# Explain how the products of enzyme-catalysed reactions accumulate in metabolic pathways, and outline how end-product inhibition prevents the overproduction of metabolites.

> IB DP Biology Standard Level (2023 syllabus) — C1.1 Enzymes and metabolism · Explain · 4 marks

> In metabolic pathways, a series of enzyme-catalysed reactions converts an initial substrate into a final product through several intermediate steps. The final product can regulate the activity of enzymes earlier in the pathway.

## Mark scheme (4 marks)

1. In a metabolic pathway, the product of one reaction becomes the substrate for the next enzyme in the sequence.
2. When the final end-product accumulates (at high concentration), it binds to an allosteric site on an enzyme earlier in the pathway.
3. Binding of the end-product changes the shape of the active site of that enzyme, reducing its activity / preventing substrate binding.
4. This negative feedback mechanism stops further production of the end-product when it is already at sufficient concentration, preventing waste of resources / overproduction.

## Key terms

- [metabolic pathway](https://www.gradenine.co.uk/glossary/metabolic-pathway)
- [end-product inhibition](https://www.gradenine.co.uk/glossary/end-product-inhibition)

## Related

- [Revision notes for IB DP Biology Standard Level (2023 syllabus)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-the-products-of-enzyme-catalysed-a809c594) · Published by Druglandscape Ltd.