Question

What is true of the fluid mosaic model?
A. Phospholipid monolayer is present over the protein layer
B. Phospholipid bilayer is present over the protein layer
C. Protein embedded in the phospholipid bilayer
D. The phospholipid layer is sandwiched between two protein layers

Answer 1

Hint: Cell membrane protects the cell from the outer environment and also permits the entry and exit of molecules inside and outside of the cell.

Complete answer: Fluid mosaic model is used to express the structure of cell membrane Fluid mosaic model of the cell membrane is composed of a phospholipid bilayer with proteins embedded in the phospholipid layer. It was given by Singer and Nicolson in 1972. The cell membrane is made up of phospholipids, proteins, carbohydrates, and cholesterol. The cell membrane has a quasi fluid-structure
Phospholipids are made up of glycerol, two fatty acids, and a phosphate group. Phospholipids have a polar hydrophilic head and a non-polar hydrophobic head. The polar portion faces to the outside and the non-polar portion faces another non-polar portion giving a bilayer appearance. Proteins are also part of the cell membrane. It is of two types extrinsic and intrinsic proteins. Extrinsic proteins are soluble and present on the outer surface of the membrane whereas intrinsic proteins are partially or completely embedded on the inner surface of the bilayer and lateral diffusion occurs through it. Molecules present in the cell membrane are constantly moving in two dimensions which give the membrane a fluid nature
Hence option C, i.e., Proteins embedded in phospholipid bilayer is true

Note: Cell membrane limits the cell from the outer environment and also guards the entry and exit of molecules across the cell membrane. The main molecules present in the cell membrane are phospholipid bilayer, extrinsic and intrinsic proteins, cholesterol. The fluidity of the membrane is dependent on the movement of molecules similar to icebergs floating in the ocean. Other factors that maintain fluidity are temperature, cholesterol, and saturated or unsaturated fatty acids.