Breathing

We can live without food for a week, without water a day or two, but

without breathing? Not more than a minute. All of us are alive because

we breathe, not just humans, but plants and animals also breathe. But

how do we breathe? Let us find out below!

What is Breathing?

Breathing is a mechanical Process. In breathing, an organism takes in

oxygen from its environment and released carbon- dioxide.Breathing

involves the transport of oxygen and carbon dioxide between the

external environment and the body cells. This process is also called

pulmonary respiration.

Organisms carry out external respiration in various ways depending on

their size and environment. For example, exchange of oxygen and

carbon dioxide happens directly with the environment through any cell

membrane. In human beings and some animals, lungs are the chief

organs of breathing.

Browse more Topics under Respiration In Organism

● Respiration and Its Types

● Human Respiration

● Respiration in Other Animals

● Respiration in Plants

Types Of Breathing

The process of breathing consists of two types:

● Inspiration or Inhalation: Taking atmospheric air into the lungs.

This process is inhalation. And it depends on the pressure

inside to the lungs. When atmospheric air pressure is more than

the air pressure in lungs, then air enters to the lungs.

● Expiration or exhalation: This is the process that involves

discharging the air from lungs. When the air pressure in lungs

increases and there’s a decrease in the atmospheric pressure

then air comes out from lungs into the environment.

Breathing is the combination of Expiration and Inspiration:

Component Inhaled Exhaled Explanation

Oxygen 21% 16% During respiration cell uses up the

Oxygen.

Carbon

dioxide 0.03% 4% Production of carbon dioxide

occurs as a waste product of

respiration.

Nitrogen 78% 78% Cells do not use nitrogen gas.

Water Variable High Some of the water evaporates and

is lost as air which is breathed out

Comparison Between Breathing and Cellular Respiration

S.N

o Breathing Cellular respiration

1.. It is a physical process in which

oxygen is taken in and carbon

dioxide is given out.

It is a biochemical process in which glucose is

oxidised to carbon dioxide and water.

2. It consumes energy. It liberates energy.

3. It is an extracellular process It is an intracellular process.

4. Enzymes are not used in this

process. Enzymes are used in this process.

How Do We Breathe: Respiration

Breathing is the process that involves taking atmospheric air into

lungs, where an exchange of gases and foul air occurs which is

eventually expelled out from the lungs. The main muscles during

respiration or breathing are Intercostal (external) muscles and

diaphragm. Larynx does not contribute to the breathing movements.

● The muscles of a rib (intercostal) and diaphragm are

responsible for intake and output of air from lungs.

● Inspiration is the result of muscle contraction so it is an active

process.

● During inspiration, the diaphragm and external intercostals

muscles contract simultaneously. Muscles move the lateral

thoracic walls outward and upward.

● To take in the air into lungs, the diaphragm must be flattened.

● Expiration is the result of muscles relaxation so it is a passive

process.

● During expiration, the diaphragm and external intercostals

muscles relax simultaneously. Muscles move the lateral

thoracic walls inward and downward which result in the

exhalation of air.

Breathing rate is lowest while we are sleeping. During normal

breathing, the respiratory movements occur about:

Age Rate

Newborn child 32/min

5-year-old 26/min

25-year-old 16/min

50-year-old 18/min

Question For You

Q. When is the breathing rate at its lowest?

Sol: The breathing rate is at its lowest during the night because our

body is in rest at night.

Respiration And Its Types

We breathe normally with the help of oxygen, but did you know there

are few organisms that can breathe without oxygen? Isn’t it

intriguing? Let us more about types of respiration.

Respiration

All living organisms need the energy to perform various activities and

to maintain life. This energy is obtained from food by a process called

respiration. In animals, cells produce chemical energy from

degradation of the organic compound and in other plant decomposed

food from photosynthesis process.

Thus Respiration is an important biochemical reaction process of

oxidation by which food materials are oxidized to produce carbon

dioxide, water, and energy.

Types of Respiration

There are two types of respiration which we classify on the basis of

the presence or absence of oxygen:

Aerobic respiration

The respiration that takes place in the presence of oxygen is called

aerobic respiration because it uses ‘air’ which contains oxygen. The

aerobic respiration involves utilization of oxygen for the breakdown of

chemical bonds in glucose to release energy in high amounts. It is the

chief source of energy for plants and animals. Animals and plants that

use oxygen for respiration are aerobes. Majority of animals have

aerobic respiration.

