NEET MCQs Practice on Breathing and Exchange of Gases Class-XI Biology, Free unlimited practice on Breathing and Exchange of Gases Class-XI Biology Mcqs

Question 81 of 100

📘 CLASS XI

Which environmental factors in tissues favor dissociation of oxygen from oxyhaemoglobin?

I. Low pO₂
II. High pCO₂
III. High H⁺ concentration
IV. Higher temperature

Explanation: All four tissue conditions, namely low pO₂, high pCO₂, high H⁺ concentration, and higher temperature, promote the release of oxygen from oxyhaemoglobin.

Question 82 of 100

📘 CLASS XI

Under normal physiological conditions, how much oxygen is delivered to tissues by 100 mL of oxygenated blood?

I. Around 5 mL of O₂.
II. Around 4 mL of O₂.
III. Around 15 mL of O₂.
IV. Around 20 mL of O₂.

Explanation: Statement I is correct. Every 100 mL of oxygenated blood delivers approximately 5 mL of oxygen to tissues under normal physiological conditions.

Question 83 of 100

📘 CLASS XI

Consider the transport modes of carbon dioxide in human blood:

I. 20-25 per cent is carried by haemoglobin as carbamino-haemoglobin.
II. About 70 per cent is carried as bicarbonate (HCO₃^-).
III. About 7 per cent is carried in dissolved state through plasma.
IV. 97 per cent is carried bound to red blood cell iron centres.

Explanation: Statements I, II, and III are correct. Carbon dioxide is transported mainly as bicarbonate, partly as carbamino-haemoglobin, and a small amount in dissolved form. Statement IV is incorrect.

Question 84 of 100

📘 CLASS XI

Analyze the binding of carbon dioxide to haemoglobin:

I. CO₂ binds to haemoglobin as carbamino-haemoglobin.
II. Binding is related to partial pressure of CO₂ (pCO₂).
III. pO₂ is a major factor affecting this binding.
IV. High pCO₂ and low pO₂ in tissues favor more CO₂ binding.

Explanation: All four statements are correct. Carbon dioxide binds to haemoglobin as carbamino-haemoglobin. Its binding depends mainly on pCO₂ and is also influenced by pO₂; high pCO₂ and low pO₂ in tissues promote this binding.

Question 85 of 100

📘 CLASS XI

Consider the enzyme Carbonic Anhydrase:

I. RBCs contain a very high concentration of carbonic anhydrase.
II. Minute quantities of carbonic anhydrase are present in plasma.
III. Facilitates the reversible reaction: CO₂ + H₂O ⇌ H₂CO₃ ⇌ HCO₃^- + H⁺.
IV. Absent in RBCs and found exclusively in gastric mucosal glands.

Explanation: Statements I, II, and III are correct. Carbonic anhydrase is abundant in RBCs, present in small amounts in plasma, and catalyzes the reversible hydration of carbon dioxide. Statement IV is incorrect.

Question 86 of 100

📘 CLASS XI

Examine the direction of carbonic anhydrase reaction at tissue vs alveolar sites:

I. At tissue site (high pCO₂), CO₂ diffuses into blood and forms HCO₃^- and H⁺.
II. At alveolar site (low pCO₂), reaction proceeds in opposite direction forming CO₂ and H₂O.
III. CO₂ trapped as bicarbonate at tissues is released out as CO₂ at alveoli.
IV. Reaction proceeds unidirectionally at all body sites regardless of pCO₂.

Explanation: Statements I, II, and III are correct. High tissue pCO₂ drives bicarbonate formation, whereas low alveolar pCO₂ reverses the reaction to produce CO₂ gas for expiration. Statement IV is incorrect because the reaction is reversible and governed by pCO₂.

Question 87 of 100

📘 CLASS XI

Under normal physiological conditions, how much carbon dioxide is delivered to alveoli by 100 mL of deoxygenated blood?

I. Approximately 4 mL of CO₂.
II. Approximately 5 mL of CO₂.
III. Approximately 15 mL of CO₂.
IV. Approximately 20 mL of CO₂.

Explanation: Statement I is correct. Every 100 mL of deoxygenated blood delivers approximately 4 mL of CO₂ to the alveoli.

Question 88 of 100

📘 CLASS XI

Consider the Respiratory Rhythm Centre:

I. Located in the medulla region of the brain.
II. Primarily responsible for regulation of respiratory rhythm.
III. Located in the cerebellum.
IV. Located in the spinal cord dorsal horn.

Explanation: Statements I and II are correct. A specialized center in the medulla region called the respiratory rhythm center is primarily responsible for regulating respiratory rhythm. Statements III and IV are incorrect location claims.

Question 89 of 100

📘 CLASS XI

Analyze the Pneumotaxic Centre in the human brain:

I. Located in the pons region of the brain.
II. Can moderate the functions of the respiratory rhythm centre.
III. Neural signals from this centre can reduce the duration of inspiration.
IV. Can alter the respiratory rate.

Explanation: All four statements are correct. The pneumotaxic center in the pons moderates the respiratory rhythm center, reducing inspiration duration and thereby altering respiratory rate.

Question 90 of 100

📘 CLASS XI

Regarding the Chemosensitive Area in the brain, consider the statements:

I. Situated adjacent to the rhythm centre.
II. Highly sensitive to CO₂ and hydrogen ions (H⁺).
III. Activation of this centre signals rhythm centre to make necessary adjustments to eliminate CO₂ and H⁺.
IV. Highly sensitive to changes in nitrogen gas concentrations.

Explanation: Statements I, II, and III are correct. The chemosensitive area adjacent to the rhythm center senses increased CO₂ and H⁺ to signal the rhythm center for necessary respiratory adjustments. Statement IV is incorrect because it responds to CO₂ and H⁺, not nitrogen.

Breathing and Exchange of Gases MCQs