• CLASS-7

CHAPTER-10

RESPIRATION IN ORGANISMS

Why do we respire ?

We respire to get energy from food. Food contains stored energy. When we respire the food is broken down in the cells of our body with the help of oxygen and energy is released.

Respiration :- is the process by which food (glucose) is broken down in the cells of the body with the help of oxygen to release energy.

Since respiration takes place in the cells of the body, it is called cellular respiration.

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Glucose + Oxygen Carbon dioxide + Water + Energy

Living things respire.

• Respiration is a process that gives energy from stored food.
• During respiration, exchange of gases takes place.
• The movement of air in and out of the body for respiration is known as breathing.

For example, animals such as earthworms breathe through their skin; fishes use gills for breathing and plants exchange gases through tiny pores called stomata, which are present mainly on the surface of leaves.

Types of respiration :-

There are two types of respiration. They are aerobic respiration and anaerobic respiration.

i) Aerobic respiration :- is respiration in which glucose is broken down in the presence of oxygen to release carbon dioxide, water and energy. It takes place in most organisms.

Presence of oxygen

Glucose carbon dioxide + water + energy

ii) Anaerobic respiration :- is respiration in which glucose is broken down in the absence of oxygen to release alcohol, carbon dioxide and energy. It takes place in yeast.

Absence of oxygen

Glucose alcohol + carbon dioxide + energy

In anaerobic respiration in our muscle cells glucose is broken down in the absence of oxygen to release lactic acid and energy.

Absence of oxygen

Glucose lactic acid + energy

Difference between Aerobic and Anaerobic respiration

Adenosine triphosphate (ATP) is the universal unit of energy used in all living cells.It is the very basic molecule which meets our energy needs and is formed in the later steps of glucose oxidation.

Aerobic respiration presented by the equation:

^C6^H12^O6

sugar

(glucose)

+ 6O₂ 6CO₂ + 6H₂O + energy

oxygen

carbon dioxide

water

This means that one molecule of sugar reacts with six molecules of oxygen to produce six molecules of carbon dioxide and six molecules of water.

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Energy is released during this process

Anaerobic respiration represented by the equation:

^C6^H12^O6

glucose

2C₂H₅OH+2CO₂

alcohol

energy

The energy released by anaerobic respiration is considerably less than the energy from aerobic respiration.

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Anaerobic respiration takes place at some stage in the cells of most living organisms.

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For example, our own muscles resort to anaerobic respiration when oxygen is not delivered to them fast enough.

ANAEROBIC RESPIRATION

• Yeast (important in brewing and baking) :

- Glucose →alcohol+carbon dioxide + Energy C₆H₁₂O₆ → 2C₂H₅OH +2CO₂ +Energy

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• Animals (in muscle cells during exercise):

- Glucose → lactic acid + Energy

- C₆H₁₂O₆ → 2 C₃H₆O₃ + Energy

YEAST

Yeast are unicellular organisms.

They respire anaerobic in the absence of oxygen.

During anaerobic respiration they produces alcohol.that is why they are used for making wine and beer.

Yeast

0.005mm

Yeast cells dividing

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Single yeast cell

cell wall

nucleus

cytoplasm

vacuole

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Anaerobic Respiration

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EXTRA ENERGY CAN BE PRODUCED BY ANAEROBIC RESPIRATION

• Glucose

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→ lactic acid + energy

During heavy exercises, cycling or running, the demand for energy increases.

Then muscle cells undergo anaerobic respiration due to deficiency of oxygen.

Partial breakdown of glucose into lactic acid causes muscle cramps.

We can relief from cramps after a hot water bath or hot massage.

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EFFECT OF LACTIC ACID IN MUSCLES DURING EXERCISE

• Muscles respire aerobically, but when they are working hard a lot of energy is needed.
• We breathe deeper and faster to get more O₂ into our blood.
• Our heart beats faster to get the O₂ to the leg muscles as quickly as possible.
• A limit is reached, but we still need more energy.

EXERCISE CAN CREATE AN O₂ DEBT

Question 1

What is the most important point about respiration?

1. it uses oxygen
2. It produces energy
3. It produces carbon dioxide
4. It needs food and air

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Question 2

In which part of the human body is respiration most likely to be occurring?

