Produces clones via mitosis.

Inheritance

• Genotype: Genetic makeup.
• Phenotype: Observed characteristics.
• Allel Types: Dominant and recessive.
• Use of Punnett Squares for genetic predictions.

Evolution and Genetic Modification

• Darwin's Evolution: Natural selection favors advantageous traits.
• Lamarck's Theory: Early ideas on acquired characteristics.
• Bacterial Resistance: Evidence of evolution in action.
• Genetic Engineering: Modifying organisms for desirable traits.

Health and Disease

• Non-communicable: Caused by internal factors (e.g., cardiovascular disease).
• Communicable: Caused by pathogens (e.g., viruses, bacteria).
• Immune System: Fights off pathogens with white blood cells and antibodies.

Medicines and Drugs

• Antibiotics: Treat bacterial infections but not viruses.
• Drug Development: Involves extensive testing for safety and efficacy.

Additional Topics for Triple Science

• Monoclonal Antibodies: Using clones to produce specific antibodies.
• Genetic Engineering Techniques: Advanced methods for modifying organisms.