C

6

H

12

O

6

+6

O

2

⟶6

CO

2

+6

H

2

O+Energy

All the organisms that obtain energy by aerobic respiration cannot live

without the oxygen. This is because if there is no oxygen, they cannot

get energy from the food which they eat. Aerobic respiration produces

more energy because a complete breakdown of glucose occurs during

respiration by the use of oxygen.

Anaerobic Respiration

The respiration that takes place in the absence of oxygen is anaerobic

respiration. In this process, incomplete oxidation of food material is

being and produces carbon dioxide and alcohol. Beside this other

organic matter like citric acid, oxalic acid, lactic acid, etc are also

produced.

This process is also known as intramolecular Respiration. The

anaerobic respiration takes place in organisms like yeast, some

bacteria, and parasitic worms. The animals and plants that can survive

and obtain energy even in the absence of oxygen are called Anaerobic.

Glucose⟶Alcohol+C

O

2

+Energy

Yeast is a single-celled fungus. In yeast, a single cell represents the

whole organism. Very low amount of energy is realised in this

process. Yeast respires anaerobically and during this process, yeast

converts glucose into alcohol. Therefore it is used to make alcohol

bread, etc.

Anaerobic respiration produces much less energy because the only

partial breakdown of glucose occurs in anaerobic respiration in the

absence of oxygen. All the organisms which obtain energy by

anaerobic respiration can live without the oxygen.

For example, yeast is an organism which can live without the oxygen

of air because it obtains energy by the process of anaerobic

respiration. Yeast can survive in the absence of oxygen.

Anaerobic Respiration in Muscles

Human beings normally obtain energy by aerobic respiration. But

when we need extra energy, anaerobic respiration can take place in

our muscles for a short time. When we do a heavy physical exercise,

our muscles need more oxygen. But the supply of oxygen through

blood is limited and hence insufficient.

During heavy exercise, Some of our muscles respire anaerobically.

The anaerobic respiration by muscles brings about the partial

breakdown of glucose to form lactic acid. This lactic acid accumulates

in the muscles. The accumulation of lactic acid in the muscles causes

muscles cramps.

Yeast are single-celled organisms. They respire anaerobically and

yield ethyl alcohol and are used to make wine and beer. They are also

used in baking industry.

Aerobic versus Anaerobic Respiration

S.No Aerobic respiration Anaerobic respiration

1. It occurs in the presence of oxygen. It occurs in the absence of oxygen.

2 Food materials are completely

oxidised to release carbon dioxide,

water and energy.

Food materials are incompletely oxidised

to release alcohol, carbon dioxide and

energy.

3. Sufficient amount of energy is

released. A small amount of energy is released.

4. It takes places in all organisms. It Takes place in very few organisms like

yeast and in muscles of the human

beings.

5. Enzymes responsible for this

process are found in mitochondria. Enzymes responsible for this process are

found in protoplasm.

Similarities Between Aerobic and Anaerobic Respiration

Aerobic respiration Anaerobic respiration

1 In aerobic respiration, energy is

produced by the breakdown of

food(like glucose).

In anaerobic respiration, energy is also

produced by the breakdown of food (like

glucose).

2 Aerobic respiration takes place in

the cells of the organism. Anaerobic respiration also takes place in

the cells of the organism

Question For You

Q. In which human part, anaerobic respiration can take place?

Sol: Anaerobic respiration in humans can take place in muscles.

Human Respiration

When you run, after some time don’t you run of breath and your

breathing becomes heavy? But why does this happen? Well, this

happens because your body at that moment needs more oxygen. In

human respiration, we breathe in oxygen and breathe out

carbon-dioxide. But is human respiration only this? Let us know

more!

Human Respiration

In all higher living organisms, the respiratory organ is lungs and

gaseous exchange takes place from these lungs. The lungs are the

most important organs that help human beings in respiration. Air is

sucked into the lungs through a series of cavities and tubes which

together make up the whole respiratory system.

Respiratory system in higher organisms is divided into two parts-

● Associate organs

● Main organs

Associate Organs

1. Nostril

Air enters the body through the nose. Externally, the nose consists of

two nostrils. Nostrils are lined with membranes that are coated with a

moist, sticky mucus. Some of the membranes have moving cilia.

As air passes over the membranes, it is warmed and moistened. Dust

particles falling on the sticky surface are swept out by cilia, towards

the throat, where they are either swallowed or coughed up. This

removes most of the large foreign particles from the air.

