DP Biology (first assessment 2025)

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Question 21N.1A.HL.TZ1.6

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Date November 2021 Marks available [Maximum mark: 1] Reference code 21N.1A.HL.TZ1.6
Level HL Paper 1A Time zone TZ1
Command term Question number 6 Adapted from N/A
6.
[Maximum mark: 1]
21N.1A.HL.TZ1.6

The image shows the structure of the protein hemoglobin

[Source: Hemoglobin molecule, Microbiology ID: [email protected] OpenStax Microbiology
https://cnx.org/contents/[email protected] and https://commons.wikimedia.org/wiki/File:OSC_Microbio_07_04_
hemoglobin.jpg Licensed under a Creative Commons Attribution 4.0 International License,
https://creativecommons.org/licenses/by/4.0.]

 

What level of protein structure bonds the α and β chains together?

A. Primary

B. Secondary

C. Tertiary

D. Quaternary

[1]

Markscheme

D

Examiners report

This question proved surprisingly challenging. The linking together of polypeptides in a hemoglobin molecule is quaternary structure. A misreading of the question might have led to the answer ‘primary structure’ as that is the bonding together within polypeptides, but few candidates chose that answer and many more chose secondary or tertiary structure. Perhaps ‘binds’ rather than ‘bonds’ in the question would have helped avoid misunderstandings.

Syllabus sections