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Slide 1

• PLASMA MEMBRANE - is a thin semi-permeable membrane that surrounds the cytoplasm of a cell
• FUNCTIONS:
•  protect the integrity of the interior of the cell by allowing certain substances into the cell, while keeping
• other substances out (selectively permeable)
•  serves as a base of attachment for the cytoskeleton in some organisms and the cell wall in others
•  serves to help support the cell and help maintain its shape
•  regulate cell growth through the
• balance of endocytosis
• and exocytosis
•  In endocytosis, lipids and
• proteins are removed from the
• cell membrane as substances
• are internalized
•  In exocytosis, vesicles containing lipids and proteins fuse with the cell membrane increasing cell size
•  Animal cells, plant cells, prokaryotic cells, and fungal cells have plasma membranes.
• Internal organelles are also encased by membranes
• STRUCTURAL COMPONENTS OF PLASMA MEMBRANE:
• A. CELL MEMBRANE LIPIDS
•  Phospholipids are lipid bilayer which is semi-permeable, allowing only certain molecules
• to diffuse across the membrane.
•  Cholesterol molecules are selectively dispersed between membrane phospholipids. This helps to
• keep cell membranes from becoming stiff by preventing phospholipids from being too closely packed
• together. Cholesterol is not found in the membranes of plant cells.
•  Glycolipids are located on cell membrane surfaces and have a carbohydrate sugar chain attached to
• them. They help the cell to recognize other cells of the body.
• B. CELL MEMBRANE PROTEINS
•  Peripheral membrane proteins are exterior to and connected to the membrane by interactions with
• other proteins.
•  Integral membrane proteins. Portions of these transmembrane proteins are exposed on both sides of
• the membrane.
•  Structural proteins help to give the cell support and shape