RESPIRATION IN ORGANISMS

 NOTES

1. Aerobic Respiration
When the breakdown of glucose occurs with the use of oxygen, it is called aerobic respiration. During aerobic respiration, glucose is completely broken down into carbon dioxide and water and energy is released. Aerobic respiration takes place in mitochondria.
It can be shown by the following equation:
Glucose(food) Oxygen−→−−−− Carbon dioxide + Water + Energy
Aerobic respiration is seen in most of the organisms such as humans (man), dogs, cats, lions, elephants, cows, buffaloes, goats, snakes, earthworms, frogs, fishes, etc.

2. Anaerobic Respiration
When a breakdown of glucose takes place without using oxygen, it is called anaerobic respiration. The glucose is not completely broken down into carbon dioxide and water. An intermediate compound is formed with the release of less amount of energy during this process. It can be shown as follows:
Glucose -----> Alcohol + Carbon dioxide + Energy
Yeasts such as Saccharomyces cerevisiae and certain bacteria carry out anaerobic respiration. These organisms that carry out respiration in the absence of oxygen are called anaerobes.

• anaerobic respiration may also occur in our muscles for a short time, due to temporary deficiency of oxygen. When we perform a heavy exercise like running, cycling, walking, weight lifting, etc., we require a large amount of energy. To meet the energy requirement our muscle cells perform anaerobically. respiration. During this process, the glucose or food in the muscle cells is partially broken down in the absence of oxygen to form lactic acid and some extra energy is released.

Breathing
It is the process in which air rich in oxygen is taken inside and air rich in CO2 is given out, with the help of respiratory organs. Thus, breathing involves two steps which take place alternately.

• Inhalation: Taking in of air rich in oxygen into our body is called inhalation.
• Exhalation: Giving out air rich in carbon dioxide from our body to the external environment is called exhalation.

****The number of times a person breathes in a minute is termed as breathing rate. An adult human being can inhale and exhale 15-18 times in a minute. It is the average breathing rate of an adult human being.

Percentage of O2	Percentage of CO2
Inhaled air	21%	0.04%
Exhaled air	16.4%	4.4%

Exercise Questions

1. Why does an athlete breathe faster and deeper than usual after finishing the race?

Solution:

Athletes need a lot of energy during the race, and for the release of energy, they need a lot of Oxygen; hence they breathe faster than usual after finishing the race.

2. List the similarities and differences between aerobic and anaerobic respiration.

Solution:

Similarities: 

1. In both kinds of respiration, food particles are broken down to release energy
2. Both occurs inside the cells
3. Both supply by-products

Differences

Aerobic respiration	Anaerobic respiration
Takes place in the presence of Oxygen	Takes place in the absence of Oxygen
End products are CO2 and H2O	End products are CO2 and alcohol
Produces a large amount of energy	The energy released is less when compared to aerobic respiration
It occurs in most plants and animals	Occurs in yeast and some bacteria

3. Why do we often sneeze when we inhale a lot of dust-laden air?

Solution:

When we inhale dust-laden air, the dust irritates the nose; as a reflexive action, dust is thrown out through sneezing.

4. Take three test-tubes. Fill ¾th of each with water. Label them A, B and C. Keep a snail in test-tube A, a water plant in test-tube B and in C, keep snail and plant both. Which test-tube would have the highest concentration of CO2 ?

Solution:

Test tube A will have the highest concentration of CO2 because test-tube A will have Snail which expels out CO2 into the tube. Since a plant is present in both test tubes B and C, the plant will inhale CO2 to decrease CO2 concentration. Thus, there will be less concentration of CO2 in these tubes.

5. Tick the correct answer:

(a) In cockroaches, air enters the body through

(i) lungs (ii) gills (iii) spiracles (iv) skin

(b) During heavy exercise, we get cramps in the legs due to the accumulation of

(i) carbon dioxide (ii) lactic acid (iii) alcohol (iv) water

(c) Normal range of breathing rate per minute in an average adult person at rest is:

(i) 9–12 (ii) 15–18 (iii) 21–24 (iv) 30–33

(d) During exhalation, the ribs

(i) move outwards (ii) move downwards (iii) move upwards (iv) do not move at all

Solution:

a) (iii) spiracles

b) (ii) lactic acid

c) (ii) 15–18

d) (ii) move downwards

6. Match the items in Column I with those in Column II:

Column I	Column II
(a) Yeast	(i) Earthworm
(b) Diaphragm	(ii) Gills
(c) Skin	(iii) Alcohol
(d) Leaves	(iv) Chest cavity
(e) Fish	(v) Stomata
(f) Frog	(vi) Lungs and skin
	(vii) Trachae

Solution:

Column I	Column II
(a) Yeast	(iii) Alcohol
(b) Diaphragm	(iv) Chest cavity
(c) Skin	(i) Earthworm
(d) Leaves	(v) Stomata
(e) Fish	(ii) Gills
(f) Frog	(vi) Lungs and skin

7. Mark ‘T’ if the statement is true and ‘F’ if it is false:

(i) During heavy exercise the breathing rate of a person slows down. (T/F)

(ii) Plants carry out photosynthesis only during the day and respiration only at night. (T/F)

(iii) Frogs breathe through their skins as well as their lungs. (T/F)

(iv) The fishes have lungs for respiration. (T/F)

(v) The size of the chest cavity increases during inhalation. (T/F)

Solution:

i) False

ii) False

iii) True

iv) False

v) True

8. Given below is a square of letters in which are hidden different words related to respiration in organisms. These words may be present in any direction — upwards, downwards, or along the diagonals. Find the words for your respiratory system. Clues about those words are given below the square.

(i) The air tubes of insects

(ii) Skeletal structures surrounding chest cavity

(iii) Muscular floor of chest cavity

(iv) Tiny pores on the surface of leaf

(v) Small openings on the sides of the body of an insect

(vi) The respiratory organs of human beings

(vii) The openings through which we inhale

(viii) An anaerobic organism

(ix) An organism with tracheal system

Solution:

(i) Trachea

(ii) Ribs

(iii) Diaphragm

(iv) Stomata

(v) Spiracles

(vi) Lungs

(vii) Nostrils

(viii) Yeast

(ix) Ant

9. The mountaineers carry oxygen with them because:

(a) At an altitude of more than 5 km there is no air.

(b) The amount of air available to a person is less than that available on the ground.

(c) The temperature of air is higher than that on the ground.

(d) The pressure of air is higher than that on the ground.

Solution:

The answer is (b). The amount of air available to a person is less than that available on the ground.