4.Cholesterol and phospholipids are both amphipathic lipids that do not dissolve in water. Justify.

answer:

Hint: Amphipathic molecules are also known as amphiphilic molecules. Cholesterol, detergents, and phospholipids are an example of amphipathic molecules.

Complete Answer:
- The chemical compounds which have at least one hydrophilic portion and one hydrophobic portion are called amphipathic molecules. They contain properties of both types.
- Most membrane lipids are amphipathic. The typical example is phospholipids found in the cell membrane. The hydrophilic region is also called the water-loving head and face outside. On the contrary, the hydrophobic region also called water-repelling ends has two tails of fatty acids.
- Hydrophobic tails usually face towards the center of the membrane. This makes the cell membrane a lipid bilayer. Another example is soap, which has a hydrophilic head and a hydrophobic tail, allowing it to dissolve in both water and oil.

Cholesterol is referred to as an amphipathic molecule, that it contains its hydrophilic and hydrophobic parts. The hydroxyl group (-OH) in cholesterol is aligned with the phosphate head of the phospholipid on the cell membrane, which the rest of the cholesterol goes with the fatty acid of the membrane.

Phospholipids are amphipathic molecules. This means that they have a hydrophilic, polar phosphate head and two hydrophobic fatty acid tails. These components of the phospholipids cause them to orientate themselves, so the phosphate head can interact with water and the fatty acid tails can't, hence forming a bilayer.