Scottish Advanced Higher 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 Scottish Advanced Higher, not a summary of it.

1. 1

   Cells and Proteins

   4 topics

   • Laboratory techniques for biologists
     • Microscopy and cell culture
     • Separation and quantification of proteins
   • Proteins
     • Protein structure and conformation
     • Membrane proteins and transport
   • Detecting and amplifying stimuli
     • Signal transduction
     • Phosphorylation and second messengers
   • Communication between cells
     • Hydrophobic and hydrophilic signalling molecules
     • Neurotransmitters and the nervous system
2. 2

   Organisms and Evolution

   4 topics

   • Field techniques and sampling
     • Sampling methods and identification
     • Ethical considerations in fieldwork
   • Evolution and natural selection
     • Variation and sexual selection
     • Genetic drift and gene flow
   • Variation and sexual reproduction
     • Sexual versus asexual reproduction
     • Parasitism and coevolution
   • Social behaviour
     • Altruism and kin selection
     • Cooperative hunting and defence
3. 3

   Investigative Biology

   3 topics

   • Scientific principles and process
     • Hypotheses and predictions
     • Independent, dependent and confounding variables
   • Experimentation and controls
     • Positive and negative controls
     • Replication and sample size
   • Reporting and critical evaluation
     • Statistical concepts and significance
     • Evaluation of scientific literature
4. 4

   Project and Practical Investigation

   3 topics

   • Research and planning
     • Literature review
     • Experimental design and risk assessment
   • Data collection and analysis
     • Data tables and graphing
     • Treatment of uncertainty and error
   • Dissertation
     • Structure and scientific argument
     • Conclusions and evaluation

Biology flashcards for Scottish Advanced Higher

22 of 51 cards from the Biology deck — real questions with worked answers.

1. In SDS-PAGE used to separate proteins, what does SDS do to the proteins before electrophoresis?

   SDS (sodium dodecyl sulfate) is a detergent that denatures proteins and coats them with a uniform negative charge, so they separate by molecular size alone rather than by native charge or shape.

2. What is the purpose of a buffer solution in laboratory techniques, and how does it work?

   A buffer resists changes in pH when small amounts of acid or alkali are added. It works because it contains a weak acid and its conjugate base (or weak base and conjugate acid) that absorb added $\ce{H+}$ or $\ce{OH-}$ ions.

3. State the Beer–Lambert law as used in colorimetry and give the equation.

   Absorbance is directly proportional to the concentration of the absorbing substance and the path length: $$A = \varepsilon c l$$ where $A$ is absorbance, $\varepsilon$ is the molar absorption coefficient, $c$ is concentration and $l$ is path length.

4. In centrifugation, where do the densest particles end up, and what is the resulting layered material called?

   The densest particles sediment to the bottom forming the pellet; the remaining liquid above is the supernatant.

5. Distinguish between affinity chromatography and gel-filtration (size-exclusion) chromatography for separating proteins.

   Affinity chromatography separates a protein by its specific binding to an immobilised ligand on the column matrix. Gel-filtration separates proteins by size: small molecules enter the gel beads and are retarded, while large molecules pass through faster and elute first.

6. What is the difference between a linear, a logarithmic and a semi-logarithmic scale when presenting biological data?

   A linear scale has equal intervals representing equal amounts. A logarithmic scale has intervals representing equal multiplicative factors (e.g. powers of 10). A semi-logarithmic plot uses a log scale on one axis (often the y-axis) and a linear scale on the other, useful for exponential data such as cell growth.

7. Define the isoelectric point (pI) of a protein.

   The pI is the pH at which a protein carries no net electrical charge, so its positive and negative charges balance; at this pH the protein will not migrate in an electric field and is least soluble.

8. Name the four levels of protein structure.

   Primary (amino acid sequence), secondary (regular local folding such as $\alpha$-helices and $\beta$-pleated sheets), tertiary (overall 3D folding of a single polypeptide), and quaternary (arrangement of multiple polypeptide subunits).

