Which statement best describes the fluid mosaic model of biological membranes?

• A. Membranes are static structures with proteins fixed in place within the lipid bilayer.
• B. Membranes are rigid structures composed solely of tightly packed phospholipids.
• C. Membranes are made of a single layer of phospholipids with proteins attached only to the outer surface.
• D. Membranes consist of a phospholipid bilayer with proteins embedded throughout, allowing lateral movement of components.

Answer: (D)

Verified step by step guidance

1. Understand the concept of the fluid mosaic model: Biological membranes are dynamic structures composed of a phospholipid bilayer with embedded proteins and other molecules. The term 'fluid' refers to the lateral movement of components within the membrane, while 'mosaic' describes the diverse composition of lipids, proteins, and carbohydrates.
2. Analyze the structure of the phospholipid bilayer: Phospholipids have hydrophilic (water-attracting) heads and hydrophobic (water-repelling) tails. They arrange themselves into a bilayer, with the hydrophobic tails facing inward and the hydrophilic heads facing outward, creating a semi-permeable barrier.
3. Examine the role of embedded proteins: Proteins within the membrane can be integral (spanning the bilayer) or peripheral (attached to the surface). These proteins serve various functions, such as transport, signaling, and structural support, and they can move laterally within the bilayer.
4. Consider the dynamic nature of the membrane: The fluid mosaic model emphasizes that the membrane is not rigid. Lipids and proteins can move laterally, allowing the membrane to adapt to changes in the environment and maintain its functionality.
5. Compare the given statements to the fluid mosaic model: The correct answer aligns with the model's description, stating that membranes consist of a phospholipid bilayer with proteins embedded throughout, allowing lateral movement of components. The other statements incorrectly describe membranes as static, rigid, or composed of a single layer.