Question

Explain the structure of a biological membrane. Be sure to address how the phospholipids, proteins, glycolipids and glycoproteins are organized to create the biological membrane. (7 points)

Answer 1

Plasma membrane is the outermost covering present in both prokaryotic and Eukaryotic cell. It is selectively permeable in nature because it allows the movement of only selected molecules across the cell surface. Therefore it acts as a regulator for the movement of molecules.

The structure of plasma membrane is related to its function of regulating the movement of molecules.

Structure of plasma membrane

Plasma membrane is a lipid bilayer composed of phospholipids and proteins.

The phospholipids are made up of a hydrophilic phosphate head and a hydrophobic fatty acid tail. Because of the presence of both hydrophilic and hydrophobic characters, plasma membrane is said to be amphipathic in nature.

There are two leaflets in the plasma membrane, outer leaflet and the inner leaflets. That is why it is called as a bilayer.

Proteins are also present in the plasma membrane. There are two types of proteins, extrinsic and intrinsic. Extrinsic proteins are present on the Periphery of the plasma membrane. They are mainly enzymatic in nature. There also called as peripheral proteins. Intrinsic proteins are embedded inside the membrane and are also called as transmembrane proteins. They are mainly the membrane Transporters which allow the passage of molecules.

Cholesterol molecules are also present in the plasma membrane. They are mainly involved with reordering of phospholipid to regulate the passage of molecules.

Plasma membrane is asymmetric in nature due to the distribution of proteins, cholesterol and lipids. The type of lipids present in the to leaflet of the plasma membrane are also different.

Lipids are present in patches in the plasma membrane. These patches are called as lipid rafts.

Fatty acids present in phospholipids are of two types, unsaturated and saturated. Saturated fatty acids are those which do not have Double bonds and therefore pack tightly with each other. And saturated fatty acids are those which have Double bonds and therefore have a bended appearance and do not pack tightly with each other.

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