Metabolism and Survival: overview of SQA Higher Biology Area 2

Metabolism and Survival is the second of the three areas of SQA Higher Biology. It examines how cells control and power their chemistry, how organisms survive changing or harsh conditions, and how the metabolism of microorganisms is studied and exploited. This page maps the six key areas and shows how they connect.

The six key areas

Metabolic pathways and control

Metabolism is an integrated network of anabolic and catabolic reactions controlled by enzymes (induced fit), inhibitors (competitive and non-competitive) and feedback inhibition, organised by membranes.

Cellular respiration

Glycolysis, the citric acid cycle and the electron transport chain release energy from glucose to make ATP; fermentation provides a little ATP when oxygen is absent.

Metabolic rate, conformers and regulators

Metabolic rate is measured by oxygen use, carbon dioxide production or heat; conformers save energy but depend on stable conditions, while regulators spend energy to stay active across more niches.

Maintaining metabolism and dormancy

Predictive and consequential dormancy, hibernation, aestivation, daily torpor and migration help organisms survive when conditions are too harsh for normal metabolism.

Environmental control of metabolism in microorganisms

Microorganisms grow through lag, log, stationary and death phases, making primary and secondary metabolites, with conditions controlled in fermenters.

Genetic control of metabolism

Wild strains are improved by mutagenesis and selective breeding, and recombinant DNA technology uses vectors, restriction endonucleases, ligase and marker genes to make useful products.

How to study Area 2

1. Sequence the respiration pathways. Know the location, inputs and outputs of glycolysis, the citric acid cycle and the electron transport chain.
2. Distinguish the control mechanisms. Competitive, non-competitive and feedback inhibition are easy marks if defined precisely.
3. Compare strategies. Conformer versus regulator, and the forms of dormancy and migration, are often tested as costs and benefits.
4. Drill the microbiology. Growth-curve phases and the recombinant DNA toolkit recur in the question paper.

For the official course specification

The SQA publishes the full Higher Biology course specification, specimen and past papers, and marking instructions at sqa.org.uk. Always revise from the current specification and SQA past papers.