Explain of plasma membrane cell _07-03_Full HD
- 5 years ago
Plasma membrane
The cell is bound by the living outer boundary called plasma membrane. The major chemical constituents of plasma membrane are the proteins, lipids, and carbohydrates. According to the unit membrane model of Robertson, the plasma membrane consists of two layers of molecules, each about 20 Å thick, with a central layer of about 35 Å thick, forming a total thickness of 75 Å. According to the Fluid Mosaic model of Singer and Nicholson, there is a double layer of lipid molecules (phospholipids) with globular protein molecules and sterols which are arranged differently in different parts of the plasma membrane. The plasma membrane is ‘selectively permeable’ and regulates the flow of materials in and out of the cell. The vital functions of plasma membrane are protection and support, passive and active transport of molecules, phagocytosis (or cell eating), and pinocytosis (cell drinking).
Cell surface proteins
Cell membranes essentially consist of lipoproteins, which are special non-bonded combination of lipids with proteins. Cell membrane proteins are grouped as structural proteins and carrier proteins. Structural proteins form the ‘backbone’ of the cell membrane with little catalytic activity and lipophilic nature. Structural proteins fall into two main categories – intrinsic or integral proteins and extrinsic or peripheral proteins. Carrier proteins or permeases transport substances across the membrane against the concentration gradient.
The cell is bound by the living outer boundary called plasma membrane. The major chemical constituents of plasma membrane are the proteins, lipids, and carbohydrates. According to the unit membrane model of Robertson, the plasma membrane consists of two layers of molecules, each about 20 Å thick, with a central layer of about 35 Å thick, forming a total thickness of 75 Å. According to the Fluid Mosaic model of Singer and Nicholson, there is a double layer of lipid molecules (phospholipids) with globular protein molecules and sterols which are arranged differently in different parts of the plasma membrane. The plasma membrane is ‘selectively permeable’ and regulates the flow of materials in and out of the cell. The vital functions of plasma membrane are protection and support, passive and active transport of molecules, phagocytosis (or cell eating), and pinocytosis (cell drinking).
Cell surface proteins
Cell membranes essentially consist of lipoproteins, which are special non-bonded combination of lipids with proteins. Cell membrane proteins are grouped as structural proteins and carrier proteins. Structural proteins form the ‘backbone’ of the cell membrane with little catalytic activity and lipophilic nature. Structural proteins fall into two main categories – intrinsic or integral proteins and extrinsic or peripheral proteins. Carrier proteins or permeases transport substances across the membrane against the concentration gradient.