Multiple Choice
Of the following movements a lipid can do in a membrane, which is the most rare?
8. Membrane Structure
The Lipid Bilayer
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Which of the following best describes the structure of the lipid bilayer as shown in the image?
A
A double helix of phospholipids similar to DNA
B
A single layer of phospholipids with hydrophilic heads facing inward
C
Two layers of proteins with hydrophobic regions facing outward
D
Two layers of phospholipids with hydrophobic tails facing inward and hydrophilic heads facing outward
Verified step by step guidance1
Understand the structure of the lipid bilayer: The lipid bilayer is a fundamental component of cell membranes, composed of two layers of phospholipids. Each phospholipid molecule has a hydrophilic (water-attracting) head and two hydrophobic (water-repelling) tails.
Visualize the arrangement of phospholipids: In the bilayer, the hydrophilic heads face outward toward the aqueous environment (both inside and outside the cell), while the hydrophobic tails face inward, away from water, creating a nonpolar interior.
Eliminate incorrect options: A double helix of phospholipids is incorrect because this structure is specific to DNA, not lipids. A single layer of phospholipids with hydrophilic heads facing inward is also incorrect because the bilayer has two layers, not one. Two layers of proteins with hydrophobic regions facing outward is incorrect because the bilayer is primarily composed of phospholipids, not proteins.
Confirm the correct description: The correct description is 'Two layers of phospholipids with hydrophobic tails facing inward and hydrophilic heads facing outward,' as this matches the known structure of the lipid bilayer.
Relate to biological function: This arrangement is critical for the bilayer's role as a selective barrier, allowing the cell to maintain its internal environment while controlling the movement of substances in and out of the cell.
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The Lipid Bilayer practice set
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