Multiple Choice
How is a cell wall different from a cell membrane?
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6. The Membrane
Biological Membranes
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Which characteristic of the plasma membrane contributes to its selective permeability?
A
The phospholipid bilayer structure
B
The presence of cholesterol molecules
C
The rigid structure of the membrane
D
The uniform distribution of proteins
Verified step by step guidance1
Understand the concept of selective permeability: Selective permeability refers to the ability of the plasma membrane to allow certain molecules to pass through while blocking others. This is crucial for maintaining homeostasis within the cell.
Examine the structure of the plasma membrane: The plasma membrane is primarily composed of a phospholipid bilayer, which consists of two layers of phospholipids with hydrophilic (water-attracting) heads and hydrophobic (water-repelling) tails.
Analyze the role of the phospholipid bilayer: The arrangement of phospholipids in the bilayer creates a semi-permeable barrier. The hydrophobic core prevents the passage of polar or charged molecules, while allowing nonpolar molecules to pass through more easily.
Consider the presence of cholesterol molecules: Cholesterol is interspersed within the phospholipid bilayer, contributing to membrane fluidity and stability. It helps maintain the membrane's integrity and affects its permeability.
Evaluate the distribution of proteins: Proteins are embedded within the phospholipid bilayer and can act as channels or carriers, facilitating the selective transport of specific molecules across the membrane. Their distribution is not uniform, allowing for specialized functions.
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