Multiple Choice
Which phrase best describes the property of selective permeability in biological membranes?
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6. The Membrane
Biological Membranes
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When an animal's body has extended exposure to ______, cell membranes become less fluid.
A
high temperatures
B
high concentrations of unsaturated fatty acids
C
low temperatures
D
increased cholesterol at high temperatures
Verified step by step guidance1
Understand the concept of membrane fluidity: Cell membranes are composed of a lipid bilayer, primarily made of phospholipids, cholesterol, and proteins. The fluidity of the membrane is crucial for its function, including transport and signaling.
Analyze the effect of temperature: At low temperatures, the movement of phospholipids slows down, causing the membrane to become less fluid and more rigid. Conversely, at high temperatures, phospholipids move more rapidly, increasing fluidity.
Consider the role of unsaturated fatty acids: Unsaturated fatty acids have kinks in their structure due to double bonds, which prevent tight packing of lipids and increase fluidity. High concentrations of unsaturated fatty acids would make the membrane more fluid, not less.
Evaluate the impact of cholesterol: Cholesterol acts as a buffer for membrane fluidity. At high temperatures, it stabilizes the membrane by reducing excessive fluidity, while at low temperatures, it prevents the membrane from becoming too rigid.
Conclude the correct answer: Extended exposure to low temperatures causes cell membranes to become less fluid because the movement of lipids slows down, and the membrane becomes more rigid.
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