Biology practice questions

Biology practice questions Set 1: Q1 (Cell Biology) — Fig 1 shows a plant cell and an animal cell. State two structural differences between a plant cell and an animal cell, other than the presence of chloroplasts. [2] Q2 (Movement of Substances) A student places a potato strip into a concentrated salt solution. (a) Name the process by which water moves out of the potato cells. [1] (b) Explain, in terms of water potential, why water moves out of the cells. [3] Q3 (Nutrition — Enzymes) An experiment tested the effect of pH on the activity of amylase, using the iodine test to monitor starch breakdown at 2-minute intervals. (a) Describe how the iodine test is used to show that starch has been broken down. [2] (b) Sketch and describe the shape of a graph of enzyme activity against pH for a typical human enzyme. [3] Q4 (Transport in Humans) (a) State two differences between arteries and veins. [2] (b) Explain why the left ventricle has a thicker muscular wall than the right ventricle. [2] Q5 (Respiration) (a) Write the word equation for anaerobic respiration in muscle cells. [1] (b) Explain why muscle cells respire anaerobically during vigorous exercise. [2] Q6 (Molecular Genetics) (a) Describe the process of transcription. [3] (b) Explain how a mutation in the base sequence of DNA could result in a non-functional protein. [3] Q7 (Homeostasis) Explain how the body responds to a rise in blood glucose concentration after a meal, including the role of insulin. [4]

Q8 (Reproduction) State two functions of amniotic fluid during pregnancy. [2] Set 2: Q1 (Molecular Genetics) (a) State the base pairing rule in DNA. [1] (b) A gene has the DNA template strand base sequence: TAC GGA CTT. State the mRNA sequence produced from this template. [2] Q2 (Genetic Engineering) Describe how a human gene (e.g. the insulin gene) can be inserted into a bacterium to produce a genetically modified organism. [4] Q3 (Enzymes) A student investigated the effect of temperature on the rate of an enzyme-catalysed reaction. (a) Describe how the rate of reaction changes as temperature increases from 10°C to 80°C. [3] (b) Explain, in terms of enzyme structure, why the rate of reaction decreases sharply above the optimum temperature. [3] Q4 (Photosynthesis) (a) Write the word equation for photosynthesis. [1] (b) A plant is placed in a beaker of water containing sodium hydrogencarbonate under a lamp. Explain why the number of bubbles produced increases as the lamp is moved closer to the plant. [3] Q5 (Respiratory System) (a) State two features of alveoli that adapt them for efficient gas exchange. [2] (b) Explain why smoking can lead to a decrease in the efficiency of gas exchange. [3] Q6 (Excretion) (a) Name the structure in the kidney responsible for ultrafiltration. [1] (b) Explain why glucose is normally completely reabsorbed in the kidney tubule, but is present in the urine of a person with untreated diabetes. [3]

Q7 (Coordination — Nervous System) Describe the pathway of a reflex arc when a person accidentally touches a hot object, from stimulus to response. [4] Q8 (Reproduction — Hormones) State the roles of oestrogen and progesterone in the menstrual cycle. [3] Set 3: Q1 (Excretion) Explain why urea, but not glucose, is normally found in urine. [3] Q2 (Classification) State three features used to classify an organism as belonging to the phylum Arthropoda. [3] Q3 (Nutrition — Digestion) (a) Name the enzyme that digests protein in the stomach, and state the substrate and products of this reaction. [3] (b) Explain why pepsin requires an acidic environment to function effectively, and name the structure that produces this acid. [2] Q4 (Transport in Plants) (a) Define transpiration. [1] (b) Explain how a decrease in humidity would affect the rate of transpiration. [2] Q5 (Homeostasis — Temperature Regulation) Explain how the body responds when core body temperature rises above normal, with reference to sweat glands and blood vessels in the skin. [4] Q6 (Ecology) (a) Define the term "food chain." [1] (b) Explain why there are usually no more than 4–5 trophic levels in a food chain. [2] Q7 (Molecular Genetics — Cell Division) (a) State one difference between mitosis and meiosis in terms of the number of daughter cells produced. [1]

(b) Explain why meiosis, but not mitosis, is important for genetic variation. [3] Q8 (Respiration) Compare aerobic and anaerobic respiration in terms of the amount of energy released. [2] Answers: Set 1 Q1 (Cell Biology) — Two differences between plant and animal cells (other than chloroplasts): ● Plant cells have a cell wall (made of cellulose); animal cells do not. ● Plant cells have one large, permanent central vacuole ; animal cells have small/temporary vacuoles (if any). Q2 (Movement of Substances) (a) Osmosis . (b) The salt solution has a lower (more negative) water potential than the cell sap inside the potato cells. Water moves from a region of higher water potential (inside the cell) to a region of lower water potential (the salt solution), through the partially permeable cell membrane . Q3 (Enzymes — Amylase) (a) Add iodine solution to the sample at intervals. If starch is present, the iodine turns from orange-brown to blue-black . As starch is broken down, the colour change becomes less intense/eventually stays orange-brown, showing starch has disappeared. (b) Enzyme activity is low at low pH , rises to a peak at the optimum pH (~pH 7 for most human enzymes), then falls sharply past the optimum. The curve is roughly bell-shaped — extreme pH denatures the enzyme, changing the shape of its active site. Q4 (Transport in Humans) (a) Arteries have thick, muscular, elastic walls and a narrow lumen ; veins have thinner walls , a wider lumen , and contain valves (arteries do not). (b) The left ventricle pumps blood to the whole body (a longer distance, against higher resistance), so it needs higher pressure , requiring a

thicker muscular wall . The right ventricle only pumps blood to the nearby lungs , needing less pressure. Q5 (Respiration) (a) Glucose → lactic acid. (b) During vigor