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1. St. Vincent Pallotti School, Besa
Ls. 10 – Respiration in Organisms
Class : VII
Subject : Science
Part : 1

2. In Part I, you will learn about –
▪ Respiration
▪ Aerobic Respiration
▪ Anaerobic Respiration

3. Respiration
• The process of releasing energy from food is called respiration.
• The process of respiration involves taking in oxygen (of air) into the
cells, using it for releasing energy by burning food, and then eliminating
the waste products (carbon dioxide and water) from the body.
• Most living things need oxygen to obtain energy from food. This oxygen
reacts with food (like glucose) present in the body cells and burns them
slowly to release energy.
• This energy is used by the living things.

4. Word Equation for respiration
Glucose Energy
Water
Carbon
dioxide
Oxygen +
+ +
Food Air
Respiration
In body cells
Energy
Carbon dioxide Water
Cell

5. 1)Aerobic Respiration
2)Anaerobic Respiration
Respiration usually takes place in the presence of oxygen. However,
respiration can also take place in absence of air oxygen in air. This means
that breakdown of food to release energy can occur in presence of oxygen as
well as absence of oxygen. Based on this there are two types of respiration:

6. Aerobic Respiration
• When the breakdown of glucose food occurs with the use of oxygen, it is called aerobic
respiration.
• It is called aerobic respiration, because it uses air which contains oxygen (aerobic means
with air).
• In aerobic respiration, the glucose food is completely broken down into carbon dioxide
and water with the use of oxygen, and energy is released.
Glucose Energy
Water
Carbon
dioxide
+
+
Aerobic Respiration
Oxygen

7. Most of the living organisms
carry out aerobic respiration
(by using oxygen of air). For
example, humans (man),
dogs, cats, cows, buffaloes,
goat, deer, birds, lizards,
snakes, earthworms, Frog,
fish and insects (such as
cockroach, grasshopper,
houseflies mosquitoes and
ants, etc.) and most plants
carry out aerobic respiration
by using oxygen of air. The dog obtains energy from its food
through aerobic respiration

8. Anaerobic Respiration
• When the breakdown of glucose (food) occurs without the use of oxygen, it is called
anaerobic respiration.
• It is called anaerobic respiration because it takes place without air which contains oxygen
(anaerobic means without air).
• The microscopic organisms like yeast and certain bacteria obtain energy by anaerobic
respiration.
• In anaerobic respiration, the micro-organisms like yeast break down glucose (food) in the
absence of oxygen to form alcohol and carbon dioxide, and release energy.
Glucose Energy
Alcohol Carbon
dioxide
+
+
Anaerobic Respiration
No oxygen

9. • Yeast is a single celled organism.
• It is used to make alcoholic drinks (such as wine
and beer), and bread.
• Yeast respire anaerobically and during this process,
yeast converts glucose into alcohol.
• Yeast is therefore used in industry to make alcohol.
In bread making the carbon dioxide gas produced
by the yeast makes the bread rise.
• Anaerobic respiration produces much less energy
because only partial breakdown of glucose occurs
in anaerobic respiration in the absence of oxygen.

10. Anaerobic Respiration in Muscles
• Anaerobic respiration takes place in our muscle cells during any vigorous physical
activity when oxygen gets used up faster in the muscle cells than can be supplied by the
blood.
• When anaerobic respiration takes place in our muscle cells in the absence of oxygen, then
glucose (food) breaks down partially to form lactic acid and releases some energy. This
extra energy helps us in doing hard physical exercise.
Glucose Energy
Lactic acid +
Anaerobic Respiration
in muscles
No oxygen

11. After a heavy physical exercise (very fast running,
etc.), we sometimes get muscle cramps (painful
contraction of muscles). This can be explained as
follows:
• The anaerobic respiration by muscles brings
about partial breakdown of glucose (food) to form
lactic acid.
• This lactic acid accumulates in the muscles.
• The accumulation of lactic acid in the muscles causes muscle cramps. Thus, muscle cramps
occur due to the accumulation of lactic acid in muscles when the muscles respire anaerobically
(without oxygen) while doing hard physical exercise.
• We can get relief from cramps in muscles caused by heavy exercise by taking a hot water bath
or a massage.
• Hot water bath (or massage) improves the circulation of blood in the muscles. Due to
improved blood flow, the supply of oxygen to the muscles increases.
• This oxygen breaks down lactic acid accumulated in muscles into carbon dioxide and water,
and hence gives us relief from cramps.