Substances that move into cells:
* Oxygen (O2): Cells need oxygen for respiration, the process of producing energy. Oxygen diffuses from the higher concentration in the surrounding environment into the lower concentration inside the cell.
* Nutrients: Cells require nutrients like glucose (sugar) and amino acids (building blocks for proteins) to function. These substances move from higher concentrations outside the cell to lower concentrations inside.
* Water (H2O): Cells need water for various processes, and it moves across the cell membrane from areas of high water concentration to areas of low concentration.
Substances that move out of cells:
* Carbon dioxide (CO2): A byproduct of respiration, carbon dioxide diffuses out of the cell and into the surrounding environment.
* Waste products: Cells produce waste products like urea and ammonia. These substances move from higher concentrations inside the cell to lower concentrations outside.
* Hormones: Cells can release hormones into the bloodstream, where they travel to other cells in the body.
Factors influencing diffusion:
* Concentration gradient: The difference in concentration between two areas. The steeper the gradient, the faster the diffusion.
* Membrane permeability: The ease with which a substance can cross the cell membrane. Some substances move easily, while others require special transport mechanisms.
* Temperature: Higher temperatures increase the rate of diffusion.
* Surface area: A larger surface area allows for faster diffusion.
It's important to note that while diffusion is a passive process that doesn't require energy, some substances require active transport, which involves energy expenditure, to move across cell membranes.
