Answer:
The correct answer is:
This means that increasing the concentration of the substrate would increase the rate of the reaction in the presence of a competitive inhibitor, while it would not have an effect on the reaction rate in the presence of a noncompetitive inhibitor.
Explanation:
Competitive inhibitors as the word implies "compete" with substrate for the active site of the enzyme. The active site of an enzyme is a region on the enzyme made up of proteins that are complementary to the attachment mechanism of either the substrate or the inhibitor. Inhibitors have similar structural composition with substrates especially at the attachment sites, hence is capable of binding to the active site of the enzyme, hence competitive inhibition occurs, because the desired chemical reaction that is supposed to occur when enzyme comes in contact with substrate do not occur on the enzyme bound to the inhibitor.
At any one time, en enzyme can be bound reversibly to the substrate, the inhibitor, or neither, but never both, hence, increasing the number of the substrate, will increase the probability of the substrate making contact with the active site of the enzyme, because the inhibitors will be outnumbered.
On the other hand, for noncompetitive inhibition, the inhibitor binds to another site on the enzyme other than the active site, hence causing a structural distortion in the enzyme that makes the active site on the enzyme unable to bind to the substrate. Because this competition, has nothing to do with the active site directly, even though the number of substrates are increased, no change will be seen in the rate of reaction, because the inhibitor will still be bound to the alternative site on the enzyme, making the enzymes practically useless in the situation.
Note also, that there is a third type of inhibition called uncompetitive inhibition. Here, the inhibitor binds to the enzyme-substrate complex (E-S), producing an Enzyme-substrate-inhibitor (E-S-I) complex. This E-S-I complex formation, reduces the rate at which product is formed or at which the substrate leaves the active site then reducing reaction rate.
