Multiple Choice
Which of the following enhances the exchange of substances between capillary walls and the interstitial spaces?
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6. The Membrane
Biological Membranes
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How does potassium (K^+) typically move across the cell membrane in animal cells?
A
By endocytosis
B
By facilitated diffusion through potassium channels
C
By simple diffusion directly through the lipid bilayer
D
By active transport using glucose transporters
Verified step by step guidance1
Understand the nature of potassium (K^+) ions: Potassium is a charged ion, meaning it cannot pass directly through the hydrophobic lipid bilayer of the cell membrane by simple diffusion.
Review the concept of facilitated diffusion: Facilitated diffusion is a passive transport mechanism where ions or molecules move across the membrane through specific protein channels, without requiring energy input.
Identify the role of potassium channels: Potassium channels are specialized transmembrane proteins that allow the selective movement of K^+ ions across the cell membrane, following their concentration gradient.
Eliminate incorrect options: Endocytosis involves vesicle formation and is not the typical method for ion transport. Active transport requires energy (ATP) and is used to move substances against their concentration gradient, which is not the case here. Glucose transporters are specific to glucose, not potassium.
Conclude that potassium (K^+) typically moves across the cell membrane in animal cells by facilitated diffusion through potassium channels, as this matches the mechanism described.
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