Edexcel International GCSE Biology 4BI1: Respiration – Practice Questions

These are original questions written for Marlbridge, for revision and practice on this content. They are not reproduced past-paper questions, and they do not replicate the exam’s exact structure, question count or mark tariffs – examination boards hold copyright in their own papers. Use these alongside the official past papers from your board or school.

These questions cover sub-topic 2(f), Respiration (points 2.34–2.39), of the Pearson Edexcel International GCSE Biology (4BI1) specification, Issue 3, for the November and June series examined under Issue 3. The course is untiered and a calculator may be used on both papers. None of these points is a bold B statement, so every question here could appear on Paper 1 or Paper 2.

Learn the content first in the study guide and the revision notes. For questions on mitochondria and other organelles, use the cell structure practice questions. The course hub is Edexcel IGCSE Biology and the printable checklist lists every point.

Questions

1. Complete the balanced symbol equation for aerobic respiration.

C₆H₁₂O₆ + …….. → …….. + 6H₂O [2]

2. A student writes this equation for aerobic respiration:

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 12H₂O

Explain why the equation is not balanced and write the correct version. [3]

3. Muscle cells contain many mitochondria.

(a) State two processes, other than muscle contraction, that use energy from ATP in cells. [2] (b) Explain why muscle cells contain many mitochondria. [2]

4. After heavy rain, a field becomes waterlogged and the soil spaces fill with water.

(a) Explain why the root cells of the crop start to respire anaerobically. [2] (b) Give the word equation for anaerobic respiration in the root cells. [2] (c) Suggest why the roots take up fewer mineral ions while the soil is waterlogged. [2]

5. A student sets up three vacuum flasks of germinating peas and three of boiled peas. All six flasks start at 20.0 °C. The table shows the temperatures after 2 days.

Flask	Germinating peas / °C	Boiled peas / °C
1	24.3	20.1
2	24.9	20.3
3	24.6	20.2

(a) Calculate the mean final temperature of the germinating peas. [2] (calculator allowed) (b) Calculate the mean rate of temperature rise of the germinating peas, in °C per day. [2] (c) Explain why both batches of peas were rinsed in disinfectant before being put in the flasks. [2] (d) Explain why the temperature of the germinating peas rose. [2]

6. A student places 5 woodlice in tube P and 10 woodlice in tube Q. Each tube contains 10 cm³ of hydrogen-carbonate indicator below a gauze platform. Both tubes are sealed and kept at 20 °C.

(a) State the colour change the student would see. [1] (b) Predict which tube changes colour first. Explain your prediction. [2] (c) Give two variables, other than temperature and volume of indicator, that should be kept the same. [2] (d) Suggest why the woodlice are kept on a gauze platform. [1]

7. During a 200 m sprint, an athlete’s leg muscles respire anaerobically.

(a) Explain why the leg muscles respire anaerobically during the sprint. [2] (b) Explain why anaerobic respiration releases less energy from each glucose molecule than aerobic respiration. [2]

8. Yeast is grown in two flasks of sugar solution at 30 °C. Air is bubbled through flask X. Flask Y is sealed so no air can enter.

(a) Name the gas produced by the yeast in both flasks. [1] (b) Name one substance produced in flask Y but not in flask X. [1] (c) Explain why the yeast population grows faster in flask X. [2]

9. A carbon dioxide sensor is used to measure the volume of carbon dioxide released by 20 g of germinating seeds. At 25 °C, the seeds release 6.0 cm³ of carbon dioxide in 15 minutes. (calculator allowed)

(a) Calculate the rate of carbon dioxide release in cm³ per minute. [2] (b) Calculate the rate of carbon dioxide release per gram of seeds, in cm³ per gram per minute. [1] (c) The experiment is repeated at 15 °C. The seeds release 3.6 cm³ of carbon dioxide in 15 minutes. Calculate the percentage decrease in the rate compared with 25 °C. [3] (d) Explain why the rate is lower at 15 °C. [2]

10. Compare aerobic respiration in a leaf cell with anaerobic respiration in a yeast cell. [4]

11. Describe how you could investigate the effect of temperature on the rate of respiration of germinating seeds, using hydrogen-carbonate indicator. [6]

Answers

1. 6O₂ (on the left) [1]; 6CO₂ (on the right) [1] [2] Examiner insight: Each formula needs the correct number in front; “O₂” without the 6 or “CO₂” without the 6 does not score, and “6O” is not accepted for oxygen.

2. There are 24 hydrogen atoms on the right but only 12 on the left [1]; there are 24 oxygen atoms on the right but only 18 on the left [1]; correct equation: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O [1] [3] Examiner insight: “It doesn’t add up” is too vague for credit; the marks need a named element with the atom counts on each side.

3. (a) Any two: active transport [1]; building large molecules such as proteins [1]; cell division / growth; nerve impulses (b) Muscle cells need a lot of energy for contraction [1]; more mitochondria means more aerobic respiration, so more ATP / energy is released [1] Examiner insight: An answer saying mitochondria “make energy” loses the second mark in (b); write “release energy” or “produce ATP”.

