ClE 9700 - Topic 2.3 - Past Paper MCQS

The diagram shows a biological molecule found in cells. Which arrow labels a peptide bond?

• A
• B
• C
• D

The tertiary structure of a protein molecule is maintained by which bonds?

• A
• B
• C
• D

The protein myoglobin has a similar function to haemoglobin except myoglobin does not have a quaternary structure. Why does myoglobin not have a quaternary structure?

• A. Myoglobin has only one polypeptide chain.
• B. Myoglobin has a fibrous rather than a globular structure.
• C. Myoglobin does not contain a haem group.
• D. Myoglobin does not contain any alpha helices.

Which of the following statements about fibrous proteins is incorrect?

• A. They are very sensitive to changes in heat.
• B. They are insoluble.
• C. They are used as structural proteins.
• D. The often form long coils.

How can the quaternary structure of haemoglobin be described? 1 a specific order of amino acids 2 a globular structure 3 an a-helix 4 a dipeptide 5 four polypeptide chains connected together

• A. 5 only
• B. 2,3 and 5
• C. 1, 2 and 3
• D. 2 and 5

Which description of collagen is correct?

• A. Three collagen fibres coil around each other to form a strong, insoluble structure termed a triple helix.
• B. Both amino acids of the same polypeptide and amino acids of different polypeptides are joined by peptide bonds.
• C. The smallest amino acid, glycine, is found in a high proportion in collagen.
• D. Collagen polypeptides consist of many alpha helices in a regular spiral arrangement.

Protein X is a transport protein found dissolved in blood plasma and is used to transport different things around the body. It contains six internal disulfide bridges and has a roughly spherical shape. Protein Y is a structural protein found in the hair and nails of mammals. It is made of two alpha-helices twisted round each other to make a coiled coil. Are albumin and keratin examples of globular or fibrous proteins?

• A. Both are globular proteins
• B. Both are fibrous proteins
• C. X is globular, Y is fibrous
• D. Y is globular, X is fibrous

In protein molecules, which bonds are responsible for producing the primary, secondary and tertiary structure?

• A
• B
• C
• D

Two amino acids, both containing two carboxylic acid (-COOH) groups are illustrated below. Which labelled groups take part in the formation of a dipeptide of these amino acids?

• A. 1 and 5
• B. 2 and 3
• C. 2 and 4
• D. 1 and 4

The protein haemoglobin contains iron. What is the role of iron within the molecule?

• A. It undergoes reduction and oxidation (redox) reactions
• B. It stabilizes the quaternary structure of haemoglobin
• C. It enables haemoglobin to dissolve in red blood cells
• D. It binds oxygen to haemoglobin