1. Lecturer: SALMA ALRDAHE Cell Membrane4th lab

2. Cell Membrane The cell membrane or plasma membrane is a biological membrane that separates the interior of all cells from the outside environment

4. Cell membrane under microscope

5. Cell membrane under microscope

6. Singer and Nicolson model of Cell membrane

7. Functions of Cell Membrane • It surrounds the cytoplasm of animal and plant cells, physically separating the intracellularcomponents from the extracellular environment. • The membrane is selectively permeable and able to regulate what enters and exits the cell. • The movement of substances across the membrane can be: • either "passive", occurring without the input of cellular energy, • or active, requiring the cell to expend energy in transporting it.

8. Cell membrane employs a number of transport mechanisms: • 1. Passive diffusion and osmosis: Some substances (small molecules, ions) such as (CO2), (O2), and water, can move across the plasma membrane by diffusion • (passive transport process). • 2. Transmembrane protein channels and transporters: Nutrients, such as sugars or amino acids, must enter the cell, and certain products of metabolism must leave the cell.

9. Cell membrane employs a number of transport mechanisms: • 3. Endocytosis: Endocytosis is the process in which cells absorb molecules by engulfing them. • Endocytosis requires energy (active transport). • 4. Exocytosis: the membrane of a vesicle can be fused with the plasma membrane, extruding its contents to the surrounding medium. • Exocytosis occurs to: • remove undigested residues of substances • secrete substances such as hormones and enzymes.