Question

which of the following processes causes most of the carbon dioxide from the blood to

passive transport using carrier proteins

diffusion down a concentration gradient

conversion to carbon monoxide

active transport using energy

Explanation:

Carbon dioxide moves from the blood to the alveoli (in the lungs) by simple diffusion. Diffusion is the movement of molecules from an area of higher concentration to an area of lower concentration (down a concentration gradient). Carbon dioxide is more concentrated in the blood (due to cellular respiration in body cells producing it) than in the alveoli (which is refreshed with air that has lower \(CO_2\) levels during inhalation).

Passive transport using carrier proteins is typically for substances like glucose (facilitated diffusion). Conversion to carbon monoxide is not a normal physiological process for removing \(CO_2\) from the blood. Active transport requires energy (usually in the form of ATP) and is against a concentration gradient, which is not the case for \(CO_2\) removal from the blood.

Answer:

Diffusion down a concentration gradient