Question

Why do phospholipids tend to spontaneously orient themselves into something resembling a membrane such as the lipid-bilayer sphere, single-layer lipid sphere, and lipid-bilayer sheet?

a) Due to the hydrophilic nature of the phosphate head.
b) Because of the hydrophobic nature of the fatty acid tails.
c) It is dictated by the presence of cholesterol.
d) Phospholipids have a natural attraction to proteins.

Answer 1

Phospholipids self-assemble into lipid bilayers due to their amphipathic nature, with hydrophilic heads facing water and hydrophobic tails avoiding water, resulting in a stable, energy-minimized structure essential for biological membranes.

Step-by-step explanation:

Phospholipids spontaneously orient themselves into structures such as a lipid-bilayer sphere, single-layer lipid sphere, and lipid-bilayer sheet because of their amphipathic nature. This means that they have both hydrophilic (water-attracting) heads and hydrophobic (water-repelling) tails. When in an aqueous environment, the hydrophilic phosphate heads orient towards the water, while the hydrophobic fatty acid tails avoid water and face each other. This arrangement minimizes the energy state of the system by reducing the exposure of hydrophobic tails to water, leading to the spontaneous formation of micelles or bilayers, critical in biological membranes.

At higher concentrations of phospholipids, they form a bilayer, as seen in cell membranes. This bilayer acts as a barrier, organizing into a structure that separates water and other materials on one side from those on the other side. The arrangement of phospholipids in aqueous solutions ensures that cellular contents are enclosed and that cells maintain a distinct internal environment.