Cell Membranes by Darell

A cell membrane is a structure that surrounds the cell and protects it. All cells have a membrane, they have to have them to live. It offers protection, it is a filter, and holds everything together. Without a cell membrane the cell would most likely get a disease or get sick and die.

                                                                                                                              

The cell membrane can have a selectively permeable membrane in which it only lets water and nutrients into the cell and keep harmful molecules out. This diagram shows how the membrane lets the water and nutrients in and out of the cell but keeping the rest out.

For molecules that the cell wants but its too large to go through the membrane it goes through a process called endocytosis. Endocytosis is when a cell needs a large molecule but has too surround it and absorb it into the cell instead of it entering through the membrane.

Diffusion is when the molecules move in and out of the cell from area with high concentration to low concentration until they reach equilibrium.