The document discusses the structure and function of the plasma membrane and the movement of substances across it. The plasma membrane is a selectively permeable phospholipid bilayer that controls the movement of substances into and out of cells. Substances can move passively via simple diffusion, facilitated diffusion, or osmosis. Active transport requires energy and transports molecules against a concentration gradient using carrier proteins.

1. movement of substances across the plasma membrane

2. what are the substances needed by the cells? how the needed substances move into the cells?

5. plasma membrane structure

18. Through phospholipids layer: Non polar molecules = Oxygen. Carbon dioxide, water , lipid soluble molecules By pore – proteins : water soluble molecules and ions By carrier- proteins and energy : ions. By carrier- proteins : glucose, amino acids.

20. Diffusion The net movement of a substance (molecules) down a concentration gradient from an area of high con centration to an area of low concentration .

23. Example:

37. Cell membranes are completely permeable to water, therefore, the environment the cell is exposed to can have a dramatic effect on the cell.

52. application of osmosis Why the use of excess fertilizer caused wilting in plant?

53. Explain these preservation process