Question

Select the correct statement regarding cell membrane-
a. $Na^{+}$ and $K^{+}$ ions move across the cell membrane by passive transport.
b. Proteins make up 60 to 70 you take care of the cell membrane
c. Lipids are arranged in a bilayer with a polar head towards the inner part.
d. Fluid mosaic model of the cell membrane was proposed by singer and Nicolson

Answer 1

Hint: The cell membrane (also referred to as the plasma membrane (PM) may be a biological membrane that separates the inside of all cells from the surface environment (the extracellular space) which protects the cell from its environment. It protects a cell. The cell membrane is formed from glycerophospholipids, molecules composed of glycerol, a phosphate group, and two fatty acid chains.

Complete answer:
$Na^{+} - K^{+}$ ATPase, which carries sodium and potassium ions, and H+-$K^{+}$ ATPase, which carries hydrogen and potassium ions are regulated by active transport. Both of those are antiporter carrier proteins.

The cell membranes are primarily composed of lipids & proteins, and even have carbohydrates (1-10%)- present as glycolipids and glycoproteins.

All the lipids are amphipathic, with their hydrophilic (polar) and hydrophobic (nonpolar) portions located at separate parts of every molecule. In the lipid bilayer, lipids are arranged in a way such that the polar head towards the outer side and therefore the hydrophobic/ nonpolar tails towards the inner side.

In 1972, Singer and Nicolson proposed the Fluid mosaic model for the internal structure of the plasma membrane.

Hence, the correct answer is option (D).

Additional information:
It is the most accepted model of the structure of the biomembrane.
According to the fluid mosaic model, a membrane consists of a continuous bilayer of phospholipid molecules during which globular proteins are embedded. Cell membranes are quasi-fluid with a viscous lipid bilayer having proteins distributed at places both on the surface and inside.

According to this model, a membrane consists of a continuous bilayer of phospholipids with their polar hydrophilic ends on the outer surfaces and two non-polar hydrophobic tails of every phospholipid molecule point inwards.

Note: The plasma membrane contains about 50-60% of proteins and 50% lipids. Lipids form a bilayer with hydrophilic heads pointing outwards. The cell membrane allows transport of some molecules by passive transport e.g., water, neutral solutes while some are transported actively e.g., $Na^{+}/K^{+}$ pump. The globular alpha proteins don't form a continuous layer but are embedded randomly within the lipid bilayer or superficially attached.