Question

complete the paragraph.
at the start of the video, there is a higher concentration of carbon dioxide molecules
inside the cell than outside the cell. as carbon dioxide molecules move by simple
diffusion, molecules cross the cell membrane in one direction.
molecules move from inside the cell to the outside, until the concentration outside the
cell is the concentration inside the cell. overall, the video shows
that the net movement of carbon dioxide is its concentration gradient.

Explanation:

• For the first blank: In simple diffusion, molecules move from an area of higher concentration to lower. Since initially there's higher \(CO_2\) inside the cell, this is correct.
• For the second blank: In simple diffusion, molecules move down the concentration gradient (from higher to lower). So they move in one direction (out of the cell here as inside has higher initial concentration).
• For the third blank: Diffusion continues until equilibrium is reached. So the concentration outside becomes equal to that inside.
• For the fourth blank: Net movement in simple diffusion is down (along) the concentration gradient.

Answer:

• As carbon dioxide molecules move by simple diffusion, molecules cross the cell membrane in one direction (down the concentration gradient).
• Molecules move from inside the cell to the outside, until the concentration outside the cell is equal to the concentration inside the cell.
• Overall, the video shows that the net movement of carbon dioxide is down (along) its concentration gradient.