Summary:
- The cell membrane is selectively permeable, allowing only certain substances to pass through.
- Diffusion is the movement of molecules from an area of high concentration to an area with a lower concentration.
- Active transport is when the cell uses energy to pull in or pump out certain molecules and ions.
- Vesicle transport is in which large molecules are moved across the membrane in bubble-like sacks that are made from pieces of the membrane.
- In this way, cell membranes help maintain a state of homeostasis within cells (and tissues, organs, and organ systems)