1. The lungs
2. The heart
3. The muscles
4. All of these

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Question 3

Which of these are waste products of respiration?

1. Carbon dioxide
2. Water
3. Oxygen
4. Nitrogen

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Question 4

Which of the following would be reliable indicators of respiration in a living organism?

1. Output of water vapour (H₂O)
2. Output of carbon dioxide (CO₂)
3. Uptake of oxygen (O₂)
4. Production of energy

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Question 5

Which of the following statements are correct?

1. We breathe in air
2. We breathe in oxygen
3. We breathe out air
4. We breathe out carbon dioxide

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ANSWERS:

1. (b) It produces energy

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• (d) all of these

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• (a) carbon di oxide

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• (d) production of energy

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• (a) and (c) We breathe in air and we breathe out air

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Respiration in ourselves:

1. Air taken in
1. Food taken in

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• 3.The blood stream carries glucose and oxygen to the muscles

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• 5 Carbon dioxide
• is carried to the lungs by the blood

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2. The lungs absorb oxygen from the air

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2.The stomach and intestine digest food. One of the products is glucose

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4 RESPIRATION

Glucose and oxygen react to produce energy for muscle contraction

Some examples of the use of energy in organisms

Respiration supplies

the energy for

muscle contraction

germination

cell division

chemical changes in cells

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Breathing :-

Breathing is the process by which oxygen rich air is taken in and carbon dioxide rich air is given out with the help of the respiratory organs.

The taking in of air rich in oxygen is called inhalation. The giving out of air rich in carbon dioxide is called exhalation.

Breathing rate :-The number of times a person breathes in a minute is called the breathing rate. (Number of breaths per minute)

When a person needs more energy, he breathes faster, more oxygen is supplied to the cells, more food is broken down and more energy is released.

How do we breathe ?

The respiratory system helps in breathing. The main parts of the respiratory system are nostrils, nasal cavity, wind pipe, lungs and diaphragm.

Breathing involves the rib cage and a muscular sheet below the chest cavity called diaphragm.

During inhalation (breathing in) the chest cavity increases in size and the diaphragm moves down and air enters into the lungs. During exhalation (breathing out) the chest cavity reduces in size and the diaphragm moves up and air is pushed out of the lungs.

The Human Respiratory System

Mechanism of breathing

Model to show the mechanism of breathing

What do we breathe out ?

The air we breathe is a mixture of carbon dioxide and moisture :-

Activity :-

Take a test tube and pour some lime water into it. Insert a plastic straw into the lime water. Blow air through the straw into the lime water. The lime water turns milky. This shows that the air we breathe out contains carbon dioxide.

Take a mirror and blow air on the mirror. A film of moisture is formed on the mirror. This shows that the air we breathe out contains moisture.

Breathing in other animals :-

i) Cockroach :-

Cockroach breathes through small openings in their body called spiracles. The spiracles are connected to air tubes called trachea. Oxygen rich air enters through the spiracles and passes through the trachea to all cells in the body. Carbon dioxide from the cells passes through the trachea and spiracles out of the body.

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Respiration in Amoeba:

Amoeba respires by the process of diffusion through its body surface.

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Respiration in land animals:

Organisms such as elephants, lions, cows, frogs, and birds have lungs like that in human beings.

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Respiration in frog:

Frogs have a pair of lungs like human beings . They can breathe through their moist skin as well.

Respiration in Earthworm :-

Earthworms breathe through their moist skin. The moist skin helps in the exchange of gases.

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Respiration in Fishes :-

Fishes breathe through gills. The gills have blood vessels which help in the exchange of gases.

Respiration in plants :-

Plants also take in oxygen from air and give out carbon dioxide. This oxygen is used in the cells to break down glucose into carbon dioxide and water and release energy.

The leaves have tiny pores called stomata which helps in the exchange of gases. The root hair also help to take air from the soil.

ROOTS ALSO RESPIRE:

Like other living cells, roots of the plants also need oxygen for respiration.

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Roots take up air from air space present between the soil particles by the process of diffusion.

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The part of oxygen that is produced by the plant in photosynthesis is utilized by the plant for breathing and rest of the oxygen is given out by plants through stomata which we use for breathing.