AQA GCSE FOUNDATION Biology: Aerobic and Anaerobic Respiration

AQA GCSE Foundation Biology: Aerobic and Anaerobic Respiration

Introduction

All living organisms need energy to survive. This energy comes from the breakdown of food molecules, a process called respiration. There are two main types of respiration: aerobic and anaerobic.

Aerobic Respiration

• Definition: Aerobic respiration is the process of breaking down glucose using oxygen to release energy.
• Equation: Glucose + Oxygen ? Carbon dioxide + Water + Energy C6H12O6 + 6O2 ? 6CO2 + 6H2O + Energy
• Stages: Aerobic respiration takes place in three main stages:
  1. Glycolysis: This occurs in the cytoplasm and involves the breakdown of glucose into pyruvate. A small amount of energy is released in this stage.
  2. Krebs Cycle: This occurs in the mitochondria and involves the further breakdown of pyruvate, releasing more energy.
  3. Electron Transport Chain: This is also in the mitochondria and involves the final breakdown of pyruvate, releasing the most energy.
• Energy Yield: Aerobic respiration is highly efficient and produces a large amount of energy (approximately 38 ATP molecules per glucose molecule).

Anaerobic Respiration

• Definition: Anaerobic respiration is the process of breaking down glucose without using oxygen to release energy. This is also known as fermentation.
• Equation: Glucose ? Lactic acid + Energy (in animals) Glucose ? Ethanol + Carbon dioxide + Energy (in plants and yeast)
• Stages: Anaerobic respiration involves only glycolysis, which is less efficient than aerobic respiration.
• Energy Yield: Anaerobic respiration produces much less energy (approximately 2 ATP molecules per glucose molecule).
• Products: Anaerobic respiration produces different products depending on the organism:
  • Animals: Lactic acid is produced.
  • Plants and yeast: Ethanol and carbon dioxide are produced.

Comparing Aerobic and Anaerobic Respiration

Importance of Respiration

Respiration is vital for all living organisms because it provides the energy needed for essential life processes such as:

• Movement: Muscle contraction requires energy.
• Growth and repair: Building new cells and tissues requires energy.
• Active transport: Moving substances across cell membranes requires energy.
• Maintaining body temperature: Warm-blooded animals need energy to regulate their body temperature.

Summary

• Aerobic respiration uses oxygen to break down glucose, releasing a large amount of energy.
• Anaerobic respiration does not use oxygen, producing less energy and different byproducts.
• Both types of respiration are essential for life, providing energy for various biological processes.

Key Terms

• Respiration: The process of breaking down food molecules to release energy.
• Aerobic: Requiring oxygen.
• Anaerobic: Not requiring oxygen.
• Glucose: A simple sugar used as a fuel source in respiration.
• ATP: Adenosine triphosphate, the energy currency of cells.
• Lactic acid: A byproduct of anaerobic respiration in animals.
• Ethanol: A byproduct of anaerobic respiration in plants and yeast.
• Mitochondria: The organelle where aerobic respiration takes place.

Practice Questions

1. Explain the difference between aerobic and anaerobic respiration.
2. What are the products of anaerobic respiration in animals?
3. Why is aerobic respiration more efficient than anaerobic respiration?
4. Give two examples of how organisms use the energy released by respiration.
5. What are the advantages and disadvantages of anaerobic respiration?