Question

Which of the following is true at the arterial ends of the pulmonary capillaries?

A. Oxygen is released from hemoglobin.
B. Carbon dioxide diffuses into the blood.
C. Oxygen is taken up by red blood cells.
D. Blood pressure is higher than in the venous ends.

Answer 1

At the arterial ends of the pulmonary capillaries, Oxygen is taken up by red blood cells where it binds to the hemoglobin within, as part of external respiration, causing the oxygenation of blood that returns to the heart.

Step-by-step explanation:

The question asks about the events that occur at the ends of the pulmonary capillaries. The correct answer is C: Oxygen is taken up by red blood cells. This process is a part of external respiration, where deoxygenated blood carried by the pulmonary artery from the heart is oxygenated through the gas exchange that occurs in the lungs. Here, oxygen diffuses out of the alveoli and into the surrounding capillaries, binding to the protein hemoglobin within erythrocytes (red blood cells). Simultaneously, carbon dioxide diffuses from the blood into the alveoli to be exhaled. Therefore, at the arterial ends of the pulmonary capillaries, oxygen is taken up by red blood cells, which increases the oxygen saturation of the blood returning to the heart through the pulmonary veins.