Refer to the Graph Below, Containing Data from Three Assays

question 18

Multiple Choice

Refer to the graph below, containing data from three assays carried out simultaneously on a population of bacterial cells growing in culture.At various points in time, small samples of cells were taken from the population to measure cell number, total protein mass, and mass of enzymes involved in arginine biosynthesis.Halfway through the experiment, arginine was added to the medium in which the population was growing.A vertical arrow is shown on the graph to indicate this time. What do these data indicate about a mechanism of regulation of arginine biosynthesis in bacterial cells in response to high levels of available arginine?

• A) High levels of arginine stimulate a positive feedback regulatory mechanism.
• B) High levels of arginine stimulate a negative feedback regulatory mechanism.
• C) High levels of arginine stimulate an inhibition of gene expression.
• D) High levels of arginine stimulate an activation of enzyme covalent modification.
• E) High levels of arginine stimulate allosteric inhibition of arginine biosynthesis.

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