Respiration

The process by which a living being utilises the food to get energy is called respiration. Respiration is an oxidation reaction in which carbohydrate is oxidised to produce energy.

• The first step is the breakdown of glucose, a six-carbon molecule, into a three-carbon molecule called pyruvate. This process takes place in the cytoplasm.
• This process breaks up the three-carbon pyruvate molecule to give three molecules of carbon dioxide. The breakdown of pyruvate using oxygen takes place in the mitochondria.
• Animals like fish, snakes, and mice have specific organs for respiration. And plants breathe through tiny pores found on their stems and leaves. Respiration is a key feature of all living things.

Respiration in living things

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.

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.