What determines the direction that carbon dioxide and oxygen molecules move would be the intracellular concentration of the substances.
Carbon dioxide and oxygen are only able to move across a plasma membrane by diffusion. Diffusion involves the movement of molecules from the region of higher concentration to the region of lower concentration.
Thus, if the concentration of carbon dioxide and oxygen is more in the cell than the surrounding medium, they will diffuse across the plasma membrane outside the cell.
On the contrary, if the intracellular concentration of carbon dioxide and oxygen is lower than that of the surrounding medium of the cell, both substances will diffuse across the membrane to the inside of the cell.
More on diffusion can be found here: https://brainly.com/question/24746577?referrer=searchResults
