Multiple Choice
In the context of the lipid bilayer, which set correctly lists the three main components of a phospholipid molecule?
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8. Membrane Structure
The Lipid Bilayer
Multiple Choice
In a typical cell membrane lipid bilayer, how are phospholipids arranged?
A
As a bilayer with hydrophobic tails facing the aqueous cytosol and extracellular fluid and hydrophilic heads oriented inward
B
As a rigid crystalline sheet with phospholipids covalently cross-linked to each other
C
As a single layer with hydrophobic tails facing the aqueous environments on both sides
D
As a bilayer with hydrophilic heads facing the aqueous cytosol and extracellular fluid and hydrophobic tails oriented inward toward each other
Verified step by step guidance1
Recall the basic structure of a phospholipid molecule: it has a hydrophilic (water-attracting) head and two hydrophobic (water-repelling) fatty acid tails.
Understand that in an aqueous environment, phospholipids spontaneously arrange themselves to minimize the exposure of their hydrophobic tails to water, while maximizing the interaction of their hydrophilic heads with water.
Recognize that this leads to the formation of a bilayer, where two layers of phospholipids align tail-to-tail, creating a hydrophobic interior and hydrophilic surfaces on both sides.
Note that the hydrophilic heads face outward toward the aqueous cytosol inside the cell and the extracellular fluid outside the cell, while the hydrophobic tails face inward, away from water.
Conclude that this arrangement forms the fundamental structure of the cell membrane, providing a semi-permeable barrier essential for cell function.
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