Question

A cell membrane is permeable to both oxygen and carbon dioxide molecules. Initially, in what direction will the oxygen and carbon dioxide molecules most likely move?

A. O2 will enter the cell, carbon will exit.
B. Oxygen will exit the cell, and carbon will enter.
C. Both will enter.
D. Both will exit.

Answer 1

Oxygen (O2) and carbon dioxide (CO2) move across the cell membrane by simple diffusion, with O2 entering the cell due to lower internal concentration, and CO2 exiting because of higher internal concentration, making option A the correct answer.

Step-by-step explanation:

The direction in which oxygen (O2) and carbon dioxide (CO2) molecules will move across a cell membrane can be predicted based on the concentration of these gases inside and outside of the cell. As cells consume O2 rapidly for metabolism, its concentration tends to be lower inside the cell than outside, which will cause O2 to diffuse into the cell. Conversely, CO2 is produced as a byproduct of metabolism, leading to a higher concentration inside the cell than outside, which results in CO2 diffusing out of the cell. This process is known as simple diffusion, a type of passive transport where molecules move from an area of higher concentration to an area of lower concentration without the need for cellular energy.

Given this information, the initial direction of molecule movement would be: A. O2 will enter the cell, carbon dioxide will exit.