Question

Phospholipids are important cell membrane constituents because they
(a) Contain glycerol
(b) Combine covalently with proteins
(c) Contain both polar and nonpolar portion
(d) Can form bilayers in water

Answer 1

Hint: Membrane phospholipids are amphiphilic i.e. they possess one end that is soluble in water and another end that is insoluble in water (nonpolar, soluble in fat). By forming a double layer the phospholipid membrane keeps the watery interior of the cell separate from the watery exterior.

Complete answer:
Phospholipids are important cell membrane constituents because they can form bilayers in water. Studies have shown that the cell membrane is primarily composed of lipids and proteins. The major lipids present are phospholipids which are arranged in a bilayer. These are arranged within the membrane with the polar head towards the outer sides and hydrophobic tail towards the inner part. This ensures that the nonpolar tail of unsaturated hydrocarbons is kept away from direct contact with the aqueous environment. Along with phospholipids, the cell membrane also contains cholesterol, glycolipids, proteins, and carbohydrates. Phospholipids are a type of lipids that have a group of phosphate attached to their chemical structure. An example of phospholipids is lecithin. The arrangement of lipids and a number of proteins acting as receptors and channel pores in the membrane controls the entry and exit of molecules and ions as part of the cell's metabolism.
So, the correct answer is, ‘Can form bilayers in the water.’

Note: -Phospholipids within the cell membrane are formed by two hydrophobic fatty acid tails and a hydrophilic head. There is a phosphate group attached to the hydrophilic head.
-The two hydrophobic and hydrophilic portions are united by a molecule of glycerol.
-The membrane phospholipid possesses the ability to form bilayers because of being cylindrical and exhibiting an amphiphilic nature.