Question

Consider a biochemical pathway that branches to form two different products. If the end product of one of the branches is present in a large amount, at what point would the pathway be regulated to ensure adequate production of the end product of the alternative pathway while slowing or stopping production of the product already present in excess?

1) At the very first step in the entire pathway
2) At the last step in the pathway to the product in excess
3) At the last step in the pathway to the alternative product still needed
4) At the point where the two pathways branch

Answer 1

The biochemical pathway would typically be regulated at the point where the two pathways branch, allowing for control over the production of both end products. The correct option is d.

Step-by-step explanation:

If the end product of one of the branches of a biochemical pathway is present in a large amount, the regulation of the pathway would typically occur at the point where the two pathways branch.

This is because regulating the pathway at the branching point allows the cell to direct substrate flow towards the alternative pathway, leading to the production of the other end product that is not in excess. By doing so, the pathway can efficiently balance the levels of both end products, avoiding the waste of resources and potentially harmful accumulation of one product.

Additionally, feedback inhibition is a common method of regulation where the end product of an enzyme-catalyzed reaction inhibits the activity of an enzyme earlier in the pathway, often at the first unique enzyme where the pathways differ.

Therefore, the correct option is d.