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A researcher is studying facilitated diffusion of a novel solute 'X' across a cell membrane using an artificial lipid bilayer system. They observe that increasing the concentration of X on one side of the membrane increases the rate of transport, but only up to a certain point. Beyond this point, further increases in X concentration do not affect the transport rate. Which of the following BEST explains this observation?
The membrane has reached its maximum permeability for X.
The solute X is being actively transported at higher concentrations.
Saturation of the carrier proteins
The solute X is inhibiting its own transport through feedback regulation.
In a hypothetical cell, the facilitated diffusion of a solute 'Y' is observed to be significantly faster than predicted by simple diffusion models. However, the transport rate plateaus at high concentrations of Y. Which of the following is the MOST likely explanation for this observation?
The cell membrane is selectively permeable to Y.
The solute Y is transported via carrier proteins.
The solute Y is undergoing active transport.
The cell is modifying Y during transport.
Which of the following statements regarding facilitated diffusion is INCORRECT?
It requires transport proteins.
It is a passive process and does not require energy.
It can move molecules against their concentration gradient.
Transport proteins involved can become saturated.
The transport of glucose into most animal cells occurs via:
Simple diffusion
Facilitated diffusion using channel proteins
Facilitated diffusion using carrier proteins
Active transport
Which factor does NOT influence the rate of facilitated diffusion?
The concentration gradient of the transported substance
The number of carrier proteins in the membrane
The amount of ATP available
The temperature
In facilitated diffusion, saturation occurs when:
The concentration gradient disappears.
All carrier proteins are occupied by the transported substance.
The cell runs out of ATP.
The temperature decreases significantly.
Facilitated diffusion is different from simple diffusion because it:
Moves molecules against the concentration gradient
Uses carrier proteins
Requires ATP
Occurs only in plant cells
What happens to the rate of facilitated diffusion as the concentration of the transported molecule increases?
It increases linearly
It decreases
It reaches a maximum rate (saturation)
It remains constant
In facilitated diffusion, the carrier protein:
Hydrolyzes ATP to move the molecule
Undergoes a conformational change to transport the molecule
Forms a channel that remains permanently open
Transports molecules against their concentration gradient
What are the aquaporins in facilitated diffusion process?
Membrane proteins
Carrier proteins
Channel proteins
Carrier lipids
