Final answer:
The phospholipid bilayer consists of two layers of amphipathic phospholipids with hydrophobic tails and hydrophilic heads, creating a semi-permeable membrane critical for cell structure and function.
Step-by-step explanation:
The characteristics of the phospholipid bilayer are foundational to the structure and function of the plasma membrane in cells. A phospholipid molecule is composed of a hydrophilic (water-loving) head, which includes a phosphate group, and a hydrophobic (water-fearing) tail, made up of fatty acids. When phospholipids are in an aqueous environment, they arrange themselves into a bilayer, with the hydrophobic tails facing inward, away from the water, and the hydrophilic heads facing outward, touching the water. This configuration creates a barrier that separates the internal contents of the cell from the external environment.
The amphipathic nature of phospholipids allows for the formation of the lipid bilayer, which is semi-permeable and enables selective transport of substances. Additionally, the fluid mosaic model of the plasma membrane describes how various proteins and carbohydrates are embedded within or attached to the phospholipid bilayer, providing specialized functions such as material transport and cell recognition.
The fluidity of the membrane is influenced by factors such as temperature, the presence of cholesterol, and the proportion of saturated and unsaturated fatty acids in the phospholipid tails.