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. Therefore, all
living organisms respire to get energy from food. During breathing, we breathe
in air containing 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.
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:
Yeasts
are single-celled organisms. They respire anaerobically and during this process
yield alcohol. They are, therefore, used to make wine and beer.
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:
Why
you get muscle cramps after heavy exercise? Why we get relief from cramps after
a hot water bath or a massage?
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.
BREATHING
Breathing
is a part of respiration. Air is a
mixture of gases. 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.
Mathematically,
Breathing rate = number of breaths/minute
Both
inhalation and exhalation take place. A breath means one inhalation plus one
exhalation.
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.
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 dustfree, clean air enters our body.
TAKE
CARE: When you sneeze, you should cover your nose so that the foreign particles
you expel are not inhaled by other persons.
MECHANISM OF BREATHING IN HUMAN BEINGS
BREATHING
IN OTHER ANIMALS
Animals
such as elephants, lions, cows, goats, frogs, lizards, snakes, birds, have
lungs in their chest cavities like the human beings.
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
pair of lungs like human beings, they can also breathe through their skin,
which is moist and slippery.
BREATHING
UNDER WATER
Gills
are breathing organ in fish.These helps fish to use oxygen dissolved in water.
Gills are projections of the skin. Gills are well supplied with blood vessels
for exchange of gases.
DO
PLANTS ALSO RESPIRE?
Like
other living organisms, plants also respire for their survival. They also take
in oxygen from the air and give out carbon dioxide. 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.
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