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S4 Biology: Cellular Respiration Paper 3 (Challenge)
S4 Biology: Cellular Respiration Paper 3 (Challenge)
The final paper is data and explanation heavy: oxygen debt, NAD, mole conversions and what an RQ above 1 means.
Quick answer 1. stepwise at body temperature | 2. oxidise lactate | 3. endurance rises | 4. carries hydrogen to the chain | 5. 0.6 cm3 per minute | 6. 12 cm3 | 7. +150% | 8. 0.015 mol, 360 cm3 | 9. RQ 1.1, another carbon source | 10. only pure carbohydrate gives 1
01 Paper details (check answers afterwards)
| Item | Detail |
|---|---|
| Questions | 10 questions |
| Suggested time | 25 minutes |
| Difficulty mix | Foundation 4 · Intermediate 3 · Challenge 2 · Error redo 1 |
| Chapter | Chapter: S4 Biology — Cellular Respiration |
| Level | Challenge |
02 Questions (10 items)
- FoundationIn terms of energy release, how does respiration differ from burning?
- FoundationWhy does deep breathing continue for a while after hard exercise (oxygen debt)?
- FoundationWhat effect does a higher mitochondrial count have on muscular endurance?
- FoundationWhat is the main role of NAD in respiration?
- IntermediateYeast in a test tube produces 18 cm3 of carbon dioxide in 30 minutes. What is the average per minute?
- Intermediate100 g of tissue uses 240 cm3 of oxygen per hour. How much does 10 g use in 30 minutes?
- IntermediateA fish uses 20 cm3 of oxygen per hour at 10 C and 50 cm3 at 25 C. By what percentage does uptake rise?
- Challenge0.45 g of glucose (Mr 180) is fully oxidised. How many moles of oxygen are needed, and what volume in cm3 at 24.0 dm3/mol?
- ChallengeAn organism releases 264 cm3 of carbon dioxide and takes up 240 cm3 of oxygen in 2 hours. What is the RQ and how do you explain a value above 1?
- Error redoA student says the respiratory quotient is always 1. What is wrong?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | Respiration releases energy step by step at body temperature under enzyme control; burning releases it at once at high temperature. | Stepwise release lets the cell capture energy gradually. |
| 2 | Extra oxygen is needed to oxidise the accumulated lactate. | The oxygen debt is the oxygen still owed after exercise. |
| 3 | Endurance improves because aerobic capacity rises. | Training multiplies mitochondria, the cellular basis of endurance. |
| 4 | It carries hydrogen (electrons) to the electron transport chain. | NAD is a hydrogen carrier that is reduced and then reused. |
| 5 | About 0.6 cm3 per minute. | Rate = volume divided by time. |
| 6 | 12.0 cm3. | Find the per-gram hourly rate, then scale by mass and time. |
| 7 | It rises by 150.0%. | Rise = (50 – 20) / 20 x 100. |
| 8 | It needs 0.015 mol of oxygen, that is 360 cm3. | That is 0.0025 mol of glucose, each needing six moles of oxygen. |
| 9 | RQ = 1.1; above 1 means some carbon dioxide comes from anaerobic routes or organic acid metabolism. | Pure carbohydrate gives exactly 1.0, so a value above 1 needs another carbon source. |
| 10 | Only carbohydrate approaches 1; fat is about 0.7 and protein about 0.8. | RQ depends on the carbon, hydrogen and oxygen ratio of the substrate. |
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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