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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.
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
Choose odd one out w.r.t. facilitated diffusion.
Highly selective
Uphill and needs ATP
Transport achieves saturation
Affected by protein inhibitors
    Consider the following statements and choose the correct answer
I.    Carrier proteins are needed by both facilitated diffusion and active transport and are sensitive to inhibitors that react with protein side chain
II.    Different types of proteins present in the membrane plays a major role in both active as well as passive transport
III.    The carrier proteins needed by facilitated and active transport are specific
IV.    There is no need of energy to pump molecule against a concentration in active transport
V.    Transport rate reaches to saturation point, when all the active proteins are used
I, II, II, IV and V
I, II and III
V, IV and I
I, II, III and V
Why the rate of diffusion of a substance along the concentration gradient does not increase continuously, while the concentration difference of the molecules across the membrane increases?
    Process of facilitated diffusion need ATP
    As concentration difference increases, molecule interfere with one another
    100% saturation of carrier protein after some time
    Transport proteins must be of channel protein type
