Multiple Choice
Which set correctly lists the three main components of a typical glycerophospholipid in the lipid bilayer?
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8. Membrane Structure
The Lipid Bilayer
Multiple Choice
The cell membrane is selectively permeable, which means:
A
It allows all substances to pass freely across the membrane in either direction.
B
It permits only water to cross the membrane and blocks all solutes.
C
It allows some substances to cross the membrane more easily than others while restricting the passage of certain molecules and ions.
D
It prevents all substances from entering or leaving the cell under all conditions.
Verified step by step guidance1
Understand the term 'selectively permeable' in the context of the cell membrane. It means the membrane controls what substances can pass through it, rather than allowing everything or nothing to pass.
Recall that the cell membrane is composed mainly of a phospholipid bilayer with embedded proteins, which creates a barrier that is permeable to some molecules but not others.
Recognize that small, nonpolar molecules (like oxygen and carbon dioxide) can pass through the membrane more easily, while larger or charged molecules (like ions and glucose) require specific transport proteins.
Note that water can cross the membrane through specialized channels called aquaporins, but the membrane does not allow all solutes to pass freely.
Conclude that the correct understanding is that the membrane allows some substances to cross more easily than others, restricting certain molecules and ions, which matches the definition of selective permeability.
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