Question

1.In order for the electron transport chain and ATP synthase to function, the inner membrane of the mitochondrion has to be impermeable to most solutes, especially ions. Why?

2.Would you expect a competitive or a noncompetitive inhibitor to be more similar to the natural substrate of an enzyme? Why?

Answer 1

1. The inner mitochondrial membrane has to be impermeable to most of the solute specially charged ions because it is the site in mitochondria across which Proton gradient is established during electron transport chain. When electrons are transported from one electron carrier to the other, protons are also pumped from mitochondrial Matrix to intermembrane space. This results in the differential concentration of protons across inner mitochondrial membrane resulting in the formation of proton gradient. The electrochemical energy stored in Proton gradient is utilised by ATP synthase enzyme for the formation of ATP. This is called as oxidative phosphorylation.

If the inner mitochondrial membrane will not be impermeable to the ions, then Proton gradient will not be generated across the membrane and therefore ATP will not be formed.

2. Competitive inhibitor will be most similar to the substrate of an enzyme. It is because a competitive inhibitor competes for the active site of enzyme and can bind to it instead of the substrate binding to the active site. This is because the competitive inhibitor and substrate molecules are structurally similar to each other. But non-competitive inhibitor binds to the site other than the active site of enzyme and therefore is not structurally similar to the substrate molecules.

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