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In this article, I am going to tell you all about plasma membranes. So without any due Lets Start!
Plasma Membrane:
The plasma membrane is the boundary of the Protoplasm. It is found in all Prokaryotic and Eukaryotic cells. The plasma membrane is also called a cell membrane or plasmalemma, or cell surface membrane. It controls the passage of materials into and out of the cell.
Composition of Plasma Membrane:
Chemically, the cell membrane consists of Proteins 60-80%, lipids 20-40%, and a small number of carbohydrates.
Structure of Plasma Membrane:
The fluid Mosaic Model of Plasma Membrane proposes that the membrane is a phospholipid bilayer in which protein molecules are either partially or wholly embedded. The proteins are scattered throughout the membrane in an irregular pattern like large icebergs float in the sea. The design of distribution of proteins can vary from membrane to membrane and also go on both surfaces of the membrane. The membrane is about 7nm thick.
The lipid part of the plasma membrane consists of two layers (bilayers) of phospholipids arranged in such a way that their hydrophobic ends face each other. In contrast, hydrophilic ends appear on the surface. The Steroids, Cholesterols are wedged into the phospholipid bilayer at some intervals. The plasma membrane is asymmetrical, i.e., their two-character and halves are not identical.
In general, most membrane proteins drift sideways in the fluid bilayer. The proteins within a membrane determine most of the functions. Carbohydrates are either attached to proteins (Glycoproteins) or lipids (Glycolipids) generally on the outer side of the membrane. Filaments of the Cytoskeleton are also present on the inner surface of the membrane. These support the plasma membrane.
Functions of plan membrane Lipids:
The lipid part of the plasma membrane controls the fluidity of the plasma membrane. When the concentration of unsaturated Fatty Acids in phospholipids becomes more incredible, the phospholipid bilayer becomes more fluid, making the cell membrane more flexible. The cholesterol helps to stabilize the lipid bilayer. It also restricts the entry and exit of polar molecules and ions.
The cell membrane's fluidity depends on its lipid components, including phospholipids, glycolipids, and cholesterol.
Functions of plasma membrane Proteins:
Many proteins are found in the plasma membrane, acting as a transport channel or carrier, enzymes, receptors, or antigen.
1. Channel Proteins And Carrier Proteins: Certain plasma membrane proteins are involved in passing molecules through the membrane. Some of those have a channel through which a substance can move across the membrane; others are carriers that combine with meaning and help it move across the membrane.
2. Enzymes: Some plasma membrane proteins have enzymatic functions, e.g., Adenylate cyclase, which converts ATP to cyclic AMP (cAMP).
3. Receptor molecules: Some proteins in the plasma membrane act as receptors that receive signals from other cells. Each type of receptor has a specific shape. The binding of a molecule on a receptor can bring about an intracellular response. For Example; Hormones circulate in the blood but bind to particular target cells with specific receptors.
4. Antigens: Some proteins are Antigens that enable the cells to recognize other cells; for example, the foreign antigens can be recognized and attacked by the immune system.
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