14211507-014Attiya Bano

Functions of cell membrane

CELL MEMBRANECell membrane

The semipermeable membrane surrounding the cytoplasm of a cell.

CompositionIt is composed of four different types of molecules:

PhospholipidsCholesterol

ProteinsCarbohydrates

Con

structure

ConFunctions of Cell Membranes:1. Compartmentalization:The major function of cellular membranes is compartmentalization. As plasma mem branes they separate the cells from their external environment. As organelle coverings, they allow the cell organelles to maintain their identity, specific internal environment and functional individuality.

Con2. Transfer of material: The membranes allow the flow of materials and information between different organelles of the same cell as well as between one cell and another.3. Source of Organic connection: As plasmodesmata and gap junctions, the bio membranes provide organic connections between adjacent cells.

Con4. Selective per meability: Plasma membranes as well as other membranes of the organelles have selective per meability, that is, they allow only selected substances to pass inwardly . The membranes are impermeable to others.

others.

Con6. Reorganization centers: Plasma membrane possesses specific substances at its surface which function as rec ognition Centre and points of attachments7. As antigen specificity: Substances attached to cell membrane determine antigen specificity. Glycophorins present on the surface of erythrocytes function as antigen determinants. Histocompatibility antigens signify whether a foreign cell or tissue should be incorporated or rejected.

Cont8.As a hormone receptor: Cell membrane has receptors for certain hormones. The hormone combines with its particular receptors and either changes membrane permeability or activates enzyme adenylatecyclase to produce cyclic AMP from ATP. AMP then triggers a set of enzymes to perform a particular function.9. Center of many reaction: Cell membranes contain enzymes for performing certain reaction on their surface, e.g., ATP-ase (for ATP synthesis and release of energy from ATP), phosphatases, esterases etc.

con9. Perform active transport: Membranes have carrier proteins for active transport.

Con

11. Work as an electron transport chain: Certain cell membranes (e.g. plasma membrane in bacteria, thylakoid membranes of chloroplasts, inner mitochondrial membrane) possess electron transport systems.12. Endocytosis: Membrane enfolds are used for bulk intake of

materials by endocytosis