2. Throat and Pharynx

The nasal cavity leads into the Pharynx. Posterior part of the nasal

passage is called pharynx which is connected to the mouth. The air

passes through the pharynx and enters the trachea, or windpipe, which

is in the middle of the neck. The trachea is about 12 cm long and

2.5cm in diameter.

(Source: Unacademy)

3. Larynx

The larynx is a sound producing organ which is the enlarged upper

end of the trachea. Its occur four type of cartilages-(a) One thyroid (b)

One Cricoid (c) paired arytenoids cartilages, which have one pair of

the vocal cord, it is a sound producing organs.

4. Bronchi

The trachea divides into two tubes, The right and left bronchi. After

air has passed through the trachea, it enters the bronchi. Each

bronchus enters a lung. Air is further pulled into branches of the

bronchi. The bronchi then divide into smaller tubes called bronchioles.

The bronchioles connect to tiny ducts that lead into air sacs called

alveoli. Alveoli are usually surrounded by tiny blood vessels. It is in

the alveoli of the lungs where gaseous exchange occurs. Oxygen from

the alveoli passes into the blood cells and is carried to different parts

of the body. At the same time, carbon dioxide from the blood vessels

passes into the alveoli.

5. The Thoracic Cavity and Diaphragm

The thoracic cavity is hollow cavity divided into two pleural cavities

each enclosing a lung. The floor of the thoracic cavity is completely

closed by a thin muscular septum called diaphragm. The thorax is

separated from the abdomen below by the diaphragm.

6. Lungs – Main Organ

The lungs are a pair of elastic organs present in the chest or pleural

cavity of the body. The sides of the chest are bounded by the ribs,

which are joined to the backbone at the back and the breastbone at the

front. The pleural cavity contains pleural fluid allows membranes to

move easily on one another while breathing and keeping lungs always

moist and help them in the breathing process.

The right lungs are somewhat larger than the left lung and are divided

into three lobes, while the left lung is divided into two lobes Adult

lungs have an internal area near about 90meter square.The whole area

is covered with a net of tiny blood vessels, which is joined, end to end

cover several thousand meters.

Question For You

Q. In the normal expiration, the diaphragm is:

a. Arched

b. Flattened

c. Not involved

d. Perforated

Sol: a. Arched

During expiration, the intercostal muscles and the diaphragm are

relaxed leading to decrease in the volume of the thoracic cavity so that

the air is expired from the lungs. The relaxed diaphragm gets arched

up forming a dome.

Respiration in Other Animals

Do humans and animals breathe similarly? Does respiration in animals

occur similarly? Above all, do all animals breath in a similar fashion?

Let us know more!

Introduction

Respiration is an oxidation process which involves degradation of a

complex organic compound, hence carbon dioxide and water and

energy are produced. Respiration process can be divided into two

phases –

External Respiration or Breathing

In this process, animals intake oxygen and release carbon dioxide. It is

also known as breathing. This is mainly two phases.

● Inspiration: It is the process by means of which oxygen is taken

to the lungs.

● Expiration: During expiration, carbon dioxide is expelled out

from the respiratory organs into the environment.

Internal Respiration or Cellular Respiration

In this process, oxygen is used in chemical reactions within the cells.

These reactions release energy from food substances and produced

carbon dioxide and water as waste products.

Sugar+

O

2

⟶

CO

2

+

H

2

O+Energy

Respiration in Animals

The mode of external respiration varies greatly from organism to

organism. The basic process of respiration (cellular respiration) is

similar in all living organisms. The process of exchange gases varies

in different animals.

1. Through Plasma Membrane

In unicellular animals, such as amoeba, exchange of gases takes place

through cell surface. They absorb oxygen from the surrounding air or

water and give out carbon dioxide through plasma membrane by

diffusion.

2. Through Body Wall or Skin

Tapeworms, earthworms, and leeches use their skin for the exchange

of gases. The skin of Earthworms is very thin and moistened. Many

blood cells are spread on this skin. These blood cells are known as

capillaries. The exchange of gases occurs at capillaries. They die of

suffocation if their skin is dried up.

Amphibians such as frogs use more than one organ of respiration

during their life. They breathe through gills while they are tadpoles.

Mature frogs breathe mainly with lungs and also exchange gas with

the environment through skin.

