Question

Cholesterol mixes with phospholipids in a biomembrane because cholesterol molecules are:

1) amphipathic
2) steroid derivatives
3) entirely hydrophobic
4) phospholipid derivatives

Answer 1

Cholesterol mixes with phospholipids in a biomembrane because they are both amphipathic, containing both hydrophilic and hydrophobic components, which enables them to interact together within the lipid bilayer of the membrane.

Step-by-step explanation:

Cholesterol molecules mix with phospholipids in a biomembrane because cholesterol molecules are amphipathic. Like phospholipids, cholesterol has both hydrophilic (water-loving) and hydrophobic (water-fearing) parts. The hydrophilic part is the -OH group (polar head) and the hydrophobic part is the cholestane structure (hydrophobic tail). The amphipathic nature of cholesterol allows it to interact with the hydrophilic heads and the hydrophobic tails of the phospholipids in the membrane, maintaining membrane integrity and fluidity.

Phospholipids are also amphipathic molecules, crucial for forming the lipid bilayer of cell membranes. The phosphate-containing group of a phospholipid is hydrophilic, while the fatty acid chains are hydrophobic. When arranged in a bilayer, the hydrophobic tails face inward, shielded from water, with the hydrophilic heads facing outward, interacting with the aqueous environment. This arrangement encapsulates the hydrophobic tails, creating a stable barrier for the cell.