Respiration in Organisms
IMPORTANT TERMS
Anaerobes Organisms which can survive in the absence of air.
Breathing Rate The number of times a person breathes in a minute is termed as the breathing rate.
Stomata Tiny pores for exchange of gases in plants.
Lenticels Pores in the stems or branches of a plant that help in the exchange of gases.
Diaphragm A large muscular sheet that forms the floor of the chest cavity.
Alveoli Lungs have a large surface area which is composed of millions of tiny air sacs called alveoli.
Gills The respiratory organ in fishes.
Spiracles Insects have small openings on the sides of their body called spiracles.
Tracheae Insects have a network of air tubes known as tracheae for exchange of gases.
RESPIRATION
Respiration is the process in which food (glucose) is broken down in body cells through various chemical reactions. During this process, carbon dioxide, water and energy are released. Respiration consists of two processes:
Breathing or External Respiration – It involves the exchange of oxygen and carbon dioxide. Oxygen is taken from the environment and carbon dioxide and water vapour are given out.
Cellular or Internal Respiration – It is the process of breakdown of food in the cell resulting in the release of energy.
TYPES OF RESPIRATION
Aerobic Respiration
When breakdown of glucose occurs with the use of oxygen, it is called aerobic respiration. During this process, the food molecules are combined with oxygen and get oxidised inside cell. They are then broken down into carbon dioxide and water and energy is released.
The word equation for aerobic respiration is:
Glucose + Oxygen ----- > Carbon Dioxide + Water + Energy
Anaerobic Respiration
When food is broken down without using oxygen, it is called anaerobic respiration.
Some organisms such as Yeast undergo anaerobic respiration, wherein glucose breaks down in the absence of oxygen. Here, glucose gets converted into an intermediate compound such as ethanol and carbon dioxide and energy is released.
Glucose --- > Ethanol + Carbon dioxide + Energy
Human muscles can also respire anaerobically when there is a temporary deficiency of oxygen. During heavy exercise, the demand for energy is high and the supply of oxygen to produce energy is limited. The lungs cannot supply sufficient oxygen to the muscles quickly so the muscle cells respire anaerobically. Here, glucose is broken down into lactic acid, without oxygen and energy is released. The word equation for anaerobic respiration is:
Glucose --- > Lactic Acid + Energy
The accumulation of lactic acid causes muscle cramps.
MECHANISM OF BREATHING
Breathing or external respiration involves the exchange of oxygen and carbon dioxide.
Inhalation
During breathing, the process of taking-in of air that is rich in oxygen is known as inhalation. The lungs expand during the process of inhalation. The ribs move up and outwards and diaphragm pushes down and becomes flat. As a result, the chest expands and the volume increases. The lungs get filled with air.
Exhalation
During breathing, the process of giving out of the air rich in carbon dioxide is known as exhalation. When we breathe out, the air escapes from the lungs. During exhalation, ribs move down and inwards and diaphragm moves up to its former position. The size of the chest cavity gets reduced and air is pushed out of the lungs.
RESPIRATION IN HUMANS
The main organs of respiration in human beings are lungs. Lungs are present in the chest cavity. They have a large surface area which is composed of millions of tiny air sacs called alveoli, where the exchange of gases takes place.
The air rich in oxygen is taken-in through nostrils; from there it enters the nasal cavity. From the nasal cavity, the air reaches the lungs through the windpipe.
BREATHING IN OTHER ANIMALS
Cockroach
Insects such as cockroach, housefly have small openings on the sides of their body which are called spiracles. They have a network of air tubes called tracheae for the exchange of gases. Oxygen passes through spiracles and reaches the tracheal tubes. It further, diffuses into the body tissue and reaches every cell of the body.
Earthworm
Earthworms breathe through their skin. They have moist skin which is supplied with a network of tiny blood vessels which absorb oxygen and supply it to the rest of the body.
Frog
Frogs have a pair of lungs but they can also breathe through their skin, which is moist and slippery and is supplied with blood capillaries.
Fish
Fishes and other aquatic animals absorb dissolved oxygen with the help of gills, which are projections of the skin. They are well supplied with blood vessels for exchange of gases.
RESPIRATION IN PLANTS
Leaves are the main respiratory organ in plants. The process of respiration takes place through tiny pores in the leaves known as stomata. Stomata remain open during the day but at night they are closed. The opening and closing of stomata is controlled by the guard cells.
The stems of the plants have pores called lenticels which also help in the exchange of gases. The parts above the soil get their oxygen also through lenticels. Lenticels do not close or open like stomata, so it is important for respiration during the night when stomata are closed.
The roots get oxygen from the air spaces in the soil.
INTERESTING FACTS
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