Question

According to fluid mosaic model,plasma membrane is composed of
A. Phospholipids and oligosaccharides
B. Phospholipids and hemicellulose
C. Phospholipids and integral proteins
D. Phospholipids extrinsic proteins and intrinsic proteins

Answer 1

Hint: The border of the cell is defined by the plasma membrane, also known as the cell surface membrane or plasmalemma. They are a distinctive type of membranes that are structures of lipids that distinguish the cell from its environment.

Complete Answer:
- The fluid mosaic model identifies the plasma membrane structure as a mosaic of components, including phospholipids, cholesterol, proteins and carbohydrates, giving a fluid character to the membrane.
- Membranes are impermeable to most polar or charged solutes, but they are permeable to non-polar compounds; they are thick from 5 to 8 nm (50 to 80 Å) and appear trilaminar when viewed with an electron microscope in cross-section.
- The combined evidence from electron microscopy and chemical composition research, as well as physical studies of the permeability and movement inside membranes of individual protein and lipid molecules, contributed to the creation of the fluid mosaic model for biological membrane structure.
- The basic architecture of all cell membranes with membrane proteins is given by a bilayer of phospholipids about 3 nm thick, giving each cell membrane its own specific set of functions.
- Thus a lipid bilayer containing embedded and peripheral proteins consists of the plasma membrane. Lipids, however, are the main component of membranes. Inside the plane of the membrane, individual phospholipids can travel laterally and spin, giving the membrane a fluid-like consistency similar to that of olive oil.
- Membrane lipids with a polar hydrophilic "head group" and a polar hydrophobic tail" are strongly amphipathic molecules. Two hydrophobic fatty acid tails are connected to the polar head group; the head group faces the aqueous world, the fatty acid tails to the bilayer interior.
- In membranes, the hydrophobic effect and weak Van der Waals forces mainly hold them together and are thus mobile relative to each other. This gives a more or less fluid quality to membranes.
- Non-covalent interactions between phospholipids and between proteins and phospholipids also give the membrane strength and resilience.

Two types of transmembrane proteins are:
- Outside the membrane, which is bound to the lipid layer by weak molecular forces, extrinsic membrane proteins are present.
- Proteins of the intrinsic membrane-are completely incorporated in the membrane.
- The plasma membrane's proteins also make extensive contact with the cytoskeleton.
- Within the membrane, lipids and proteins are mobile. If they are not fixed by special mechanisms in place, they float within the lipid layer like in a two-dimensional liquid; thus, biological membranes are often defined as a fluid mosaic.

The correct Answer is option (D)Phospholipids extrinsic proteins and intrinsic proteins.

Note: In the year 1972, SJ Singer and GL Nicolson suggested the fluid mosaic model of the biomembrane or cell membrane.These carbohydrates, the carbohydrate bases of both glycoproteins and glycolipids, are collectively referred to as glycocalyx (meaning "sugar coating") on the outer surface of the cell. Glycocalyx is extremely hydrophilic and draws large quantities of water to the cell's surface. This assists in the cell's contact with its watery environment and the ability of the cell to receive dissolved substances in the water.