GCE Advanced Level (A-Levels) Biology Syllabus

Biology syllabus — full chapter and topic list

Expand any chapter to see its topics and sub-topics. This is the whole examinable outline for Biology in GCE Advanced Level (A-Levels), not a summary of it.

1. 1

   Biological Molecules and Cells

   4 topics

   • Biological Molecules
     • Carbohydrates, lipids and proteins
     • Enzymes and the induced-fit model
     • Nucleic acids: DNA, RNA and ATP
     • Water and inorganic ions
   • Cell Structure
     • Eukaryotic and prokaryotic cells
     • Organelles and their functions
     • Microscopy and magnification
   • Cell Membranes and Transport
     • Fluid mosaic model
     • Diffusion, osmosis and active transport
   • Cell Division
     • The cell cycle and mitosis
     • Meiosis and genetic variation
2. 2

   Exchange, Transport and Immunity

   3 topics

   • Exchange Surfaces
     • Surface area to volume ratio
     • Gas exchange in humans, fish and plants
   • Mass Transport Systems
     • The heart and circulatory system
     • Haemoglobin and oxygen dissociation curves
     • Transport in plants: xylem and phloem
   • Immunity
     • Phagocytosis and the specific immune response
     • Antibodies, vaccination and herd immunity
     • Antigenic variation and monoclonal antibodies
3. 3

   Genetics and Variation

   4 topics

   • DNA, Genes and Protein Synthesis
     • The genetic code and gene structure
     • Transcription and translation
     • Gene mutations
   • Inheritance
     • Monohybrid and dihybrid crosses
     • Sex linkage and codominance
     • Chi-squared analysis of genetic data
   • Variation and Evolution
     • Natural selection and types of selection
     • The Hardy-Weinberg principle
     • Speciation and genetic drift
   • Biodiversity and Classification
     • Taxonomy and phylogeny
     • Measuring biodiversity and index of diversity
4. 4

   Energy Transfers and Ecosystems

   4 topics

   • Photosynthesis
     • Light-dependent reactions
     • The Calvin cycle
     • Limiting factors
   • Respiration
     • Glycolysis and the link reaction
     • The Krebs cycle and oxidative phosphorylation
     • Anaerobic respiration
   • Ecosystems and Energy Flow
     • Food chains, food webs and trophic levels
     • Productivity and energy transfer efficiency
   • Nutrient Cycles and Succession
     • The carbon and nitrogen cycles
     • Ecological succession
5. 5

   Control Systems and Gene Technology

   4 topics

   • Nervous Coordination
     • Resting and action potentials
     • Synaptic transmission
     • Receptors and reflexes
   • Homeostasis
     • Negative feedback principles
     • Control of blood glucose
     • Osmoregulation and the kidney
   • Control of Gene Expression
     • Transcription factors and epigenetics
     • Stem cells and totipotency
   • Gene Technology
     • Recombinant DNA technology
     • PCR, gene probes and DNA profiling
     • Genome sequencing and applications

Biology flashcards for GCE Advanced Level (A-Levels)

22 of 78 cards from the Biology deck — real questions with worked answers.

1. What is the role of hydrogen bonding in water that makes it a good coolant and habitat?

   Hydrogen bonds between polar water molecules give water a high specific heat capacity (resists temperature change) and high latent heat of vaporisation (evaporation provides cooling), keeping aquatic environments thermally stable.

2. Name the monomer, type of bond, and reaction that links the monomers in a polysaccharide.

   Monomer = monosaccharide (e.g. $\alpha$-glucose); bond = glycosidic bond; formed by a condensation reaction (removing water).

3. Compare the structure of starch (amylose), glycogen and cellulose.

   Amylose: $\alpha$-glucose, $1,4$ glycosidic bonds, helical/unbranched. Glycogen: $\alpha$-glucose, $1,4$ and $1,6$ bonds, highly branched. Cellulose: $\beta$-glucose, alternate molecules inverted, straight chains held by hydrogen bonds into microfibrils.

4. Describe the biochemical (food) tests for reducing sugar, non-reducing sugar, starch, protein and lipids.

   Reducing sugar: Benedict's, blue $\to$ brick-red precipitate on heating. Non-reducing sugar: boil with acid, neutralise, then Benedict's. Starch: iodine in potassium iodide, orange $\to$ blue-black. Protein: biuret, blue $\to$ purple. Lipid: emulsion test with ethanol, white emulsion.

5. What four structural levels describe a protein, and which bonds maintain the tertiary structure?

   Primary (amino acid sequence), secondary ($\alpha$-helix/$\beta$-pleated sheet from hydrogen bonds), tertiary (3D fold), quaternary (multiple polypeptides). Tertiary structure is held by hydrogen bonds, ionic bonds, disulfide bridges and hydrophobic interactions.

