Question

You are studying the enzyme kinetics of enzymes in the Kreb cycle. You add a molecule to the mixture that appears to act as a competitive inhibitor of one of the enzymes. At first, you cannot tell which enzyme is inhibited, but you can tell that it is bound to the inner mitochondrial membrane. Can you guess which Kreb cycle enzyme you have inhibited and how do you know?

Answer 1

The Krebs cycle enzyme likely inhibited is cytochrome c oxidase, due to its location on the inner mitochondrial membrane and the nature of competitive inhibition as seen with substances like cyanide.

Step-by-step explanation:

If you have identified that a molecule is acting as a competitive inhibitor of an enzyme in the Krebs cycle and it is bound to the inner mitochondrial membrane, the enzyme you have likely inhibited is cytochrome c oxidase. Cytochrome c oxidase is part of the electron transport chain, which is closely associated with the reactions of the Krebs cycle and is embedded within the inner mitochondrial membrane. This enzyme plays a crucial role in cellular respiration by facilitating the transfer of electrons and the generation of a proton gradient that is used to produce ATP. The implication of competitive inhibition here is that the inhibitor molecule is structurally similar to the natural substrate of the enzyme, allowing it to bind at the active site but not to undergo the chemical reaction necessary for electron transport. This mirrors the action of cyanide, a known competitive inhibitor of cytochrome c oxidase, which has lethal effects due to its irreversible binding and subsequent halting of cellular respiration.

Answer 2

Answer: Succinate dehydrogenase

Explanation: succinate dehydrogenase or Complex II or succinate-coenzyme Q reductase is an enzyme complex involved in citric acidic cycle, bound to the inner mitochondrial membrane of mammalian mitochondria and cell membrane of many bacterial cells. It is the only enzyme that participates in both the citric acid cycle and the electron transport chain. This enzyme catalyzes the oxidation of succinate to fumarate with the reduction of ubiquinone to ubiquinol, reaction occurs in the inner mitochondrial membrane by coupling the two reactions together.