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.
Related Questions
Which type of molecule is LEAST likely to cross a cell membrane by simple diffusion?
Small, nonpolar molecule
Small, polar molecule
Large, polar molecule
Small, uncharged molecule
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 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
An example of facilitated diffusion is the transport of:
Oxygen across the cell membrane
Carbon dioxide out of cells
Glucose into cells
Water through aquaporins
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
