In a diagram of the lipid bilayer where the polar heads are represented by circles, what do the lines extending from the circles most likely represent?

• A. Cholesterol molecules
• B. Carbohydrate side chains
• C. Integral membrane proteins
• D. The hydrophobic fatty acid tails

Answer: (D)

Verified step by step guidance

1. Understand the structure of the lipid bilayer: The lipid bilayer is composed of phospholipids, which have a polar (hydrophilic) head group and two nonpolar (hydrophobic) fatty acid tails.
2. Interpret the diagram: In the diagram, the circles represent the polar head groups of the phospholipids. These are hydrophilic and face the aqueous environment on either side of the bilayer.
3. Analyze the lines extending from the circles: The lines represent the nonpolar fatty acid tails of the phospholipids. These tails are hydrophobic and face inward, away from the aqueous environment, forming the core of the bilayer.
4. Eliminate incorrect options: Cholesterol molecules are interspersed within the bilayer but are not represented as lines extending from the circles. Carbohydrate side chains are attached to proteins or lipids on the extracellular side of the membrane, and integral membrane proteins span or are embedded in the bilayer but are not represented as lines extending from the circles.
5. Conclude the correct answer: The lines extending from the circles most likely represent the hydrophobic fatty acid tails of the phospholipids, which are a key component of the lipid bilayer.