6. State the induced-fit model of enzyme action and how it lowers activation energy.

   The active site is not perfectly complementary at first; substrate binding induces a conformational change so the active site moulds around the substrate, forming an enzyme-substrate complex that strains/positions bonds, lowering the activation energy.

7. Distinguish competitive from non-competitive inhibition.

   Competitive: inhibitor is similar in shape to substrate and binds the active site; effect reduced by raising substrate concentration. Non-competitive: inhibitor binds elsewhere (allosteric site), changing the active site's shape; effect not overcome by more substrate.

8. List the key features of a fluid-mosaic membrane.

   A phospholipid bilayer (fluid) with embedded and surface proteins (mosaic), cholesterol regulating fluidity, glycoproteins and glycolipids for cell recognition, and channel/carrier proteins for transport.

9. Compare the resolution and magnification of light, TEM and SEM microscopes.

   Light: resolution ~$200\,\text{nm}$, magnification up to ~$\times 1500$, living specimens, colour. TEM: resolution ~$0.5\,\text{nm}$, very high magnification, 2D internal detail. SEM: resolution ~$3\text{–}10\,\text{nm}$, 3D surface images. Electron microscopes need a vacuum (dead specimens).

10. Give the magnification equation and rearrange it for actual size.

    $$\text{magnification} = \frac{\text{image size}}{\text{actual size}}$$ so $\text{actual size} = \dfrac{\text{image size}}{\text{magnification}}$. Remember $1\,\text{mm} = 1000\,\mu\text{m} = 10^{6}\,\text{nm}$.

11. State the function of the rough ER, Golgi apparatus and mitochondria.

    Rough ER: synthesises and transports proteins (ribosomes on surface). Golgi apparatus: modifies, packages and sorts proteins/lipids into vesicles, forms lysosomes. Mitochondria: site of aerobic respiration producing ATP.

12. Define diffusion, osmosis and active transport.

    Diffusion: net movement of particles from high to low concentration down a gradient (passive). Osmosis: net movement of water across a partially permeable membrane from higher to lower water potential. Active transport: movement against a gradient using carrier proteins and ATP.

13. What is water potential, and how do solutes and pressure affect it?

    Water potential ($\Psi$) is the tendency of water to move; pure water at standard conditions has $\Psi = 0$. Adding solute lowers it (solute potential is negative); $\Psi$ values in cells are therefore negative. Water moves from higher (less negative) to lower (more negative) $\Psi$.

14. Distinguish facilitated diffusion from simple diffusion.

    Simple diffusion: small/non-polar molecules pass directly through the bilayer down a gradient. Facilitated diffusion: large or charged molecules move down a gradient through channel or carrier proteins, still passive (no ATP).

15. Outline the role of co-transport in glucose absorption in the ileum.

    Sodium is actively pumped out of the epithelial cell into the blood, creating a low intracellular $\ce{Na+}$. $\ce{Na+}$ then diffuses in from the lumen through a co-transporter protein, carrying glucose against its gradient; glucose then leaves into the blood by facilitated diffusion.

16. Name the stages of the cell cycle in order.

    Interphase ($G_1$ growth, S DNA replication, $G_2$ growth) $\to$ mitosis (prophase, metaphase, anaphase, telophase) $\to$ cytokinesis.

17. Describe what happens in each stage of mitosis.

    Prophase: chromosomes condense, spindle forms, nuclear envelope breaks down. Metaphase: chromosomes align on the equator. Anaphase: sister chromatids pulled to opposite poles by spindle fibres. Telophase: nuclear envelopes reform around two sets of chromosomes.

18. Give the mitotic index formula.

    $$\text{mitotic index} = \frac{\text{number of cells in mitosis}}{\text{total number of cells}}$$ (often expressed as a decimal or percentage).

19. How does meiosis generate genetic variation?

    Two ways: independent (random) assortment of homologous chromosomes/chromatids at metaphase I and II, and crossing over (recombination) of alleles between homologous chromosomes at prophase I. Random fertilisation adds further variation.

20. State the relationship between surface area to volume ratio and the need for exchange surfaces.

    As an organism gets larger, its surface area to volume ratio decreases, so diffusion across the surface alone cannot meet metabolic demands; specialised exchange surfaces (large area, thin, good blood supply) and mass transport systems are required.

21. State Fick's law and what each term means for diffusion rate.

    $$\text{rate of diffusion} \propto \frac{\text{surface area} \times \text{concentration difference}}{\text{diffusion distance}}$$ Rate increases with greater surface area and steeper concentration gradient, and decreases with longer diffusion distance.

22. Describe how the alveoli are adapted for efficient gas exchange.

    Large total surface area, walls one flattened epithelial cell thick (short diffusion distance), surrounded by a dense capillary network and ventilation maintaining steep concentration gradients, and moist surface for gases to dissolve.

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