Respiration in Organisms
The process of breakdown of food in the cell with the release of energy is called cellular respiration. It is of two types namely, aerobic respiration and anaerobic respiration.
Aerobic respiration is a complex process of chemical reactions, in which oxygen is used to break down glucose into carbon dioxide and water. The energy is released in the form of ATP.
Respiration sometimes occurs without oxygen, and this is called anaerobic respiration. In this type of respiration, glucose is partially broken down and the end products are lactic acid or ethanol (alcohol), carbon dioxide and energy; this process is known as fermentation. Yeasts are single-celled organisms which respire anaerobically and yield alcohol during this process.
During heavy exercise i.e. fast running, cycling etc., the demand for energy is high and supply of oxygen to produce energy is limited, then anaerobic respiration takes places in the muscle cells to fulfill the fast demand of energy.
Breathing means taking in air rich in oxygen and giving out air rich in carbon dioxide. It is a physical process, involved in respiration. It involves two processes namely, inhalation and exhalation.
Inhalation is the movement of air from the external environment, through the air ways, into the alveoli.
Exhalation or expiration is the movement of air out of the bronchial tubes, through the airways to the external environment.
When we inhale air, it passes through our nostrils into the nasal cavity. The muscles of nostrils and the muscular diaphragm play a key role in breathing.
From the nasal cavity, the air reaches our lungs through the windpipe, which is present inside the chest cavity. During inhalation, ribs move up and outwards and diaphragm moves down. This movement increases space in our chest cavity and air rushes into the lungs and the lungs get filled with air.
During exhalation, ribs move down and inwards, while diaphragm moves up to its former position. This reduces the size of the chest cavity and air is pushed out of the lungs.
Different types of organisms show different mechanisms for respiration.
Insects generally have a network of air tubes called tracheae for gas exchange. Insects possess small openings on the sides of their body, known as spiracles. Oxygen rich air rushes through spiracles into the tracheal tubes, diffuses into the body tissue, and reaches every cell of the body. Similarly, carbon dioxide from the cells goes into the tracheal tubes and moves out through spiracles. E.g., in cockroach.
An earthworm breaths through its moist skin. Oxygen from air dissolves in the moisture present on the skin and then travels into the skin blood capillaries. The blood carries oxygen to various parts of the body and CO2 is lost from the body by the opposite process.
The gills in fish help them to use oxygen dissolved in water.
In plants, each part can independently take in oxygen from the air and give out carbon dioxide. The leaves of the plants have tiny pores called stomata for exchange of oxygen and carbon dioxide.