DP Chemistry (last assessment 2024)

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Question 19N.3.hl.TZ0.a

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Date November 2019 Marks available [Maximum mark: 1] Reference code 19N.3.hl.TZ0.a
Level hl Paper 3 Time zone TZ0
Command term Outline Question number a Adapted from N/A
a.
[Maximum mark: 1]
19N.3.hl.TZ0.a

The Michaelis–Menten equation describes the kinetics of enzyme-catalysed reactions.

Outline the significance of the Michaelis constant Km.

[1]

Markscheme

Km is inverse measure of affinity of enzyme for a substrate
OR
Km is inversely proportional to enzyme activity
OR
high value of Km indicates higher substrate concentration needed for enzyme saturation
OR
low value of Km means reaction is fast at low substrate concentration ✔

NOTE: Idea of inverse relationship must be conveyed.
Accept “high value of Km indicates low affinity of enzyme for substrate/less stable ES complex/lower enzyme activity”.
Accept “low value of Km indicates high affinity of enzyme for substrate/stable ES complex/greater enzyme activity”.

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