Which one of the following can respire in the absence of oxygen ?

The process of migration of chloride ions from plasma to RBC and carbonate ions from RBC to plasma is

Solution

During the transport of CO₂ through the blood, bicarbonate ions diffuse out of RBCs while chloride ions from plasma enter the RBCs to maintain ionic equilibrium. This is called chloride shift.

The exchange of gases in the alveoli of the lungs takes place by

Solution

Gaseous exchange between blood (dissolved phase) and alveolar air (gaseous phase) across respiratory membrane occurs by simple diffusion. Obviously, it depends upon the concentration gradient (= partial pressure) of the concerned gases in blood and alveolar air.

In alveoli of the lungs, the air at the site of gas exchange, is separated from the blood by

alveolar epithelium only
alveolar epithelium and capillary endothelium
alveolar epithelium, capillary endothelium and tunica adventitia
alveolar epithelium, capillary endothelium, a thin layerof tunica media and tunica adventitia

Solution

Alveoli are the site of the respiratory exchange of gases.Oxygen from the alveolar air diffuses through the alveolar epithelium and the capillary endothelium into the capillary blood and carbon dioxide diffuses in the opposite direction.

The quantity 1500 ml in the respiratory volumes of a normal human adult refers to

Solution

The total volume of air that can be expelled from the lungs after maximum inspiration and then expiring to the maximum is known as the vital capacity. The volume of air that remains inside lungs at the end of maximum forceful expiration is the residual volume. Expiratory reserve volume is the maximum extra volume of air that can be expired by forceful expiration after a normal tidal expiration. Total lung capacity is the maximum volume of air that can be contained in the lungs after maximum inspiration.

The volume of air that remains in the lungs after normal expiration is

The carbon dioxide is transported via blood to lungs as

Solution

Carbon dioxide is transported via blood to lungs mostly as carbaminohaemoglobin and carbonic acid. It is released in lungs in exchange with oxygen.

Although much CO₂ is carried in blood, yet blood does not become acidic, because

Solution

CO₂ enters RBC and reacts with water to form carbonic acid. Carbonic acid dissociates to form bicarbonate and hydrogen ions. Some bicarbonate ions are transported in erythrocytes while some diffuse into the blood plasma.Exit of bicarbonate ions change the ionic balance between the plasma and erythrocytes. To restore this balance chloride ions diffuse from plasma into erythrocytes. Due to this the pH of blood is maintained.

Air is breathed through

Solution

The pathway of inhaled air is - Nostrils - pharynx (common passage for food & air) - larynx (voice box) - trachea (the wind pipe) - bronchi (2 for each side lungs) - bronchioles (give arise to alveolar ducts) - alveoli (the exchange site for gases in the form of small sacs or pouches).

Carbon dioxide is transported from tissues to respiratory surface by

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