9. What type of bond forms the primary structure of a protein, and between which groups does it form?

   A peptide bond, a covalent bond formed by a condensation reaction between the carboxyl group ($\ce{-COOH}$) of one amino acid and the amino group ($\ce{-NH2}$) of the next, releasing water.

10. Which interactions stabilise the secondary structure of proteins ($\alpha$-helix and $\beta$-sheet)?

    Hydrogen bonds between the carbonyl oxygen ($\ce{C=O}$) of one peptide bond and the amino hydrogen ($\ce{N-H}$) of another along the polypeptide backbone.

11. List the four types of interaction that maintain the tertiary structure of a protein.

    Hydrogen bonds, ionic bonds (between charged R-groups), hydrophobic interactions (non-polar R-groups clustering away from water), and disulfide bridges (covalent $\ce{-S-S-}$ bonds between cysteine residues).

12. What is an allosteric protein, and what is the difference between positive and negative modulators?

    An allosteric protein has a binding site distinct from its active/functional site whose occupation changes the protein's conformation and activity. A positive modulator increases activity/affinity, while a negative modulator decreases it.

13. Explain the difference between competitive and non-competitive (allosteric) enzyme inhibition.

    A competitive inhibitor binds the active site, competes with substrate, and its effect is overcome by increasing substrate concentration. A non-competitive inhibitor binds an allosteric site, changing the active site's shape; its effect is not reversed by adding more substrate.

14. What is meant by reversible phosphorylation as a means of controlling protein activity?

    A protein kinase adds a phosphate group from ATP to a protein, and a phosphatase removes it. Phosphorylation changes the protein's conformation and so switches its activity on or off, allowing rapid reversible control.

15. In sensory cell signalling, distinguish between a chemical (ligand-gated) ion channel and a voltage-gated ion channel.

    A ligand-gated channel opens when a specific signal molecule binds to it, whereas a voltage-gated channel opens in response to a change in membrane potential across the cell.

16. Describe the role of a G-protein coupled receptor in transducing an external signal.

    When a ligand binds the receptor, the receptor activates an associated G-protein, which then activates (or inhibits) a membrane-bound effector enzyme, triggering production of a second messenger that relays the signal inside the cell.

17. What is a second messenger, and give a common example.

    A second messenger is an intracellular signalling molecule that amplifies and relays a signal received at the cell surface to bring about a response. A common example is cyclic AMP (cAMP), produced from ATP by adenylate cyclase.

18. Explain how signal amplification is achieved in a hormone signalling cascade.

    A single receptor–ligand binding event activates an enzyme that produces many second-messenger molecules, each of which activates several further enzymes in a cascade, so the original small signal is amplified into a large cellular response.

19. In the detection of light by rod cells, what is the light-absorbing pigment and what happens when it absorbs a photon?

    The pigment is rhodopsin (opsin plus retinal). Absorbing a photon causes retinal to change shape (cis to trans), activating opsin, which triggers a signal cascade that hyperpolarises the rod cell and alters neurotransmitter release.

20. Distinguish between the four main types of cell signalling: endocrine, paracrine, autocrine and direct (contact-dependent).

    Endocrine: hormones travel in the blood to distant target cells. Paracrine: signals act on nearby cells. Autocrine: a cell signals to itself. Direct/contact-dependent: signalling requires physical contact between cells (e.g. via membrane-bound molecules or gap junctions).

21. Why can steroid (lipid-soluble) hormones diffuse directly into the cell, and where are their receptors located?

    Because they are hydrophobic, steroid hormones pass directly through the phospholipid bilayer. Their receptors are intracellular (in the cytoplasm or nucleus), and the hormone–receptor complex typically acts as a transcription factor regulating gene expression.

22. What is the difference between hydrophilic and hydrophobic signalling molecules in terms of how they reach their receptors?

    Hydrophilic (water-soluble) signals cannot cross the membrane and bind receptors on the cell surface. Hydrophobic (lipid-soluble) signals diffuse through the membrane to bind intracellular receptors.

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