A large proportion of oxygen is left unsused in the human blood even after its uptake by

the body tissues. This O₂

1. raises the P_CO2 of blood to 75 mm of Hg

2. is enough to keep oxyhaemoglobin

3. helps in relasing more O₂ to the epithelial tissues

4. acts as a reserve during muscular exercise

What is true about RBCs in humans?

1. They carry about 20-25 per cent of CO₂

2. They transport 99.5 per cent of O₂

3. They transport about 80 per cent oxygen only and the rest 20 per cent of it is

transported in dissolved state in blood plasma

4. They do not carry CO₂ at all

Which two of the following changes (1-4) usually tend to occur in the plain dwellers when

they move to high altitudes (3,500 m or more)?

(1) Increase in red blood cell size

(2) Increase in red blood cell production

(3) Increased breathing rate

(4) Increase in thrombocyte count Changes occurring are

1. (2) and (3)

2. (3) and (4)

3. (1) and (4)

4. (1) and (2)

What is vital capacity of our lungs?

1. Inspiratory reserve volume plus tidal volume

2. Total lung capacity minus expiratory reserve volume

3. Inspiratory reserve volume plus expiratory reserve volume

4. Total lung capacity minus residual volume

The haemoglobin of a human foetus

1. has a lower affinity for oxygen than that of the adult

2. its affinity for oxygen is the same as that of an adult

3. has only 2 protein subunits instead of 4

4. has a higher affinity for oxygen than that of an adult

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:

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

2. atmospheric O₂ level is less and hence more RBCs are needed to absorb the required

amount of O₂ to survive

3. there is more UV radiation which enhances RBC production

4. people eat more nutritive food, therefore more RBCs are formed

Which one of the following statements is incorrect ?

1. The residual air in lungs slightly decreases the efficiency of respiration in mammals

2. The presence of non-respiratory air sacs, increases the efficiency of respiration in birds

3. In insects, circulating body fluids serve to distribute oxygen to tissues

4. The principle of countercurrent flow facilitates efficient respiration in gills of fishes

In the tissues, high concentrations of carbon doxide

1. increases the affinity of haemoglobin to both oxygen and hydrogen

2. increases the affinity of haemoglobin to oxygen but decreases its affinity to hydrogen

3. decreases the affinity of haemoglobin to oxygen but increases its affinity to hydrogen

4. decreases the affinity of haemoglobin to both oxygen and hydrogen.

During winter a person died during sleep, the room was closed and a container with burnt

charcoal was found in the room. What may be the possible reason of his death?

1. non-availability of oxygen

2. Hb has more affinity to combine with carbon monoxide

3. Hb has more affinity to combine with nitrogen

4. combined effect of 1. and 3.

The respiratory centre in the brain is stimulated by

1. CO₂ concentration in venous blood

2. O₂ concentration in artery blood

3. CO₂ concentration in artery blood

4. O₂ concentration in venous blood.