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Respiration is the process in which food is broken down into smaller particles along with the liberation of energy. The energy released is utilized for various metabolic activities. In this process oxygen is inhaled inside by a living organism when they breathe in and carbon dioxide is exhaled out. Study about respiratory system for better understanding.

In human beings, oxygen is inhaled inside the human body through nose or mouth. Oxygen is transferred to the entire body and enters the cell. Inside the cell food particles are broken down into smaller pieces in the presence of oxygen. During the breakdown of food particles, energy is released in the form of ATP. This energy released is utilized in certain metabolic activities.

Respiration equation:

C6H12O6 + 6O2 –> 6CO2 + 6H2O + ATP

Respiration process can be of two types:


Aerobic Respiration

Aerobic means “with air”. Therefore, aerobic respiration is the process of cellular respiration that uses oxygen to produce energy from food. This type of respiration is common in most of the plants and animals including humans, birds, and other mammals. While breathing, we inhale air that contains oxygen and we exhale air rich in carbon dioxide. As we breathe in, the oxygen-rich air is transported to all the parts of our body and ultimately to each cell. Inside the cell, the food, which contains glucose, is broken down into carbon dioxide and water with the help of oxygen. The process of breaking down the food particles releases energy, which is then utilized by our body. The energy released via aerobic respiration helps plants and animals, including us, grow.

The process can be simply explained with the help of the following equation:

Glucose + Oxygen → Carbon dioxide + Water + Energy

Aerobic respiration is a continuous process and it happens all the time inside the cells of animals and plants.

Anaerobic Respiration
Anaerobic means “without air”. Therefore, this type of cellular respiration does not use oxygen to produce energy. Sometimes there is not enough oxygen around for some organisms to respire, but they still need the energy to survive. Due to lack of oxygen, they carry out respiration in the absence of oxygen to produce the energy they require, which is referred to as anaerobic respiration. Anaerobic respiration usually occurs in lower plants and microorganisms. In the absence of oxygen, the glucose derived from food is broken down into alcohol and carbon dioxide along with the evolution of energy.

Glucose → Alcohol + Carbon dioxide + Energy

Anaerobic respiration is also used by multi-cellular organisms, like us, as a temporary response to oxygen-less conditions. During heavy exercise, fast running, cycling or weight lifting, our body demands high energy. As the supply of oxygen is limited, the muscle cells inside our body resort to anaerobic respiration to fulfill the energy demand.

How do you feel when you exercise too much? Have you ever wondered why you get those muscle cramps when you run very fast? Anaerobic respiration is the culprit to be blamed. Cramps occur when muscle cells respire anaerobically. Partial breakdown of glucose, due to lack of oxygen, produces lactic acid and the accumulation of lactic acid causes muscle cramps. That is why a hot shower after heavy sports relieve the cramps as it improves blood circulation in the body which in turn enhances the supply of oxygen to the cells.

Glucose → Lactic acid + Energy

Anaerobic respiration produces the relatively lesser amount of energy as compared to aerobic respiration as glucose is not completely broken down in the absence of oxygen.

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