OCR A Level Biology B Module 2: Cells, Chemicals for Life, Transport and Gas Exchange Exam Questions

About OCR A Level Biology B Module 2: Cells, Chemicals for Life, Transport and Gas Exchange

Module 2 of OCR A Level Biology B (Advancing Biology) brings together the chemistry of life and the systems that move materials around organisms. It covers microscopy and cells, the properties of water, protein structure and enzymes, nucleic acids, the heart, blood vessels and blood, gas exchange in mammals and plants, and transport in plants. True to the context-led Advancing Biology approach, ideas are often set in health or real-world scenarios. Examiners expect structure and function links, interpretation of ECGs and pressure graphs, enzyme kinetics, water potential reasoning and calculations such as magnification and cardiac output.

What you need to know

• 2.1.1 Light and electron microscopy, magnification and resolution, staining and calibration with a graticule, and the ultrastructure of eukaryotic and prokaryotic cells.
• 2.1.2 Hydrogen bonding in water and how it gives cohesion, high specific heat capacity, solvent properties and density changes, and why these matter to organisms.
• 2.1.3 Amino acids, peptide bonds and the levels of protein structure, globular and fibrous proteins, enzyme mechanism, factors affecting rate, and inhibition.
• 2.1.4 Nucleotide structure, DNA and RNA, semi-conservative replication and the role of DNA in protein synthesis.
• 2.2.1 and 2.2.2 Heart structure, the cardiac cycle and its control, ECG traces, blood vessels, tissue fluid, haemoglobin and the oxygen dissociation curve, and cardiovascular disease risk factors.
• 2.2.3 and 2.2.4 Ventilation and alveoli in mammals, lung volumes, gas exchange in leaves through stomata, and water and sucrose transport in xylem and phloem.

Common mistakes in Module 2: Cells, Chemicals for Life, Transport and Gas Exchange

• Saying water has a high specific heat capacity because its molecules are heavy. It is because many hydrogen bonds must be broken to raise the temperature.
• Describing an enzyme's active site as rigid in all cases. The induced fit model says the active site changes shape slightly as the substrate binds.
• Mislabelling an ECG. The P wave is atrial depolarisation, the QRS complex is ventricular depolarisation and the T wave is ventricular repolarisation.
• Saying veins have thick muscular walls. Arteries have thick muscle and elastic tissue; veins have thin walls, a wide lumen and valves.
• Saying stomata close at night only to save water. Stomata respond to light, carbon dioxide and water availability; closure reduces water loss but also limits gas exchange.

Try three Module 2: Cells, Chemicals for Life, Transport and Gas Exchange exam-style questions