The document explains the process of respiration in humans, which involves the intake of oxygen, oxidation of glucose, and release of carbon dioxide and energy. It distinguishes between aerobic and anaerobic respiration, detailing how yeast and muscle cells produce energy and lactic acid, respectively. Additionally, it outlines the mechanics of breathing, the structure and function of lungs, and the process of inhalation and exhalation.

1. Respiration in
Humans
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2. → The process of taking oxygen into the body and
then oxidation of food with this oxygen and
release of carbon dioxide and energy is called
respiration.
→ Process of respiration :-
Intake of oxygen from the environment
Oxidation of glucose with the help of oxygen
Release of energy and carbon dioxide
Elimination of carbon dioxide
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3. Anaerobic respiration
Fermentation by Yeast:-
Anaerobic breakdown of sugars
into alcohol is called
fermentation.
 Yeast is single cell organism. It
respires anaerobically and gives
ethyl alcohol. That is why yeast
is used for making alcohol, vine,
beer. Yeast is used in baking
industry.
Lactic acid formation in muscles:-
 During vigorous muscular
activity, demand of oxygen is
increased but the supply of
oxygen is limited. So, glucose of
the muscles cells breaks down
into lactic acid in less supply of
oxygen.
 Lactic acid produced in the
muscles gets accumulated and
give rise to muscles cramp.
 During massage with oil, blood
supply in muscles increases and
stored lactic acid is now broken
down into carbon dioxide and
water.
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4. Breathing and cellular respiration
Breathing Cellular respiration
 Mechanical process
 Takes place in lungs
 External respiration
 Its process of pumping air
into and out of the lungs
 Chemical process
 Takes place in each and every
cell of our body.
 Release of energy
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5. Aerobic and anaerobic respiration
Aerobic Respiration
Anaerobic Respiration or
(fermentation)
 Breakdown of glucose occurs in
presence of oxygen.
 Organisms that use oxygen for
respiration are called aerobes.
 Glucose is completely oxidised.
 More energy is produced(38 ATP
from one mole of glucose).
 End products are carbon dioxide
and water.
 Example :- Most plants and
animals.
 Glucose is broken down in
absence of oxygen.
 Organisms that can survive and
produce energy in absence of
oxygen are called anaerobes.
 Incomplete oxidation of glucose
takes place.
 Very little energy is produced ( 2
ATP from one mole of glucose).
 End products are ethyl alcohol
and carbon dioxide or lactic acid.
 Example:- yeast, anaerobic
bacteria and parasitic worms.
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6. Organs of breathing
 Nose, nasal passage and wind pipe:-
- We breath air through nose or nostrils.
- In nasal passage the air gets filtered, warmed, and
moistened before entering lungs.
- That is why we should breath with nose and not with
mouth.
- From nasal passage air goes to the wind pipe. Wind pipe is
divided into two bronchi which enters into each lung.
Inside the lungs the bronchi re-divide into smaller and
smaller pipes and finally end into air sacs or alveoli.
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8. Lungs:- (Main respiratory organ)
 Lungs are a pair of spongy, highly elastic and bag like
structure.
 They enclosed thin walled and tiny air sacs called Alveoli.
 The surface of alveoli is covered with a network of blood
capillaries.
 Functions of alveoli:-
1. When we breath in, these alveoli are filled with oxygenated
air. The oxygen from air enters the blood capillaries and the
carbon dioxide from blood comes out.
2. Alveoli has large surface area for the exchange of oxygen
and carbon dioxide between the air in the alveoli and blood
in the alveolar capillaries.
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9. Breathing and breathing rate:-
 Breathing:- Breathing is a mechanical process which
involves taking in of oxygen rich air into the lungs and
giving out carbon dioxide from the lungs.
 Inhalation:- Taking in of air rich in oxygen into the
lungs is called inhalation.
 Exhalation:- Giving out the air rich in carbon dioxide
is known as exhalation.
 One breath:- One breath mean one inhalation and
one exhalation.
 Breathing rate:- The number of times a person
breathes in a minute is termed as breathing rate.
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10. Mechanism of breathing:-
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11. Inhalation and exhalation:-
Inhalation Exhalation
 Ribs move upwards and
outwards
 Diaphragm moves down.
 Due to this the volume of
thoracic cavity increases.
 Lungs increase in size and air
pressure in the lungs decreases.
 Atmosphere have higher air
pressure so, air from atmosphere
rush into the lungs and lungs get
filled with fresh air.
 Ribs move downward and
inward.
 Diaphragm moves up.
 Due to this volume of thoracic
cavity decreases.
 Size of the lungs decrease and
air pressure inside lungs
increases.
 Increased air pressure inside the
lungs push the carbon dioxide
rich air out in atmosphere.
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