Q: Which of the following equations correctly represents the reaction catalyzed by carbonic anhydrase in erythrocytes?

$$ \mathrm{CO_2 + H_2O \xrightleftharpoons[\text{carbonic anhydrase}]{} H_2CO_3} $$

Question 1

Which of the following best explains why respiratory pigments are necessary for animals with high metabolic rates?

Accepted Answer

Respiratory pigments increase the solubility of O2 in water, allowing more O2 to be transported in the blood.

Question 2

Refer to the first image. What is the main reason for the net diffusion of O2 from alveolar air spaces into the blood in alveolar capillaries?

Accepted Answer

The partial pressure of O2 ($$P_{O_2$}) is $$higher in the alveolar air spaces than in the blood entering the alveolar capillaries.

Question 3

Hemoglobin can bind up to four molecules of O2. What structural feature allows this?

Accepted Answer

Each hemoglobin molecule has four subunits, each with a heme group containing an iron atom that binds one O2 molecule.

Question 4

What is the Bohr shift, and how does it facilitate O2 delivery to active tissues?

Accepted Answer

A decrease in pH (from increased CO2) lowers hemoglobin's affinity for O2, causing more O2 to be released where it is needed most.

Question 5

Which of the following equations correctly represents the reaction catalyzed by carbonic anhydrase in erythrocytes?

Accepted Answer

$$ \mathrm{CO_2 + H_2O \xrightleftharpoons[	ext{carbonic anhydrase}]{} H_2CO_3} $$

Question 6

Why do diving mammals like the Weddell seal have a greater capacity for underwater endurance compared to humans?

Accepted Answer

They have a higher blood volume per kilogram and more myoglobin in their muscles, allowing greater O2 storage.

Question 7

If a patient is breathing very rapidly, why might a doctor administer bicarbonate ($$\mathrm{$$HCO_3$$^-}$$)?

Accepted Answer

To buffer the blood and prevent a dangerous rise in pH due to excessive loss of CO2.

Question 8

Which of the following best describes the cooperative binding of O2 by hemoglobin?

Accepted Answer

Binding of one O2 molecule increases the affinity of the remaining subunits for O2.

Question 9

During intense exercise, what happens to the partial pressure of O2 ($$P_{O_2$}) in $$the tissues, and how does this affect O2 unloading from hemoglobin?

Accepted Answer

$$P_{O_2$}$$ decreases, causing hemoglobin to unload more O2 due to the steep part of the dissociation curve.

Question 10

Which of the following is the primary way most CO2 is transported from tissues to the lungs?

Accepted Answer

As bicarbonate ions ($$\mathrm{$$HCO_3$$^-}) $$dissolved in plasma.

Question 11

What would happen to the partial pressures of O2 and CO2 in the alveoli if you consciously forced more air out of your lungs with each exhalation?

Accepted Answer

Alveolar $$P_{O_2$}$$ would increase and $$P_{CO_2$}$$ would decrease, enhancing gas exchange.

Question 12

Which adaptation allows diving mammals to conserve O2 during long dives?

Accepted Answer

They reduce heart rate and restrict blood flow to non-essential tissues.

Question 13

Which of the following best explains why hemoglobin is an effective buffer in blood?

Accepted Answer

Hemoglobin binds H+ ions produced from carbonic acid dissociation, minimizing changes in pH.

Question 14

Which of the following is a correct sequence for the movement of O2 from the atmosphere to body tissues in humans?

Accepted Answer

Alveoli → blood in pulmonary capillaries → heart → systemic capillaries → body tissues

Question 15

Which of the following would most likely occur if hemoglobin did not exhibit cooperative binding?

Accepted Answer

Hemoglobin would be less efficient at loading and unloading O2, especially in tissues with varying $$P_{O_2$}.$$

Adaptations for Gas Exchange: Respiratory Pigments and Physiological Strategies

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