The reaction below occurs during aerobic respiration. The reaction is catalysed by the enzyme succinate dehydrogenase.

a. Name the substrate in this reaction.

b. The molecule malonic acid, which is shown here, inhibits this reaction. It does not bind permanently to the enzyme. Describe how malonic acid inhibits the enzyme succinate dehydrogenase.

c. Heavy metals such as lead and mercury bind permanently to –SH groups of amino acids present in enzymes. These –SH groups could be in the active site or elsewhere in the enzyme.

i. Name the amino acid which contains –SH groups.

ii. Explain the function of –SH groups in proteins and why binding of heavy metals to these groups would inhibit the activity of an enzyme. [4]

iii. What type of inhibition would be caused by the heavy metals?

Transcribed Image Text:

COOH COOH CH, succinate dehydrogenase CH CH, CH COOH COOH succinic acid fumaric acid