The binding of a compound to an enzyme is observed to slow down or stop the rate

Question

The binding of a compound to an enzyme is observed to slow down or stop the rate of the reaction catalyzed by the enzyme. Increasing the substrate concentration reduces the inhibitory effects of this compound. Which of the following could account for this observation?

a)The compound reduces disulfide bonds, causing the enzyme molecules to partially unfold.
b)The compound causes a cofactor to be lost from the enzyme.
c)The compound forms a covalent bond with one of the amino acid residues needed for enzyme activity.
d)The compound is a negative allosteric regulator.
e)The compound is a competitive inhibitor.

Explanation / Answer

Answer : b,d,e e)If the compound is a competitive inhibitor ofthe enzyme, it would bind to the enzyme at the site at which the substrate usually binds, thus preventing the substrate from binding and either slowing or completely preventing the reaction catalyzed by the enzyme. d) In allosteric regulation, the compound binds to a site, other than the active site on the enzyme (the allosteric site). This can either cause an increase or decrease in the enzymes activity. In the case of negative allosteric regulation, the binding of the compound will reduce the enzymes activity and hence slow down the rate of the reaction b) A cofactor is a non-protein chemical compound that must bind to the enzyme in order for it to carry out it's biological activity. Cofactors are ofter metal atoms, such as heme in haemoglobin. It is possible that a compound could displace the cofactor from the enzyme, thus stopping the reaction the enzyme catalyses.

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