The cytoplasm of a cell is encased in a thin semi-permeable membrane known as the cell membrane (plasma membrane). Its purpose is to protect the cell’s interior integrity by allowing certain substances into the cell while preventing others from entering. In some organisms, it also serves as a base of attachment for the cytoskeleton.
Structure of the Cell Membrane
The majority of the cell membrane comprises proteins and lipids, and Lipids can make up anywhere from 20% to 80% of a membrane. Depending on its location and function in the body, proteins account for the rest. Proteins help move molecules across the membrane by monitoring and maintaining the cell’s chemical climate.
Lipids in Cell Membranes
Phospholipids form a lipid bilayer with their hydrophilic (water-loving) head areas facing the aqueous cytosol and extracellular fluid and their hydrophobic (water-repelling) tail areas facing away from the cytosol and extracellular fluid. Only specific molecules can diffuse across the membrane because the lipid bilayer is semi-permeable.
Cholesterol is a lipid that is found in animal cell membranes. Cholesterol molecules are dispersed between membrane phospholipids selectively. By preventing phospholipids from being too closely packed together, it helps to keep cell membranes from becoming stiff. Cholesterol is not found in plant cell membranes.
Membrane Proteins in Cells
There are two types of associated proteins in the cell membrane. Peripheral membrane proteins are found outside the membrane and are connected to it through interactions with other proteins. The majority of integral membrane proteins pass through the membrane after being inserted into it. On both sides of the membrane, portions of these transmembrane proteins are exposed.
Structural proteins aid in the support and shape of the cell.
Cell membrane receptor proteins use hormones, neurotransmitters, and other signaling molecules to help cells communicate with their surroundings.
Transport proteins like globular proteins help chemicals pass cell membranes more easily.
A carbohydrate chain is attached to glycoproteins. They are embedded in the cell membrane and assist in cell-to-cell communication and molecule transport across it.
Bio chemistry 