DP Biology (first assessment 2025)

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Question 23M.2.HL.TZ1.b

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Date May 2023 Marks available [Maximum mark: 4] Reference code 23M.2.HL.TZ1.b
Level HL Paper 2 Time zone TZ1
Command term Explain Question number b Adapted from N/A
b.
[Maximum mark: 4]
23M.2.HL.TZ1.b

Explain the regulation of metabolic pathways by end-product inhibition.

[4]

Markscheme
  1. final product in pathway acts as an inhibitor/blocks (reaction)/slows (reaction);
  2. first/early/earlier enzyme (in pathway is inhibited);
  3. non-competitive / binds at allosteric site / causes active site to change;
  4. production of end-product reduced/paused when there is an excess;
  5. isoleucine inhibits enzyme using threonine as substrate at start of pathway to isoleucine;
  6. negative feedback / production restarts when end-product used up/concentration drops;

For mpe accept other examples of end-product inhibition if verified. Please add a note in such cases.

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