Multiple Choice
Facilitated diffusion across a biological membrane requires:
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6. The Membrane
Passive vs. Active Transport
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Facilitated diffusion is used to transport which of the following across the cell membrane?
A
Water via simple diffusion
B
Large or polar molecules such as glucose
C
Small nonpolar molecules like oxygen
D
Ions against their concentration gradient
Verified step by step guidance1
Step 1: Begin by understanding the concept of facilitated diffusion. Facilitated diffusion is a type of passive transport that moves molecules across the cell membrane with the help of transport proteins, without requiring energy.
Step 2: Recognize the types of molecules that typically require facilitated diffusion. These are usually large molecules or polar molecules that cannot easily pass through the hydrophobic lipid bilayer of the cell membrane.
Step 3: Compare the options provided in the problem. Water can move via simple diffusion (osmosis), small nonpolar molecules like oxygen can diffuse directly through the membrane, and ions against their concentration gradient require active transport, not facilitated diffusion.
Step 4: Identify the correct answer based on the characteristics of facilitated diffusion. Large or polar molecules, such as glucose, require transport proteins to move across the membrane because they cannot diffuse directly through the lipid bilayer.
Step 5: Conclude that facilitated diffusion is specifically used for transporting large or polar molecules, such as glucose, across the cell membrane.
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