Respiration

Respiration is the process by which living organisms use food to produce energy. It is an oxidation reaction where carbohydrates are broken down to release energy.

• First, glucose (a six-carbon molecule) breaks down into pyruvate (a three-carbon molecule) in the cytoplasm. Then, in the mitochondria, pyruvate breaks down further into carbon dioxide with the help of oxygen.
• Different organisms have different organs for respiration. Animals like fish, snakes, and mice use special respiratory organs, while plants use tiny pores on their stems and leaves. Respiration is essential for all living beings.

Respiration involves:

1. Gaseous exchange (breathing): Intake of oxygen from the atmosphere and release of carbon dioxide
2. Cellular respiration: The breakdown of simple food molecules to release energy inside the cell.

Respiration in living things

1. Aerobic respiration: This type of respiration occurs in the presence of oxygen. Pyruvic acid is converted into carbon dioxide. Energy is released, and a water molecule is also formed at the end of this process.
2. Anaerobic respiration: This type of respiration happens without oxygen. Pyruvic acid is either converted into ethyl alcohol or lactic acid. Ethyl alcohol is usually formed during anaerobic respiration in microbes like yeast or bacteria, while lactic acid is formed in some microbes and muscle cells.

The above diagram shows us the breakdown of glucose by various pathways.

The energy released during cellular respiration immediately synthesises an ATP molecule, which fuels all other cell activities. In these processes, ATP is broken down, giving rise to a fixed amount of energy, which can cause endothermic reactions in the cell.

Aquatic organisms breathe much faster than terrestrial organisms because the amount of dissolved oxygen in the water is relatively low compared to the amount in the air.