Question

feedback inhibition is important for the regulation of many metabolic pathways. which of the statements are examples of feedback inhibition?
□ arsenic binds to pyruvate dehydrogenase and inhibits the enzyme.
□ the lac operon is not transcribed when there is no lactose present.
□ the production of isoleucine is halted by the presence of excess isoleucine.
□ the beginning of glycolysis is inhibited by high levels of atp in the cell.
□ the last enzyme in glycolysis is activated by the intermediates of glycolysis.

Explanation:

Feedback inhibition occurs when the end - product of a metabolic pathway inhibits an earlier step in the pathway. In the case of isoleucine production, excess isoleucine halts its own production, and high levels of ATP (end - product of energy metabolism) inhibit the start of glycolysis. Arsenic binding to an enzyme is non - feedback inhibition (it's a toxic substance binding). The lac operon regulation is related to the presence of an inducer (lactose) and not feedback inhibition. Activation of an enzyme by intermediates is not feedback inhibition.

Answer:

The production of isoleucine is halted by the presence of excess isoleucine.
The beginning of glycolysis is inhibited by high levels of ATP in the cell.