Difficulty: Medium

Average Score: 58%

What process causes most of the carbon dioxide from the blood to move into alveoli?

Rationale

Diffusion down a concentration gradient is the process that causes most of the carbon dioxide from the blood to move into alveoli.

This process is how gases exchange in the lungs, with carbon dioxide (CO2) moving from an area of high concentration (the blood) to an area of lower concentration (alveoli). This passive process does not require energy or carrier proteins.

A (Active transport) YOUR ANSWER

Active transport is not the correct process because it involves moving molecules across a cell membrane from an area of lower concentration to an area of higher concentration. This requires energy, typically from ATP. However, the movement of carbon dioxide from blood to alveoli is a passive process, moving from high to low concentration, and thus does not require energy.

B (Diffusion down a concentration gradient) CORRECT

The diffusion of carbon dioxide from the blood to the alveoli occurs due to the difference in concentration between the two zones. This process is called diffusion down a concentration gradient. It's a passive process, not requiring energy or carrier proteins.

C (Passive transport using carrier proteins) YOUR ANSWER

Passive transport using carrier proteins is not the correct process because the movement of carbon dioxide from the blood to the alveoli does not require carrier proteins. Carbon dioxide is small and nonpolar, allowing it to easily diffuse across the alveolar and capillary membranes without the need for carrier proteins.

D (Conversion to carbon monoxide) YOUR ANSWER

Conversion to carbon monoxide is not the correct process because CO2 is not converted into CO in the body. Instead, CO2 is transported directly from the blood to the lungs for expulsion during exhalation.

Conclusion

The process that causes most of the carbon dioxide from the blood to move into the alveoli is diffusion down a concentration gradient. It is a passive process, which does not require energy or carrier proteins. Other options involving active transport, passive transport using carrier proteins, or conversion to carbon monoxide do not accurately describe this process.

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