The diagram shows the structure of the protein CXCL12.

[Source: Lu, J., Chatterjee, M., Schmid, H. et al. CXCL14 as an emerging immune and inflammatory modulator.
J Inflamm 13, 1 (2016). https://doi.org/10.1186/s12950-015-0109-9 Distributed under the terms of the
Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/).]

Which chemical group is found at X?

A. NH₂

B. NOH

C. COH

D. COOH

D

The image shows the structure of the protein hemoglobin

[Source: Hemoglobin molecule, Microbiology ID: e42bd376-624b-4c0f-972f-e0c57998e765@4.4 OpenStax Microbiology
https://cnx.org/contents/5CvTdmJL@4.4 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

D

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.

Which statement applies to the tertiary structure of enzymes?

A. Tertiary structure is the sequence of amino acids in an enzyme.

B. Some enzymes do not have a tertiary structure.

C. An example of tertiary structure in an enzyme is the alpha helix.

D. A change in the tertiary structure of an enzyme may result in a change in the structure of the active site.

D

Succinate dehydrogenase is an enzyme that catalyses the oxidation of succinic acid. If malonic acid is added to the mixture, the rate of reaction is reduced. An increase in succinic acid will increase the rate of reaction again. For this system, which term best describes malonic acid?

A. Substrate

B. End product

C. Non-competitive inhibitor

D. Competitive inhibitor    

D

Which of the molecules contain peptide bonds or are sugar molecules?

B

The table shows the mass of different types of fat in some foods.

Which oil would be least recommended for inclusion in the human diet?

A. Palm oil

B. Canola oil

C. Sunflower oil

D. Partially hydrogenated soybean oil

D