Class 7 Science

Respiration

Learning Goals

The biological process in which food is utilized to produce energy is called respiration. Respiration is necessary for survival of living beings. A living being cannot survive even for a few seconds, without respiration. During respiration, it is mainly the carbohydrate which is oxidized to produce energy. This can be shown by following equation:

Carbohydrate + Oxygen → Carbon dioxide + Water + Energy

C6H12O6 + 6O2 → 6CO2 + 6H2 + Energy

Site of Respiration: Respiration happens inside the cells. As respiration happens inside the cell, it is also called cellular respiration. A cell organelle, called mitochondria is the site of cellular respiration.

Types of Respiration

Aerobic Respiration

Aerobic respiration takes place in the presence of oxygen. Carbon dioxide and water are the end products of aerobic respiration. Aerobic respiration happens in most of the organisms.

Glucose (Presence of oxygen) → Carbon dioxide + Water + Energy

Anaerobic Respiration

Anaerobic respiration takes place in the absence of oxygen. Anaerobic respiration usually happens in most of the microbes. Alcohol and carbon dioxide are formed at the end of anaerobic respiration. In some cases, lactic acid is formed at the end of anaerobic respiration.

Glucose (absence of oxygen) → Alcohol + Carbon dioxide + Energy

Glucose (absence of oxygen) → Lactic acid + Energy

Anaerobic respiration also happens in our muscle cells. When someone runs or walks too fast, one may feel a throbbing pain in calf muscles. This happens because of deposition of lactic acid, produced by anaerobic respiration. Once the person takes rest for some time, the pain goes away.

Review Questions

What is respiration?

Answer: Respiration is a biological process in which food is utilized to produce energy.

What is the end product of respiration in most of the organisms?

Answer: Carbon dioxide and water

What is the end product of anaerobic respiration in muscle cells?

Answer: Lactic Acid

Breathing

The process of taking in and giving out air, for respiration, is called breathing. Breathing involves two man steps, viz. inhalation and exhalation. During inhalation, we breathe in air which is rich in oxygen. During exhalation, we breathe out air which is rich in carbon dioxide.

Rate of Breathing

When we are doing normal activities, the rate of breathing is normal. The rate of breathing increases when we do strenuous physical works, such as running, swimming, jogging, etc. The rate of breathing decreases when we take rest or when we are sleeping.