FREE NEET Biology Practice MCQ Test: Breathing And Exchange Of Gases Exercise 2 Questions Answers With Detailed Explanations [PDF]

Answer: (a)

Buffer is a solution that resists change in pH when an acid or alkali is added or when the solution is diluted. Acidic buffers consists of a weak acid with a salt of the acid. The salt provides the negative ion A, which is the conjugate base of the acid HA. An example is carbonic acid and sodium hydrogen carbonate in which molecules H₂CO₃ and ions HCO₃^– are present. About 70% of C$O_2$ released combines with water in the RBCs to form carbonic acid. Carbonic acid dissociates into bicarbonate and hydrogen ions. Addition of H + ions would make the blood acidic. However, most of the hydrogen ions are neutralized by combination with Hb, forming acid haemoglobin. This reduces the acidity of the blood and also releases additional O₂

$HbO_2^{-}  +  H^{-}  ⇌ HHb  +  O^2$

Answer: (d)

Answer: (b)

Spleen receives only oxygenated blood from the heart through splenic artery. The liver receives a blood supply from two sources. The first is the hepatic artery which delivers oxygenated blood from the general circulation. The second is the hepatic portal vein delivering deoxygenated blood from the small intestine containing nutrients. The blood flows through the liver tissue to the hepatic cells where many metabolic functions take place. The blood drains out of the liver via the hepatic vein. Gill and Lung receive deoxygenated blood as these are the organs where oxygenation of blood takes place.

Answer: (d)

Answer: (b)

Answer: (a)

Answer: (d)

Answer: (c)

Answer: (b)

The urge to inhale in humans results from rising $pCO_{2}$ . It is the increase of blood levels of carbon dioxide ($PCO_{2}$) that causes the urge to breathe in, not a lack of dissolved oxygen ($PO_{2}$).

Answer: (d)

Answer: (d)

Answer: (a)

Alveoli are very thin, irregular walled bag like structures for gaseous exchange. Tracheae bronchi and bronchioles are supported by incomplete cartilaginous rings. Double layered pleural membrane surrounds the lungs with pleural fluid between them. It reduces friction on the lung surface.

Answer: (c)

Chemoreceptors in the medulla get stimulated by increase in $CO_{2}$ concentration in the blood of arteries. Decrease in $O_{2}$ concentration has no significant effect on chemoreceptors.

Answer: (b)

Answer: (c)

Answer: (a)

Answer: (b)

Answer: (a)

Answer: (b)

At the tissue site where partial pressure of $CO_2$ is high due to catabolism, $CO_2$ diffuses into blood (RBCs and plasma) and forms $HCO^{–}_{2}$ and $H^{+}$. At the alveolar site where p$CO_2$ is low, the reaction proceeds in the opposite direction leading to the formation of $CO_2$ and $H_2$O. Thus, $CO_2$ trapped as bicarbonate at the tissue level and transported to the alveoli is released out as $CO_2$.

Answer: (a)

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.