Substances like CO2 and water move in and out of cells primarily through diffusion and osmosis, respectively, across the selectively permeable cell membrane.
Movement of CO2
CO2 is produced inside the cell during cellular respiration and is present at a higher concentration inside the cell than outside. It moves out of the cell by diffusion , which is the movement of molecules from an area of higher concentration to an area of lower concentration. This process does not require energy and occurs directly through the cell membrane because CO2 is small and nonpolar, allowing it to pass freely.
Movement of Water
Water moves in and out of the cell by osmosis , a specialized type of diffusion where water moves through a semi-permeable membrane from a region of higher water concentration (or lower solute concentration) to a region of lower water concentration (or higher solute concentration). The cell membrane allows water to pass while blocking many solutes. Osmosis balances the internal and external water concentrations, affecting cell volume: water entering the cell causes it to swell, while water leaving causes it to shrink. Water movement is also facilitated by protein channels called aquaporins, which increase the rate of water flow.
Summary
- CO2 moves out of the cell by diffusion following its concentration gradient.
- Water moves in and out by osmosis, dependent on solute concentrations inside and outside the cell.
- The cell membrane’s selective permeability controls these movements without needing energy.
This coordination of diffusion and osmosis maintains cell homeostasis and proper cellular function.
