Which of the following statements best describes the structure of a membrane based on the fluid mosaic model? A/ The membrane is composed of a single layer of fluid phospholipids between two layers of hydrophilic proteins. B/ The membrane is composed of a fluid bilayer of phospholipids with embedded amphipathic proteins. C/ The membrane is composed of a fluid bilayer of phospholipids between two layers of hydrophilic proteins. D/ The membrane is composed of a mosaic of fluid polysaccharides and amphipathic proteins.
The correct answer and explanation is:
The correct answer is B/ The membrane is composed of a fluid bilayer of phospholipids with embedded amphipathic proteins.
Explanation:
The fluid mosaic model of biological membranes describes the structure of the plasma membrane in a way that highlights its dynamic and flexible nature. The model posits that the membrane is primarily composed of a phospholipid bilayer, which is fluid and allows for lateral movement of the molecules within it. Phospholipids, the primary building blocks of the membrane, have a hydrophilic (water-loving) head and two hydrophobic (water-fearing) tails. The hydrophilic heads face outward towards the aqueous environment, while the hydrophobic tails face inward, shielded from water. This arrangement creates a stable barrier between the interior and exterior of the cell.
Embedded within this fluid bilayer are amphipathic proteins, meaning that these proteins have both hydrophilic and hydrophobic regions. These proteins can be integral (spanning across the membrane) or peripheral (associated with one side of the membrane). The amphipathic nature of these proteins allows them to interact with both the hydrophobic interior and the hydrophilic exterior of the membrane, facilitating various functions like transport, signaling, and structural support.
The “mosaic” aspect of the model refers to the diverse proteins scattered throughout the lipid bilayer, contributing to the membrane’s functional complexity. These proteins are not fixed in place but can move laterally within the membrane, which adds to its fluid nature.
Overall, the fluid mosaic model emphasizes the dynamic and flexible nature of the membrane, where both lipids and proteins are free to move, creating a highly adaptable and functional barrier.