How does something as thin as a cell wall or membrane protect a cell?
Among the most important parts of a cell are its borders, which separate the cell from its surroundings. All cells are surrounded by a thin, flexible barrier known as the cell membrane. Many cells also produce a strong supporting layer around the membrane known as a cell wall.
The cell membrane is not like a like a ziploc bag. It is constructed so that certain small molecules, like water, can move easily in and out of the cell. Other larger molecules have special protein channels that allow them entrance. Special pumps control the amounts of some substances.
*Active Transport * Requires the cell to use energy (ATP) * From low concentration to high concentration (Uphill) Osmosis Diffusion Facilitated Diffusion Endocytosis Exocytosis Pinocytosis Phagocytosis Transport Pumps *Passive *No energy (ATP) required *From high concentration to low concentration ( Downhill)
Exocytosis Active and Passive Transport Pinocytosis