OCR A Level Biology A Module 5: Communication, Homeostasis and Energy Exam Questions

About OCR A Level Biology A Module 5: Communication, Homeostasis and Energy

Module 5 of OCR A Level Biology A, Communication, Homeostasis and Energy, explains how organisms coordinate responses and supply themselves with energy. It covers negative feedback and thermoregulation, excretion by the liver and kidney, nerve impulses and synapses, hormonal control including blood glucose, plant hormones and animal responses including muscle contraction, then the biochemistry of photosynthesis and respiration. It draws on membranes and enzymes from Module 2 and transport from Module 3. Examiners often test the action potential, kidney function, insulin secretion, the sliding filament model, the Calvin cycle, chemiosmosis and respiratory quotient calculations.

What you need to know

• 5.1.1 Cell signalling, homeostasis by negative and positive feedback, and thermoregulation in ectotherms and endotherms.
• 5.1.2 Liver structure and functions including deamination and the ornithine cycle, nephron structure, ultrafiltration, selective reabsorption, the loop of Henle, ADH and osmoregulation, kidney failure, dialysis and transplants, and urine tests.
• 5.1.3 Sensory receptors as transducers, neurone structure, resting and action potentials, saltatory conduction, and cholinergic synapses with summation.
• 5.1.4 The endocrine system, adrenal glands, the pancreas and islets of Langerhans, insulin secretion by beta cells, control of blood glucose, and type 1 and type 2 diabetes.
• 5.1.5 Plant responses and hormones (auxin, gibberellin, abscisic acid), the brain, reflexes, coordination of heart rate, the fight or flight response and muscle structure and contraction.
• 5.2.1 and 5.2.2 Light-dependent and light-independent reactions, limiting factors, glycolysis, the link reaction, Krebs cycle, oxidative phosphorylation and chemiosmosis, anaerobic respiration and RQ values for different respiratory substrates.

Common mistakes in Module 5: Communication, Homeostasis and Energy

• Saying insulin converts glucose to glycogen. Insulin binds to receptors and triggers responses such as more glucose transporters and activation of enzymes for glycogenesis; it does not react with glucose itself.
• Confusing glycogenesis, glycogenolysis and gluconeogenesis. Glycogenesis makes glycogen; glycogenolysis breaks it down; gluconeogenesis makes glucose from non-carbohydrates.
• Stating that the ornithine cycle makes ammonia. Deamination produces ammonia, and the ornithine cycle converts it with carbon dioxide into less toxic urea.
• Writing that the H band lengthens during contraction. The I band and H zone shorten while the A band stays the same length.
• Saying oxygen is used in the Krebs cycle. Oxygen is only used as the final electron acceptor in oxidative phosphorylation.

Try three Module 5: Communication, Homeostasis and Energy exam-style questions