AQA GCSE Biology Exam Questions

• Any two from: cell wall, chloroplasts, permanent vacuole (1 mark each).

• Real size = image size ÷ magnification = 24 ÷ 400 = 0.06 mm (1 mark).
• 0.06 mm × 1000 = 60 µm (1 mark).

Tip: Convert units at the end: 1 mm = 1000 µm.

• Water moved out of the potato cells by osmosis (1 mark).
• From a dilute solution (in the cells) to a more concentrated solution (outside) (1 mark).
• Across a partially permeable membrane (1 mark).

• By active transport (1 mark).
• Against a concentration gradient, from dilute soil water to more concentrated cell sap (1 mark).
• Using energy from respiration (1 mark).

• Benefit: can differentiate into many cell types, so could replace damaged nerve cells (1 mark).
• Concern: ethical objections to using embryos, or risk of infection or rejection (1 mark).
• Justified conclusion weighing these points (1 mark).

• Substrate: lipids (fats) (1 mark).
• Products: fatty acids and glycerol (1 mark).

• The enzyme becomes denatured (1 mark).
• The shape of the active site changes (1 mark).
• The substrate no longer fits the active site, so fewer enzyme-substrate complexes form (1 mark).

• 1000 ÷ 50 = 20 s⁻¹ (1 mark).

• Vena cava into the right atrium, then right ventricle (1 mark).
• Pulmonary artery to the lungs, returning in the pulmonary vein (1 mark).
• Into the left atrium, then left ventricle (1 mark).
• Out through the aorta, with valves preventing backflow (1 mark).

• Large surface area (1 mark).
• Thin walls, one cell thick, giving a short diffusion distance (1 mark).
• Good blood supply maintains a steep concentration gradient (1 mark).

• Inhaling droplets from sneezes or coughs (1 mark).
• Close contact with an infected person (1 mark).

• Antibiotics kill bacteria, not viruses (1 mark).
• Viruses live and reproduce inside cells, so drugs that destroy them may damage body tissue (1 mark).

• A small quantity of dead or inactive pathogen is introduced (1 mark).
• White blood cells produce antibodies specific to its antigens (1 mark).
• Memory of the pathogen remains (1 mark).
• If the live pathogen enters, antibodies are produced quickly, preventing illness (1 mark).

• Any two from: phagocytosis, producing antibodies, producing antitoxins (1 mark each).

• Low doses on healthy volunteers first check for safety and side effects (1 mark).
• Patients then help find the optimum dose and efficacy (1 mark).
• In a double blind trial neither doctors nor patients know who gets the placebo, which removes bias (1 mark).

• Carbon dioxide + water (1 mark) → glucose + oxygen (1 mark), with light energy.

• Light intensity ∝ 1 ÷ distance² (1 mark).
• (20 ÷ 10)² = 4, so the intensity is 4 times lower (1 mark).

• Another factor becomes limiting (1 mark).
• Such as carbon dioxide concentration or temperature (1 mark).

• Aerobic uses oxygen; anaerobic does not (1 mark).
• Aerobic produces carbon dioxide and water; anaerobic produces lactic acid (1 mark).
• Aerobic transfers much more energy per glucose molecule (1 mark).

• Lactic acid built up from anaerobic respiration, creating an oxygen debt (1 mark).
• Extra oxygen is needed to react with the lactic acid (1 mark).
• Blood carries lactic acid to the liver, where it is converted back to glucose (1 mark).

• Receptor in the skin detects the stimulus (1 mark).
• Impulse travels along a sensory neurone (1 mark).
• Through a relay neurone in the spinal cord (1 mark).
• Along a motor neurone to an effector (muscle), which contracts (1 mark).

• The pancreas detects the rise and releases insulin (1 mark).
• Insulin causes glucose to move from the blood into cells (1 mark).
• In the liver and muscles excess glucose is converted to glycogen for storage (1 mark).

• Nervous responses are faster; hormonal are slower (1 mark).
• Nervous effects are short-lived and localised; hormonal effects last longer and can be widespread (1 mark).

• FSH causes an egg to mature in the ovary (1 mark).
• LH stimulates the release of the egg (ovulation) (1 mark).

• Control variables, any two: same hand, same starting position of the ruler, same person dropping it, no warning (1 mark each).
• Repeat the test several times and calculate a mean (1 mark).

• Meiosis produces four cells; mitosis produces two (1 mark).
• Meiosis produces genetically different cells with half the chromosome number; mitosis produces identical cells (1 mark).

• Correct gametes: F and f from each parent (1 mark).
• Offspring genotypes FF, Ff, Ff, ff (1 mark).
• Probability 1 in 4, 0.25 or 25% (1 mark).

• Homozygous: two identical alleles of a gene (1 mark).
• Phenotype: the characteristic that is expressed or seen (1 mark).

• A random mutation makes some bacteria resistant (1 mark).
• The antibiotic kills non-resistant bacteria (1 mark).
• Resistant bacteria survive and reproduce (1 mark).
• The resistance allele is passed on, so the resistant population grows (1 mark).

• Choose parents with the highest milk yield (1 mark).
• Breed them together (1 mark).
• Select the best offspring and repeat over many generations (1 mark).

• Total area sampled = 10 × 0.25 = 2.5 m² (1 mark).
• Mean density = 30 ÷ 2.5 = 12 daisies per m² (1 mark).
• Population = 12 × 200 = 2400 daisies (1 mark).

• Not all material is eaten, such as bones or roots (1 mark).
• Some is lost as waste, faeces and urine (1 mark).
• Much glucose is used in respiration and released as carbon dioxide (1 mark).

• Respiration by plants and animals (1 mark).
• Decay by microorganisms (decomposers) respiring (1 mark).
• Combustion of fuels (1 mark).

• Any two from: light intensity, temperature, moisture, soil pH and mineral content, wind, carbon dioxide (1 mark each).

• Habitats are destroyed (1 mark).
• Species lose food and shelter, so populations fall or become extinct (1 mark).
• Loss of one species affects others in the food web (1 mark).