Question

How does co2 or O2 move across the cell membrane

Answer 1

Hey,
Some substances like O2 and CO2 move accross the cell by the process of diffusion.
CO2 accumulates inside the cell, where concentration is low, than the outer region.
Thus, Co2 moves out of the cell by the process of diffusion from lower region of concentration to region where it is higher.
Water or O2 also follows the laws of diffusion. The movement of water molecules of region of lower concentration to region where it is higher is called osmosis.
Hope you got it ^_^

Answer 2

Through osmosis ...................