Multiple Choice
Why is it more appropriate to describe biological membranes as semifluid rather than fluid?
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6. The Membrane
Biological Membranes
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Which of the following will pass through a cell membrane most easily?
A
Large polar molecules
B
Ions
C
Proteins
D
Small nonpolar molecules
Verified step by step guidance1
Understand the structure of the cell membrane: The cell membrane is primarily composed of a phospholipid bilayer, which has hydrophilic (water-attracting) heads and hydrophobic (water-repelling) tails.
Recognize the properties of molecules that affect their ability to pass through the cell membrane: Small nonpolar molecules can easily pass through the hydrophobic core of the phospholipid bilayer, while large polar molecules, ions, and proteins typically cannot.
Consider the size of the molecules: Small molecules can pass through more easily than large molecules because they can fit between the phospholipids.
Consider the polarity of the molecules: Nonpolar molecules can pass through the hydrophobic core of the membrane more easily than polar molecules, which are repelled by the hydrophobic tails.
Apply this understanding to the options given: Small nonpolar molecules will pass through the cell membrane most easily compared to large polar molecules, ions, and proteins.
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