Multiple Choice
Which of the following is an example of active transport across a cell membrane?
33
views
9. Transport Across Membranes
Principles of Transmembrane Transport
Multiple Choice
In the context of transmembrane transport, what is the main difference between simple diffusion and facilitated diffusion across a lipid bilayer?
A
Simple diffusion is saturable at high solute concentrations, whereas facilitated diffusion is not saturable.
B
Facilitated diffusion moves solutes against their concentration gradient using ATP, whereas simple diffusion moves solutes down their concentration gradient without ATP.
C
Facilitated diffusion requires specific membrane transport proteins (channels or carriers), whereas simple diffusion occurs directly through the lipid bilayer without proteins.
D
Simple diffusion occurs only for charged molecules, whereas facilitated diffusion occurs only for nonpolar molecules.
Verified step by step guidance1
Understand the basic concept of simple diffusion: it is the movement of molecules directly through the lipid bilayer from an area of higher concentration to an area of lower concentration without the assistance of proteins or energy input.
Recognize that facilitated diffusion also moves molecules down their concentration gradient but requires specific membrane transport proteins, such as channels or carrier proteins, to help molecules cross the membrane.
Note that simple diffusion is generally limited to small, nonpolar, or lipid-soluble molecules that can easily pass through the hydrophobic core of the lipid bilayer, whereas facilitated diffusion can transport larger or polar molecules that cannot cross the bilayer unaided.
Understand that facilitated diffusion is saturable because it depends on the availability of transport proteins, which can become fully occupied at high solute concentrations, while simple diffusion is not saturable as it does not rely on proteins.
Summarize the main difference: simple diffusion occurs directly through the lipid bilayer without proteins, whereas facilitated diffusion requires specific membrane transport proteins to assist the movement of solutes.
Related Videos
Related Practice
