Respiration and ATP

IGCSE Edexcel Biology
2.34–2.38 Respiration and ATP
Key Concept: Respiration releases energy to make ATP. Aerobic respiration uses oxygen and produces carbon dioxide and water. Anaerobic respiration occurs without oxygen and produces different products in plants and animals.

Section A: ATP and Aerobic Respiration

1. What is ATP and why is it important in cells? [3]
2. Write the word equation and balanced symbol equation for aerobic respiration. [4]

Section B: Anaerobic Respiration

3. State the word equation for anaerobic respiration in animals. [2]
4. State the word equation for anaerobic respiration in plants/yeast. [3]
5. Compare aerobic and anaerobic respiration. [4]

Section C: Practical and Application

6. Describe one observation that shows carbon dioxide is produced by respiring seeds. [2]
7. Give two uses of energy from respiration in cells. [2]
Total marks: 20

Mark Scheme

1. ATP is the energy-carrying molecule in cells [1]; provides energy for cellular processes [1]; produced during respiration [1]
2. Word: glucose + oxygen → carbon dioxide + water (+ energy/ATP) [2]; Symbol: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O [2]
3. Glucose → lactic acid (+ energy) [2]
4. Glucose → ethanol + carbon dioxide (+ energy) [3]
5. Any four: aerobic uses oxygen; anaerobic does not; aerobic produces CO₂ + water, anaerobic produces lactic acid (animals) or ethanol + CO₂ (plants/yeast); aerobic releases more energy; both break down glucose [4]
6. Limewater turns milky/cloudy or hydrogen carbonate indicator changes colour (any valid observation) [2]
7. Any two: active transport, muscle contraction, protein synthesis, cell division, maintaining temperature [2]