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# Breathing and Exchange of Gases

#### Multiple Choice Questions

1.

Which of the following products are obtained by anaerobic respiration from yeast?

• Alcohols

• CO2

• Beer and Wine

• All of the above

D.

All of the above

Anaerobic Respiration is a process in which organisms produce energy in absence of oxygen. During anaerobic respiration, pyruvic acid forms ethyl alcohol (C2H5OH) and CO2. This process is known as fermentation.

2.

At high altitude, RBC's of human blood will

• increase in number

• decrease in number

• decrease in size

• increase in size

A.

increase in number

At altitude the partial pressure of the oxygen decreases in atmosphere so there is less oxygen available to carry out respiration. In order to compensate the cellular oxygen demand, the body increases the amount of RBC present to trap as many oxygen molecules as possible.

3.

Assertion : Severe Acute Respiratory Syndrome (SARS) originated in China.

Reason : China is the most populated country of the world.

• If both Assertion and Reason are true and the reason is the correct explanation of the assertion

• If both Assertion and Reason are true but the reason is not the correct explanation of the assertion

• If Assertion is true statement but Reason is false

• If both Assertion and Reason are false statements

B.

If both Assertion and Reason are true but the reason is not the correct explanation of the assertion

SARS or Severe Acute Respiratory Syndrome is a severe acute type of 'atypical pneumonia'. It is caused by metapneumo virus (a type of corona virus). It was first reported by WHO in China (Beijing, Guangdong, HongKong, Taiwan etc.) Though China is the most populated country of the world, it is not directly responsible for the origin of SARS. The killer pneumonia virus is responsible for SARS origin.

4.

What will be the number of Calvin cycles to generate one molecule of hexose?

• 4

• 6

• 8

• 9

B.

6

Six turns of the Calvin cycle result in the production of one molecule of glucose.

5.

The vital capacity of lungs is equal to

• 4000 ml

• 5000 ml

• 6000 ml

• 7000 ml

B.

5000 ml

The vital capacity is the maximum amount of air that can be expelled from lungs by forced exhalation after a forced inhalation. It is equal to the sum of tidal volume (TV), inspiratory reserve volume (IRV) and expiratory reserve volume (ERV).
VC= TV+ IRV+ ERV
= 500 + 3000 + 1100
=4600 ml

6.

During anaerobic conditions, the rate of glycolysis increases, is called

• compensation point

• extinction point

• Warburg effect

• Pasteur effect

D.

Pasteur effect

The rate of glycolysis increases because in anaerobic respiration the rate of ATP production is 2ATP per glucose mol. while in aerobic it is 38ATP per glucose so to compensate the increased ATP demand the rate of glycolysis increases.

7.

The majority of carbon dioxide produced by our body cells is transported to the lungs

• dissolved in the blood

• as bircarbonates

• as carbonates

• as carbonates

B.

as bircarbonates

In our body, the blood transports the CO2 in three ways:
(i) Majority of carbon dioxide produced (70%) in our cells is transported in the form of bicarbonates. In this way first, the CO2 that dissolves in blood plasma reacts with water forming carbonic acid which dissociates into hydrogen and bicarbonate ions.

(ii) About 7% of all the CO2 of transported by blood from tissues to the lungs is in dissolved state in plasma.
(iii) About 23% of CO2, collected from cells through tissue fluids, is transported by blood in the form of carbamino compound, carbamino-haemoglobin (CO2HHb).

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8.

People living at sea level have around 5 million RBC per cubic millimeter of their blood whereas those living at an altitude of 5400 metres have around 8 million. This is because at high altitude:

• people get pollution-free air to breathe and more oxygen is available

• atmospheric O2 level is less and hence more RBCs are needed to absorb the required amount of O2 to survive

• there is more UV radiation which enhances RBC production

• there is more UV radiation which enhances RBC production

B.

atmospheric O2 level is less and hence more RBCs are needed to absorb the required amount of O2 to survive

At high altitudes, the atmospheric O2 level is less and hence, more RBCs are needed to absorb the required amount of O2 to survive. That is why, the people living at sea level have around 5 million RBC/mm3 of their blood whereas those living at an altitude of 5400 meters have around 8 million RBC/mm3 of their blood.

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9.

The respiratory centre in the brain is stimulated by

• CO2 concentration in venous blood

• O2 concentration in artery blood

• CO2 concentration in artery blood

• O2 concentration in venous blood

C.

CO2 concentration in artery blood

Respiratory centre controls rhe rate of respiration. It is located in medulla oblongata and pons. It has the following components:

(i) Inspiratory area

(ii) Pneumotaxic area

(iii) Expiratory area

(iv) Chemosensitive area

Chemoreceptors located on carotid and aortic bodies are sensitive to carbon dioxide levels in arterial blood. They send information to respiratory centre. Oxygen does not have a significant direct effect on the respiratory centre of the brain.

10.

In respiration from 180g of glucose which of the following is formed?

• 264gm CO2 + 190gm H2O + 391 Kcal

• 264gm CO2 + 108gm H2O + 686 Kcal

• 390gm CO2+ 108gm H2O + 686 Kcal

• 390gm CO2 + 264gm H2O + 391 Kcal

B.

264gm CO2 + 108gm H2O + 686 Kcal

In respiration from 180 gm of glucose, 264 gm CO2 + 108 gm H2O + 686 Kcal energy is formed.

C6H12O6 + 6O2 $\to$6CO2 +6H2O + 686 Kcal.

Atomic weight of C = 12; H = 1 and O = 16

C6H12O6 = (12 x 6 + 12 x 1 + 16 x 6) = 180 gm

6CO2      = 6 (12 + 16 x 2) = 264 gm

6H2O       = 6 (2 x 1 +16) = 108 gm

Therefore, 1 molecular or 180 gm of glucose, through respiration, 264 gm CO2, 108 gm H2O and 686 Kcal energy are formed.