Multiple Choice
Which of the following molecules are found on the surface of human blood cells and are responsible for determining blood type?
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6. The Membrane
Biological Membranes
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How does the inclusion of cholesterol affect animal cell membranes?
A
It causes the membrane to become rigid and brittle at all temperatures.
B
It has no significant effect on membrane properties.
C
It makes the membrane completely impermeable to all molecules.
D
It increases membrane fluidity at low temperatures and decreases fluidity at high temperatures.
Verified step by step guidance1
Understand the structure of cholesterol: Cholesterol is a lipid molecule with a hydrophobic tail and a hydrophilic hydroxyl group. It is embedded within the phospholipid bilayer of animal cell membranes.
Recognize the role of cholesterol at low temperatures: At low temperatures, cholesterol prevents the phospholipids in the membrane from packing too closely together, which helps maintain membrane fluidity and prevents the membrane from becoming too rigid.
Understand the role of cholesterol at high temperatures: At high temperatures, cholesterol interacts with the phospholipids to restrict their movement, reducing excessive fluidity and stabilizing the membrane.
Learn why cholesterol does not make the membrane impermeable: Cholesterol modulates fluidity but does not block the movement of all molecules. Membrane permeability is influenced by other factors, such as the presence of transport proteins and the size/polarity of molecules.
Conclude the dual role of cholesterol: Cholesterol acts as a buffer for membrane fluidity, increasing fluidity at low temperatures and decreasing fluidity at high temperatures, ensuring the membrane remains functional across a range of conditions.
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