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

What is vital capacity of our lungs?

Which of the following match is correct?

Respiration is controlled by

Chemosensitive area of respiratory centre medulla is affected by

Oxygen binding to haemoglobin in blood is

1. directly proportional to the concentration of CO₂ in the medium
2. inversely proportional to the concentration of CO₂ in the medium
3. directly proportional to the concentration of CO in the medium
4. independent of the concentration of CO in the medium.

The figure shows a diagrammatic view of human respiratory system with labels A, B, C

and D. Select the option, which gives correct identification and main function and/or

characteristic.

1. A-trachea-long tube supported by complete cartilaginous rings for conducting

inspired air

2. 8-pleural membrane-surround ribs on both sides to provide cushion against rubbing

3. C-alveoli-thin walled vascular bag-like structures for exchange of gases

4. D-lower end of lungs-diaphragm pulls it down during inspiration

Approximately seventy percent of carbon dioxide absorbed by the blood will be

transported to the lungs

1. as bicarbonate ions

2. in the form of dissolved gas molecules

3. by binding to RBC

4. as carbamino-haemoglobin

Name the chronic respiratory disorder caused mainly by cigarette smoking

1. asthma

2. respiratofy acidosis

3. respiratory alkalosis

4. emphysema

The partial pressure of oxygen in the alveoli of the lungs is