Respiration

Respiration is a biochemical process where organisms convert nutrients into energy, which is necessary for their survival. There are two primary types of respiration: aerobic respiration and anaerobic respiration. Each type involves different equations and occurs under different conditions.

1. Aerobic Respiration

Definition

Aerobic respiration occurs in the presence of oxygen. It is the most efficient way to produce ATP (adenosine triphosphate), the energy currency of the cell.

Equation

The overall chemical equation for aerobic respiration is:

The word equation for aerobic respiration is:

glucose + oxygen → carbon dioxide + water + energy released

You need to be able to recognise the chemical symbols:

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy released

Aerobic respiration occurs in several stages:

1. Glycolysis: Takes place in the cytoplasm where one molecule of glucose is broken down into two molecules of pyruvate, yielding a small amount of ATP and NADH.

2. Krebs Cycle (Citric Acid Cycle): The pyruvate enters the mitochondria where it is further oxidized, generating CO2, ATP, NADH, and FADH2.

3. Electron Transport Chain (ETC): Occurs in the inner mitochondrial membrane, where electrons from NADH and FADH2 are passed through protein complexes, ultimately producing a large amount of ATP and water.

Examples

• Human Cells: In muscles during exercise, aerobic respiration provides the energy needed for sustained activities like running or swimming.

• Plants: During photosynthesis, plants also perform aerobic respiration, especially at night when photosynthesis cannot occur.

Usage

Aerobic respiration is primarily used by multicellular organisms, especially during activities requiring sustained energy output. It allows for efficient energy release and is vital for organisms that can access oxygen.

2. Anaerobic Respiration

Definition

Anaerobic respiration occurs in the absence of oxygen and produces less energy compared to aerobic respiration. It is utilized by certain organisms in specific conditions.

Equation

There are different products of anaerobic respiration depending on the organism. Two main forms are:

1. Lactic Acid Fermentation (occurs in muscles):

   glucose → lactic acid

Process

Anaerobic respiration is simpler than aerobic respiration. The process involves:

1. Glycolysis: Just like aerobic respiration, glucose is initially broken down into pyruvate.

2. Fermentation: Instead of entering the Krebs cycle, the pyruvate is converted into lactic acid or ethanol depending on the type of fermentation.

Examples

• Lactic Acid Fermentation: Muscle cells when they engage in high-intensity exercise switch to lactic acid fermentation to produce energy when oxygen is low.

• Alcoholic Fermentation: Yeast cells convert sugar into ethanol and CO2 during brewing and baking processes.

Usage

Anaerobic respiration is mainly used in situations where oxygen is scarce or by organisms that do not require oxygen to survive (anaerobes). It is less efficient in energy production compared to aerobic respiration but allows for survival in extreme conditions.

Conclusion

Both aerobic and anaerobic respiration play crucial roles in the energy metabolism of living organisms. Aerobic respiration is the primary pathway used by most organisms due to its efficiency, while anaerobic respiration is essential in environments devoid of oxygen. Understanding these processes provides insight into cellular energy production and the adaptability of life in varying environments.