Multiple Choice
In the context of the lipid bilayer, what is the hydrophilic head of a phospholipid primarily made of?
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8. Membrane Structure
The Lipid Bilayer
Multiple Choice
In the context of the lipid bilayer, what is the primary role of cholesterol in the cell membrane?
A
It forms the main hydrophilic barrier that prevents water from crossing the membrane.
B
It serves as the primary ATP-dependent pump responsible for establishing ion gradients across the membrane.
C
It buffers membrane fluidity by restraining phospholipid movement at high temperatures and preventing tight packing at low temperatures.
D
It covalently cross-links membrane proteins to rigidly lock the membrane in place.
Verified step by step guidance1
Understand the structure of the lipid bilayer: it is primarily composed of phospholipids with hydrophilic heads facing outward and hydrophobic tails inward, creating a semi-permeable membrane.
Recognize that cholesterol is a lipid molecule interspersed within the phospholipid bilayer, influencing membrane properties rather than forming a barrier or acting as a pump.
Recall that cholesterol's role is to modulate membrane fluidity by interacting with phospholipid tails, preventing them from moving too freely at high temperatures and stopping them from packing too tightly at low temperatures.
Eliminate incorrect options by understanding that cholesterol does not form the hydrophilic barrier (this is the role of phospholipid heads), does not function as an ATP-dependent pump (this is the role of membrane proteins like ion pumps), and does not covalently cross-link proteins (membrane proteins are generally not covalently cross-linked by cholesterol).
Conclude that the primary role of cholesterol in the cell membrane is to buffer membrane fluidity, maintaining membrane stability and functionality across temperature changes.
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