Examine the following graph. Which of the following explains why the "line" on the graph does not continue in a linear fashion?

Question

Examine the following graph.  Which of the following explains why the "line" on the graph does not continue in a linear fashion?

Quizplus · Accepted Answer

The graph shows enzyme activity versus substrate concentration. As substrate concentration increases, so does enzyme activity up to a certain point (the point where the line becomes flat). This point is known as the saturation point, and it occurs when all of the active sites on the enzyme molecules are occupied by substrate molecules. After this point, the enzyme activity no longer increases with increasing substrate concentration, because there are no more active sites available for the substrates to bind to. Therefore, the line on the graph does not continue in a linear fashion because enzyme activity is limited by the availability of active sites on the enzyme molecules. Choice A does not explain why the line is not linear, since if all of the added substrate is bound to the enzyme, the reaction would continue at a constant rate until all of the substrate is used up. Choice C is also incorrect, since excess enzyme would not affect the linearity of the graph as long as substrate is still limiting. Choice D is not mentioned in the graph or the question stem.

Examine the Following Graph