Multiple Choice
In the context of the lipid bilayer, what are most cell membranes primarily made of?
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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 the cell (plasma) membrane?
A
It stores the cell’s genetic information and controls gene expression.
B
It is the main site of ATP production through oxidative phosphorylation in all cells.
C
It acts as a selectively permeable barrier that regulates movement of substances into and out of the cell.
D
It provides the enzymatic machinery for protein synthesis by translating mRNA into polypeptides.
Verified step by step guidance1
Step 1: Understand the structure of the cell (plasma) membrane, which is primarily composed of a lipid bilayer with embedded proteins. This structure is crucial for its function.
Step 2: Recognize that the plasma membrane's lipid bilayer creates a hydrophobic barrier that prevents free passage of most water-soluble substances, thus controlling what enters and exits the cell.
Step 3: Identify that the membrane is selectively permeable, meaning it allows certain molecules (like oxygen, nutrients, and waste products) to pass through while blocking others, maintaining the internal environment of the cell.
Step 4: Differentiate the plasma membrane's function from other cellular components: it does not store genetic information (that's the nucleus), it is not the main site of ATP production (that's the mitochondria), and it does not synthesize proteins (that's the ribosomes).
Step 5: Conclude that the primary function of the plasma membrane is to act as a selectively permeable barrier that regulates the movement of substances into and out of the cell, ensuring cellular homeostasis.
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