Multiple Choice
In the context of the lipid bilayer, what is the primary role of cholesterol in the plasma membrane?
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8. Membrane Structure
The Lipid Bilayer
Multiple Choice
In the context of the lipid bilayer, the cell (plasma) membrane is best described as being what kind of permeable?
A
Freely permeable to all ions and polar molecules because of the hydrophobic core
B
Impermeable to water because water is polar
C
Equally permeable to all molecules as long as they are small
D
Selectively permeable (semipermeable), allowing some substances to cross more easily than others
Verified step by step guidance1
Understand the structure of the lipid bilayer: it consists of hydrophilic (water-attracting) heads facing outward and hydrophobic (water-repelling) tails facing inward, creating a hydrophobic core.
Recognize that the hydrophobic core acts as a barrier to most polar molecules and ions, preventing them from freely crossing the membrane.
Know that small nonpolar molecules and some small uncharged polar molecules can pass through the membrane more easily due to their compatibility with the hydrophobic interior.
Realize that water, although polar, can cross the membrane but often requires specialized channels called aquaporins to do so efficiently.
Conclude that the membrane is selectively permeable (semipermeable), meaning it allows certain substances to cross more readily than others based on size, polarity, and charge.
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