Multiple Choice
Which class of macromolecule primarily makes up the structural framework of the cell membrane (lipid bilayer)?
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8. Membrane Structure
The Lipid Bilayer
Multiple Choice
In the context of the lipid bilayer, how are phospholipids arranged in the cell membrane?
A
They form a bilayer with hydrophobic tails facing outward toward the aqueous environments and hydrophilic heads facing inward away from water.
B
They form micelles in which hydrophilic heads cluster at the center and hydrophobic tails face outward toward water.
C
They form a bilayer with hydrophilic phosphate heads facing the aqueous cytosol and extracellular fluid and hydrophobic fatty acid tails facing inward toward each other.
D
They form a single layer with hydrophobic tails facing the cytosol and hydrophilic heads facing the extracellular fluid.
Verified step by step guidance1
Understand the basic structure of a phospholipid molecule: it has a hydrophilic (water-attracting) phosphate head and two hydrophobic (water-repelling) fatty acid tails.
Recall that in an aqueous environment, phospholipids spontaneously arrange themselves to minimize the exposure of hydrophobic tails to water while maximizing the interaction of hydrophilic heads with water.
Recognize that this arrangement 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.
Identify that the hydrophilic phosphate heads face outward toward the aqueous environments: the cytosol inside the cell and the extracellular fluid outside the cell.
Conclude that this bilayer structure forms the fundamental architecture of the cell membrane, providing a selective barrier that separates the cell interior from its environment.
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