DP Biology (first assessment 2025)

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Question 23M.1A.SL.TZ1.27

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Date May 2023 Marks available [Maximum mark: 1] Reference code 23M.1A.SL.TZ1.27
Level SL Paper 1A Time zone TZ1
Command term Question number 27 Adapted from N/A
27.
[Maximum mark: 1]
23M.1A.SL.TZ1.27

The image shows leucyl-tRNA synthetase from Thermus thermophilus complexed with a tRNA. This tRNA-activating enzyme joins the amino acid leucine to tRNA using ATP.

Why is leucyl-tRNA synthetase not used to join the amino acid valine to tRNA?

A.  Phosphorylation of valine occurs at a later stage.

B.  Valine does not need to be activated to attach to tRNA.

C.  Leucyl-tRNA synthetase is substrate-specific.

D.  Valine has a different anticodon from leucine.

[1]

Markscheme

C

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