Multiple Choice
In a cell membrane lipid bilayer, the phospholipid heads are primarily _____.
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8. Membrane Structure
The Lipid Bilayer
Multiple Choice
In the context of the lipid bilayer, what is the primary function of cholesterol in the cell membrane?
A
It forms the main aqueous channels that allow ions to cross the membrane by facilitated diffusion.
B
It covalently links phospholipid tails together to create a permanently rigid membrane structure.
C
It serves as the primary energy-storage molecule within the membrane for ATP production.
D
It buffers membrane fluidity by reducing permeability and preventing the membrane from becoming too rigid at low temperatures or too fluid at high temperatures.
Verified step by step guidance1
Understand the structure of the lipid bilayer, which is primarily composed of phospholipids arranged 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, interacting with the fatty acid tails of phospholipids.
Recall that cholesterol's role is not to form channels or covalent bonds but to modulate the physical properties of the membrane.
Analyze how cholesterol affects membrane fluidity: at low temperatures, it prevents the membrane from becoming too rigid by disrupting tight packing of phospholipids; at high temperatures, it stabilizes the membrane by restraining phospholipid movement, thus preventing excessive fluidity.
Conclude that cholesterol acts as a buffer for membrane fluidity and permeability, maintaining membrane integrity and proper function across temperature variations.
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