3. Through Tracheal System

In insects like cockroaches, grasshopper, transportation of gas or

gaseous exchange take place by a special type of fine tubes is called

tracheae.

Air containing oxygen enters through spiracles into the tracheal tubes.

It then diffuses into the body tissue and reaches every cell in the body.

Carbon dioxide released from the cells goes into the tracheal tubes and

comes out through spiracles.

4. Through Gills

A majority of aquatic animals like fish and prawns breathe through

special organs called gills. Gilla are projections of the skin that help in

using oxygen dissolved in water. Gills contain blood vessels which

help in exchange of gases.

Fish live in water. To get oxygen dissolved in water, fish gulp water

through the mouth and pump it over the gills. Water passes into the

gill chamber through gill slits. In each chamber, the water passes over

the filaments. They absorb oxygen from the water and replace it with

carbon dioxide formed. The water then passes out through the gill

opening and this process is repeated again and again.

5. Through lungs

Amphibians, mammals, and birds exchange gases through special

respiratory organs called lungs. Lungs are air-filled sac-like structures

in the chest cavity. They are connected to the outside by a series of

tubes and small opening.

Question For You

Q. Fishes absorb oxygen from

a. air

b. water

c. earth

d. none of above

Sol: b. water. Fishes live in water. To get oxygen dissolved in water,

fish gulp water through the mouth and pump it over the gills. Water

passes into the gill chamber through gill slits. In each chamber, the

water passes over the filaments. They absorb oxygen from the water

and replace it with carbon dioxide formed.

Respiration in Plants

Humans breathe, animals breathe, but do plants also breathe? Yes! Of

course, plants breathe as well. We may not be able to see the process

of respiration in plants, but it is happening. Let study below about

respiration in plants.

Respiration in Plants

Plants like other animals also respire. Plants also need energy. The

plants get energy through the process of respiration in which glucose

food breaks down in the presence of oxygen to form carbon dioxide

and water with the release of energy.

This energy is used by the plant for carrying out its various life

processes. Thus, Like other organisms, plants also respire for their

survival. The respiration in plants differs from that of animals. In other

words, in plants, each part can independently take in oxygen from air,

utilize it to obtain energy, and give out carbon dioxide.

Browse more Topics under Respiration In Organism

● Breathing

● Respiration and Its Types

● Human Respiration

● Respiration in Other Animals

Learn more about Respiration in Animals here.

Respiration In Leaves

The leaves of plants have tiny pores on their surface which are called

stomata. The exchange of gases in the leaves during respiration takes

place through stomata.

This happens as follows: Oxygen from the air enters into a leaf

through stomata and reaches all the cells by the process of diffusion.

This oxygen is used in respiration in cells of the leaf. The carbon

dioxide produced during diffuses out from the leaf into the air through

same stomata.

The photosynthesis reaction makes glucose and the respiration

reaction break it down. In photosynthesis, the energy which goes into

the reaction is light energy. In respiration, the energy which comes out

is chemical energy.

Respiration in Roots

The roots of plants are under the ground but root cells also need

oxygen to carry out respiration and release energy for their own use.

How Does Respiration Occur in Roots?

The roots of a plant take up air from the spaces between the soil

particles. Root hairs are in contact with the air in the soil particles.

Oxygen from the air in soil particles diffuse into root hair and reach all

the cells of the root where it is utilised in respiration. Carbon dioxide

produced in the cells of the root during respiration goes out through

the same root hair by the process of diffusion.

If a potted plant is over watered for a long time, then the plant may

ultimately die. This is because too much water expels all the air from

in between the soil particles. Due to this, oxygen is not available to the

roots for aerobic respiration. In this condition, the roots of plant

respire anaerobically producing alcohol. This may kill the plant.

Germinating seeds during early stage respire anaerobically because

they have seed coat which does not allow the oxygen to enter through

it.

Respiration in plants happens throughout the day and night thereby

carbon dioxide is produced. However, during the daytime, the amount

of carbon dioxide released is negligible compared to the amount of

oxygen produced as a result of photosynthesis. Hence, one should not

sleep under a tree at night.

Learn more about Respiration and its types.

Question For You

Q1. From where do roots absorb air needed for respiration?

Ans: Root hairs

Q2. Name the tiny pores on the surface of leaves of a plant through

which gas exchange occurs.

Ans: Stomata

Q3. Name any two parts of the plant through which exchange of gases

takes place during respiration.

Ans: Roots and Leaves.