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S5 Biology: Respiration (Paper 4)
S5 Biology: Respiration (Paper 4)
The fourth paper mixes the three stages, energy calculations, fuel comparison and experimental design.
Direct answer Separate the site and products of each stage; multiply a per-minute rate by time for energy; a quotient of 1.0 means carbohydrate and 0.7 means fat; four ATP come from substrate-level phosphorylation.
01 Paper details (check answers afterwards)
| Item | Detail |
|---|---|
| Questions | 10 |
| Suggested time | 25 |
| Difficulty mix | Foundation 4 · Intermediate 3 · Challenge 2 · Error redo 1 |
| Chapter | Chapter: S5 Biology: Respiration |
| Level | Four basic, three advanced, two challenge and one error-repair item |
02 Questions (10 items)
- FoundationWhere do the three main stages of aerobic respiration take place?
- FoundationWhen the electron transport chain runs, what do oxygen and hydrogen ions form?
- FoundationCompared with burning, what is special about biological oxidation?
- FoundationAn athlete uses 3 dm³ of oxygen a minute and each dm³ releases about 20 kJ. How much energy is released in ten minutes?
- IntermediateA person’s respiratory quotient rises from 0.85 to 1.0 during hard exercise. What does this show about the fuel?
- IntermediateYeast uses 0.5 g of glucose a minute without oxygen. About how much ethanol is produced?
- IntermediateAt noon on a hot day stomata close and the photosynthetic rate falls despite strong sunlight. Why?
- ChallengeOf the 30 ATP from one glucose, how many come from substrate-level phosphorylation in glycolysis and the Krebs cycle?
- ChallengeHow would you show experimentally that germinating seeds are respiring aerobically?
- Error redoA student says all ATP in aerobic respiration comes from the electron transport chain. What is wrong?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | Glycolysis in the cytoplasm, the Krebs cycle in the mitochondrial matrix, and the electron transport chain on the inner membrane | The three stages sit in different places: cytoplasm, matrix and inner membrane. |
| 2 | Water | Oxygen is the final electron acceptor, so without it the chain stops and water is not formed. |
| 3 | It happens at body temperature in many enzyme-controlled steps, storing energy in ATP | Burning releases heat in one burst, while biological oxidation releases energy in small enzyme-controlled steps. |
| 4 | 600 kJ | Three times twenty gives 60 kJ per minute, and ten minutes gives 600 kJ. |
| 5 | The fuel shifts from a mixture of fat and carbohydrate to mainly carbohydrate | A quotient near 1.0 means carbohydrate is the main fuel, while 0.7 points to fat. |
| 6 | About 0.26 g | 180 g of glucose gives 92 g of ethanol, so half a gram gives about 0.26 g. |
| 7 | Less carbon dioxide enters, so carbon dioxide becomes the limiting factor | Keeping water in costs the plant its carbon dioxide supply when stomata close. |
| 8 | Four: two from glycolysis and two from the Krebs cycle | The rest, about 26, comes from oxidative phosphorylation. |
| 9 | Seal them with sodium hydroxide to absorb carbon dioxide, then watch the gas volume or a dye drop move | Removing carbon dioxide lets any fall in gas volume show oxygen being used. |
| 10 | Glycolysis and the Krebs cycle each make ATP directly, four in total; the chain supplies only the remaining 26 | Crediting all 30 ATP to the chain ignores the four made directly in the earlier stages. |
04 What to do after marking
- After marking, redo only the wrong items and write down which step went wrong (formula, unit, or misread number).
- Repeat the same item two days later; move to the next paper only when both attempts are correct.
- Parents only need the answer and note columns; there is no need to explain every item.
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