Question 1
Paper 1A style
Which statement about ATP is correct?
- It is a nucleotide containing deoxyribose.
- Energy is required to hydrolyse it to ADP and phosphate.
- It is a nucleotide, and its hydrolysis to ADP and phosphate releases energy.
- It moves freely out of cells through the plasma membrane.
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Answer: C [1]
Question 2
Paper 1A style
Which feature is shared by aerobic and anaerobic cell respiration in humans?
- Both produce carbon dioxide.
- Both require mitochondria.
- Both can use glucose as the substrate.
- Both produce lactate.
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Answer: C [1]
Question 3
Paper 1B style
A respirometer containing 3.0 g of maggots and soda lime was kept at three temperatures. The distance moved by the liquid drop in 5 minutes was recorded. The capillary tube has a cross-sectional area of 0.80 mm². The data are for practice. (a) Calculate the rate of oxygen uptake per gram at 25 °C, in mm³ g⁻¹ min⁻¹. Show your working. [2] (b) Identify the independent and the dependent variable. [1] (c) Explain the trend shown in the data. [2]
| Temperature / °C | Mean distance moved / mm |
|---|---|
| 15 | 11 |
| 20 | 17 |
| 25 | 24 |
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- (a) volume = 0.80 × 24 = 19.2 mm³ [1]
- (a) 19.2 ÷ 5 ÷ 3.0 = 1.28 mm³ g⁻¹ min⁻¹ / 1.3 [1]
- (b) independent: temperature; dependent: distance moved by drop / rate of oxygen uptake (both needed) [1]
- (c) rate of oxygen uptake / respiration increases with temperature [1]
- (c) respiration is catalysed by enzymes; more kinetic energy so more frequent substrate–active site collisions [1]
- (c) (temperatures are below the optimum so) no denaturation [1]
- (c) [max 2]
Question 4
Paper 2A style
(a) State two processes in cells that use energy from ATP. [2] (b) Distinguish between cell respiration and gas exchange. [1]
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- (a) active transport across membranes [1]
- (a) synthesis of macromolecules / anabolism [1]
- (a) movement of the whole cell (e.g. muscle contraction, flagella) / movement of chromosomes [1]
- (a) [max 2]
- (b) cell respiration produces ATP from carbon compounds inside cells, whereas gas exchange is diffusion of O₂ and CO₂ between organism and environment OWTTE [1]