4. (a) Water fills the air spaces, so little oxygen reaches the roots [1]; without enough oxygen, aerobic respiration cannot happen [1] (b) glucose → [1] ethanol + carbon dioxide [1] (c) Anaerobic respiration releases less energy / makes less ATP [1]; mineral ions are taken up by active transport, which needs energy [1] Examiner insight: In (b), lactic acid as the product scores zero for the products mark because it is the animal equation; both ethanol and carbon dioxide are needed.

5. (a) (24.3 + 24.9 + 24.6) ÷ 3 [1] = 24.6 °C [1] (b) Rise = 24.6 − 20.0 = 4.6 °C [1]; rate = 4.6 ÷ 2 = 2.3 °C per day [1] (c) To kill microorganisms on the peas [1]; so that the microorganisms do not respire and release heat, and any temperature rise is due to the peas only [1] (d) The germinating peas respire and release energy as heat [1]; the vacuum flask insulates them, so the heat is not lost [1] Examiner insight: In (b), an error carried forward from (a) is allowed: a wrong mean used correctly still earns the rate mark.

6. (a) From red (orange) to yellow [1] (b) Tube Q, because more woodlice respire [1]; so carbon dioxide is released faster [1] (c) Any two: size / mass of woodlice [1]; type / species of woodlice [1]; size of tube; time the tubes are left (d) So the woodlice do not touch / contaminate the indicator (and are not harmed by it) [1] Examiner insight: For (a) both colours are needed for the mark; “turns yellow” alone does not show a change.

7. (a) Muscles need energy faster than oxygen can be supplied by the blood [1]; so some glucose is broken down without oxygen [1] (b) Glucose is only partly broken down [1]; much of the energy remains in the lactic acid [1] Examiner insight: “No oxygen” on its own in (a) is not enough; the mark is for oxygen supply being too slow for the demand.

8. (a) Carbon dioxide [1] (b) Ethanol [1] (c) Yeast in X respires aerobically [1]; this releases more energy / ATP for growth and reproduction [1] Examiner insight: In (c), “more respiration” earns nothing unless you say it is aerobic and that it releases more energy.

9. (a) 6.0 ÷ 15 [1] = 0.40 cm³ per minute [1] (b) 0.40 ÷ 20 = 0.02 cm³ per gram per minute [1] (c) Rate at 15 °C = 3.6 ÷ 15 = 0.24 cm³ per minute [1]; (0.40 − 0.24) ÷ 0.40 × 100 [1] = 40% [1] (d) Respiration is controlled by enzymes [1]; at a lower temperature the enzymes and substrate molecules move more slowly, so fewer successful collisions happen per minute [1] Examiner insight: Saying the enzymes are “denatured” at 15 °C is wrong and cancels a mark in (d); low temperature slows enzymes but does not denature them.

10. Any four: aerobic needs oxygen, anaerobic does not [1]; aerobic produces carbon dioxide and water, anaerobic produces ethanol and carbon dioxide [1]; aerobic releases more energy / ATP per glucose [1]; aerobic breaks glucose down completely, anaerobic only partly [1]; aerobic happens mainly in mitochondria, anaerobic in the cytoplasm; both produce carbon dioxide / both release energy / both use glucose [4] Examiner insight: A “compare” answer must link both processes in each point; four facts about aerobic respiration alone do not show a comparison and score no marks.

11. Any six:

• Put the same volume of hydrogen-carbonate indicator in a set of boiling tubes [1]
• Place the same mass of germinating seeds of the same type on a gauze platform above the indicator in each tube [1]
• Seal each tube with a bung [1]
• Put the tubes in water baths at a range of temperatures, e.g. 10, 20, 30 and 40 °C [1]
• Time how long the indicator takes to change from red to yellow [1]
• Set up a control at each temperature with boiled (dead) seeds or glass beads [1]
• Keep the tubes in the dark so photosynthesis does not affect the result; repeat and calculate a mean time [6] Examiner insight: Each mark needs a separate, practical step; “keep everything fair” earns nothing unless the controlled variables are named.

Where marks are usually lost

• Writing “respiration produces energy” instead of “releases energy” or “produces ATP”.
• Giving lactic acid for plants or yeast, or ethanol for animals.
• Leaving carbon dioxide out of the plant/yeast anaerobic equation.
• Missing the 6 in front of O₂ or CO₂ in the symbol equation.
• Colour changes stated without the starting colour.
• Not explaining why boiled seeds act as a control (dead cells do not respire).
• Rates without units, or the wrong time unit.
• Saying low temperature “denatures” enzymes.
• Comparison answers that only describe one type of respiration.

Next steps

• Recap with the revision notes.
• Reread any weak section in the study guide.
• Browse other topics on the Edexcel IGCSE Biology hub.
• Track coverage with the printable checklist.
• Try all free 10-minute diagnostics.
• Book a free trial class.

Official syllabus

Pearson Edexcel International GCSE in Biology (4BI1) specification, Issue 3, first examination June 2019, Pearson Education Limited – Section 2, Structure and functions in living organisms, sub-topic (f) Respiration, points 2.34–2.39.