How do phospholipids contribute to the structure of cell membranes?

• A. They form a bilayer with hydrophobic tails facing inward and hydrophilic heads facing outward.
• B. They act as enzymes to facilitate biochemical reactions within the membrane.
• C. They provide energy for active transport processes across the membrane.
• D. They create a rigid structure that prevents any movement of molecules across the membrane.

Answer: (A)

Verified step by step guidance

1. Understand the basic structure of phospholipids: Phospholipids are composed of a hydrophilic (water-attracting) 'head' and two hydrophobic (water-repelling) 'tails'.
2. Recognize the arrangement of phospholipids in a cell membrane: In an aqueous environment, phospholipids arrange themselves into a bilayer, with the hydrophobic tails facing inward, shielded from water, and the hydrophilic heads facing outward, interacting with the aqueous environment.
3. Identify the role of the phospholipid bilayer: This arrangement forms the fundamental structure of cell membranes, creating a semi-permeable barrier that separates the interior of the cell from the external environment.
4. Differentiate the functions of phospholipids from other membrane components: While phospholipids form the structural basis of the membrane, proteins embedded within the membrane perform various functions such as transport, signaling, and acting as enzymes.
5. Clarify misconceptions: Phospholipids do not act as enzymes, provide energy, or create a rigid structure. Instead, they contribute to the fluidity and flexibility of the membrane, allowing for the movement of molecules and the dynamic nature of the cell membrane.