22. Aerobic and Anaerobic Respiration

Respiration is an exothermic reaction that transfers energy from glucose. It occurs continuously in all living cells to provide the energy required for various biological processes.

1. Why Do Organisms Need Energy?

Energy from respiration is used for many essential functions, including:

• Building Molecules: Combining smaller molecules to create larger ones (e.g., amino acids forming proteins).

• Muscle Contraction: Allowing for movement and physical activity.

• Maintaining Temperature: Keeping the body warm, especially in cold environments.

2. Aerobic Respiration

This is the most common and efficient form of respiration, occurring when there is a sufficient supply of oxygen. In eukaryotic cells, it takes place primarily in the mitochondria.

Equations:

• Word: Glucose + Oxygen → Carbon Dioxide + Water

• Chemical: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O

3. Anaerobic Respiration

This occurs when oxygen is in short supply (e.g., during intense exercise like sprinting). It is much less efficient because the glucose is only partially broken down.

In Animals (Humans):

• Equation: Glucose → Lactic Acid

• Key Issues: 1. It releases much less energy than aerobic respiration.

  2. It produces lactic acid, which is toxic and must be removed later.

In Plants and Yeast:

In yeast, this process is known as fermentation.

• Equation: Glucose → Ethanol + Carbon Dioxide

• Industrial Uses: * Bread Making: The CO₂ creates bubbles, making bread light and fluffy.

  • Alcohol Production: The ethanol produced is used to make beer and wine.

4. Summary Comparison