Multiple Choice
In the context of the lipid bilayer, which structure primarily controls what goes in and out of the cell?
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8. Membrane Structure
The Lipid Bilayer
Multiple Choice
In the context of the lipid bilayer, where is cholesterol primarily located in animal cell membranes?
A
Intercalated between phospholipid molecules within the hydrophobic core of the bilayer, with its hydroxyl group near the polar head groups
B
Confined to the aqueous cytosol, where it forms soluble complexes with phospholipid head groups
C
Covalently attached to the carbohydrate chains of glycoproteins on the extracellular surface
D
Present only in the nucleus, where it stabilizes chromatin by binding directly to DNA
Verified step by step guidance1
Recall the structure of the lipid bilayer in animal cell membranes, which consists of two layers of phospholipids with hydrophilic (polar) head groups facing outward and hydrophobic (nonpolar) tails facing inward.
Understand that cholesterol is a lipid molecule with a small polar hydroxyl (-OH) group and a large hydrophobic steroid ring structure.
Recognize that cholesterol's amphipathic nature allows it to insert itself into the membrane, where its hydrophobic rings interact with the fatty acid tails of phospholipids, and its hydroxyl group aligns near the polar head groups.
Eliminate options that place cholesterol in aqueous environments or covalently attached to proteins or DNA, as cholesterol is not soluble in water and does not form covalent bonds with carbohydrates or DNA.
Conclude that cholesterol is primarily located intercalated between phospholipid molecules within the hydrophobic core of the bilayer, with its hydroxyl group near the polar head groups, helping to modulate membrane fluidity and stability.
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