Plasma Membrane short note in pdf Download

 Plasma Membrane

The plasma membrane of a cell is a network of lipids and proteins that forms the boundary between a cell's contents and the outside of the cells. Plasma membrane is also termed as cell membrane.

The main function of the plasma membrane is to protect the cell from its surrounding environment. It is semi-permeable and regulates the material that enter and exit the cells.

Functions of the plasma membrane :-

• A physical barrier
• Selective Permeability
• Endocytosis and Exocytosis.
• Cell signaling
• acts as a receptor (hormone receptor)
• receives chemical messengers from other cell
• maintains intgrity of the cell - size and shape
• maintains ionic concentration of cell and osmotic pressure of the cytosol

Components of plasma membrane:-

It is composed of the following constituents:-

• Phospholipids:- The membrane is partially made up of the molecules called phospholipids, which spontaneouly arrange themselves into a double layer with hydrophilic("water loving") heads on the outside and hydrophobic ("water hating") tails on the inside. These interactions with water are what allow plasma membranes to from phospholipids forms the ultimate fubric of the membrane.
• Proteins:- Proteins are wedged between the lipids that make up the membrane.Proteins in the cell membrane play a role in many other functions, such as cell signaling, cell recognition, and enzyme activity.

Types of Membrane Proteins

1. Integral membrane proteins:- Integral proteins are permanently anchored and embedded within the lipid bilayer.
2. Peripheral membrane proteins:- They are only temporarily attached to the lipid bilayer or to other integral proteins. Peripheral proteins are less mobile within the lipid bilayer.

Composition of Plasma Membrane:-

1. Phospholipids
2. Proteins
3. Carbohydrates

Phospholipids:- Most carbohydrates in the membrane are part of glycoproteins, which are formed when a carbohydrate attaches to a protein. Glycoproteins play a role in the interactions between cells, including cell adhesion, the process by which cells attach to each other.

Proteins:- Proteins are wedged between the lipids that make up the membrane, and these transmembrane proteins allow molecules that couldn’t enter the cell otherwise to pass through by forming channels, pores or gates.

Carbohydrates:- Carbohydrates are also found in the plasma membrane; specifically, most carbohydrates in the membrane are part of glycoproteins, which are formed when a carbohydrate attaches to a protein.

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