Multiple Choice
The rate of transfer across a membrane is measured for a given molecule. The diffusion rate is seen to be hyperbolic with respect to the concentration of the diffusing molecule. The method of transport is which of the following?
11. Biological Membranes and Transport
Passive Membrane Transport
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The rate of movement (flux) of a substance X into cells was measured at different concentrations of X to construct the following graph. Does the graph's data suggest diffusion of X into cells is mediated by a protein transporter?
A
Yes, diffusion of X is mediated by a protein transporter (facilitated diffusion).
B
No, diffusion of X is not mediated by a protein transporter (simple diffusion).
Verified step by step guidance1
Examine the graph provided, which plots the flux of substance X against its concentration [X].
Identify the relationship between flux and concentration. In this graph, the relationship appears to be linear, as indicated by the straight line.
Understand that a linear relationship between flux and concentration suggests that the rate of movement of X is directly proportional to its concentration.
Recall that simple diffusion is characterized by a linear relationship between flux and concentration, as it depends solely on the concentration gradient.
Conclude that since the graph shows a linear relationship, the diffusion of X is likely not mediated by a protein transporter, which would typically show a hyperbolic curve due to saturation kinetics, indicative of facilitated diffusion.
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