Respiration in Organisms

Why do we Respire?

All organisms are made of small microscopic units called cells. A cell is the smallest structural and functional unit of an organism. Each cell of an organism performs certain functions such as nutrition, transport, excretion and reproduction. To perform these functions, the cell needs energy. Even when we are eating, sleeping or reading we require energy.

The food has stored energy, which is released during respiration. air contains oxygen. We breathe out air which is rich in carbon dioxide. The air we breathe in is transported to all parts of the body and ultimately to each cell.

In the cells, oxygen in the air helps in the breakdown of food. The process of breakdown of food in the cell with the release of energy is called cellular respiration. Cellular respiration takes place in the cells of all organisms. In the cell, the food (glucose) is broken down into carbon dioxide and water using oxygen. When breakdown of glucose occurs with the use of oxygen it is called aerobic respiration. 

Food can also be broken down, without using oxygen. This is called anaerobic respiration. Breakdown of food releases energy. 

Glucose ------(with the use of oxygen) → carbon dioxide + water + energy

There are some organisms such as yeast that can survive in the absence of air. They are called anaerobes. They get energy through anaerobic respiration. In the absence of oxygen, glucose breaks down into alcohol  and carbon dioxide, as given below:

Glucose ---- (without the use of oxygen) →  alcohol + carbon dioxide + energy

Our muscle cells can also respire anaerobically, but only for a short time, when there is a temporary deficiency of oxygen. During heavy exercise, fast running, cycling, walking for many hours or heavy weight lifting, the demand for energy is high. But the supply of oxygen to produce the energy is limited. Then anaerobic respiration takes places in the muscle cells to fulfil the demand of energy:

Glucose --- (in the absence of oxygen)→lactic acid + energy

The cramps occur when muscle cells respire anaerobically. The partial breakdown of glucose produces lactic acid. The accumulation of lactic acid causes muscle cramps. We get relief from cramps after a hot water bath or a massage.  Hot water bath or massage improves circulation of blood. As a result, the supply of oxygen to the muscle cells increases. The increase in the supply of oxygen results in the complete breakdown of lactic acid into carbon dioxide and water.

Yeasts are single-celled organisms. They respire anaerobically and during this process yield alcohol. They are, therefore, used to make wine and beer.

Breathing:

Breathing means taking in air rich in oxygen and giving out air rich in carbon dioxide with the help of

respiratory organs. The taking in of air rich in oxygen into the body is called inhalation and giving out of air rich in carbon dioxide is known as exhalation.

It is a continuous process which goes on all the time and throughout the life of an organism. The number of times a person breathes in a minute is termed as the breathing rate. During breathing inhalation and exhalation take place alternately. A breath means one inhalation plus one exhalation.  Whenever a person needs extra energy, he/she breathes faster.

On an average, an adult human being at rest breathes in and out 15~18 times in a minute. During heavy exercise, the breathing rate can increase upto 25 times per minute. While we exercise, not only do we breathe fast, we also take deep breaths and thus inhale more oxygen.

How Do We Breathe?

Normally we take in air through our nostrils. When we inhale air, it passes through our nostrils into the nasal cavity. From the nasal cavity, the air reaches our lungs through the windpipe. Lungs are present in the chest cavity. This cavity is surrounded by ribs on the sides. A large, muscular sheet called diaphragm forms the floor of the chest cavity. Breathing involves the movement of the diaphragm and the rib cage.

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. 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. These movements in our body can be felt easily.

Notes: Smoking damages lungs. Smoking is also linked to cancer. It must be avoided.

The air around us has various types of unwanted particles, such as smoke, dust, pollens, etc. When we inhale, the particles get trapped in the hair present in our nasal cavity. However, sometimes these particles may get past the hair in the nasal cavity. Then they irritate the lining of the cavity, as a result of which we sneeze. Sneezing expels these foreign particles from the inhaled air and a dust free, clean air enters our body.

Human Respiratory system

 Mechanism of breathing in human beings

Breathing in Other Animals:

Cockroach: 

A cockroach has small openings on the sides of its body. Other insects also have similar openings.  These openings are called spiracles. Insects have a network of air tubes called tracheae for gas exchange. 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. These air tubes or tracheae are found only in insects and not in any other group of animals. 

Earthworm: 

Earthworms breathe through their skins. The skin of an earthworm feels moist and slimy on touching. Gases can easily pass through them. Though frogs have a pair of lungs like human beings, they can also breathe through their skin, which is moist and slippery.

 If cockroaches, snails, fish, earthworms, ants and mosquitoes also have lungs.??

Breathing Under Water:

Gills in fish help them to use oxygen dissolved in water. Gills are projections of the skin. You may wonder how gills help in breathing. Gills are well supplied with blood vessels for exchange of gases. 

Breathing organs in fish

Do Plants Also Respire?:

Like other living organisms, plants also respire for their survival as. They also take in oxygen from the air and give out carbon. dioxide. In the cells oxygen is used to break down glucose into carbon dioxide and water as in other organisms. 

In plants each part can independently take in oxygen from the air and give out carbon dioxide. That the leaves of the plants have tiny pores called stomata for exchange of oxygen and carbon dioxide.

Like all other living cells of the plants, the root cells also need oxygen to generate energy. Roots take

up air from the air spaces present between the soil particles.

Roots absorb air from the soil

Respiration is a vital biological. All living organisms need to respire to get the energy needed for their survival.