Final answer:
The fluid mosaic model describes cellular membranes as a dynamic arrangement of phospholipids, cholesterol, proteins, and carbohydrates, able to move within the bilayer, which contributes to the fluid nature of membranes.
Step-by-step explanation:
The composition and structure of membranes can be described using the fluid mosaic model. This model illustrates that cellular membranes are composed of a phospholipid bilayer where the phospholipids and proteins have the ability to move laterally. These components, which include phospholipids, cholesterol, proteins, and carbohydrates, are arranged in a mosaic-like pattern, giving the membrane its fluid characteristic.
The bilayer structure consists of hydrophobic fatty acid tails facing inward, shielded from water, while the hydrophilic heads face outward. Cholesterol molecules interspersed within the membrane contribute to its fluidity. Proteins embedded in the membrane serve various functions, such as transportation and cell communication, and may be attached to carbohydrates, acting as identification markers for the cell. The membrane's fluid nature is regulated by factors like temperature, the presence of double bonds in the fatty acid tails, and the cholesterol content. Overall, plasma membranes are dynamic, maintaining a thickness between 5 to 10 nm.