Structural Biology Questions and Answers – Collagen

This set of Structural Biology Multiple Choice Questions & Answers (MCQs) focuses on “Collagen”.

1. Which of the following is both flexible and strong?
a) Alpha-helical fibres
b) Beta-sheet fibres
c) Gamma helical fibres
d) Both alpha and gamma helical fibres
View Answer

Answer: b
Explanation: The fibres which are made of beta strands will be flexible as well as strong. The reason for the strength of these fibres are the sulphur bonds which is formed between cysteine residues of the beta strands. These sulphur bridges strengthen the fibres. Since the sulphur containing amino acid residues are present in relatively small amount, beta strand fibres will be flexible.

2. Which of the following is stronger than a steel wire?
a) Hair
b) Horns
c) Spider web
d) Cotton
View Answer

Answer: c
Explanation: Spider webs are stronger than the steel wires of the same diameter. The spider web is basically a beta sheet fibre. It is stronger and flexible to hold an insect which got trapped in the web. The reason for this is the phenomenon which can be seen in vulcanised rubber. The collagen also has this potential and strength to withstand stress.

3. Collagen is formed by _____________
a) Three parallel right-handed helices
b) Three anti-parallel right-handed helices
c) Three parallel left-handed helices
d) Three anti-parallel left-handed helices
View Answer

Answer: c
Explanation: Collagen contains three left-handed helices which are parallel to each other. These helices get bundled and twisted together forming a flexible fibre. The forces involved here are H-bonds, ionic interactions and Van der Wall’s forces and rarely S-bonds.

4. Identify collagen (Note: All are left-handed helices).
a) NH3+ – – – (CHR)n – – – COO, NH3+ – – – (CHR)n – – – COO and OOC – – – (CHR)n – – – +H3N
b) OOC – – – (CHR)n – – – +H3N, NH3+ – – – (CHR)n – – – COO, NH3+ – – – (CHR)n – – – COO and OOC – – – (CHR)n – – – +H3N
c) NH3+ – – – (CHR)n – – – COO, NH3+ – – – (CHR)n – – – COO, NH3+ – – – (CHR)n – – – COO and NH3+ – – – (CHR)n – – – COO
d) NH3+ – – – (CHR)n – – – COO, NH3+ – – – (CHR)n – – – COO and NH3+ – – – (CHR)n – – – COO
View Answer

Answer: d
Explanation: We know that collagen is a bundle of three left-handed helices. It is given that each NH3+ – – – (CHR)n – – – COO represents left-handed helix. Hence, the answer should contain three such chains. Further, collagen can be formed only when these left-handed helices are parallel to each other. Hence, all the amine ends should be at one end and all the carboxyl ends at the other.

5. Which of the following doesn’t contain collagen fibres?
a) Bone
b) Extracellular space
c) Hooves
d) Tendons
View Answer

Answer: c
Explanation: The collagen can be found in extracellular space of the tissues especially of connective tissue. It is also found in bones, tendons and ligaments. The main reason for the rigidity of the bone even though it’s basic component is collagen, is the mineralisation. Tendons are also connective tissues. Hence, they are made of collagen. But hooves are made of keratins.

6. The term “Collagen” is derived from ___________ language.
a) Italian
b) Greek
c) Latin
d) Arabic
View Answer

Answer: b
Explanation: The term is derived from the Greek word “kolla” (glue) and “gen” (producing). In the 18th century, skin and tendons of some animals, especially of horses, are used to produce the glue. Skin and tendons of those animals are boiled to obtain the glue.

7. Which of the following motifs are highly repeated in collagen?
a) Glycine-Lysine-X and Glycine-X-Valine
b) Lysine-Valine-X and Lysine-X-Proline
c) Leucine-Valine-X and Leucine-X-Isoleucine
d) Glycine-Proline-X and Glycine-X-Hydroxyproline
View Answer

Answer: d
Explanation: The most common motif is a sequence of 3 amino acids such as Glycine-Proline-X where X can be any amino acid other than glycine and proline. Another most common motif is Glycine-X-Hydroxyproline where X can be any amino acid other than glycine and hydroxyproline.

8. Which amino acid that is found in collagen but absent in the majority of proteins?
a) Glycine
b) Proline
c) Hydroxyproline
d) Valine
View Answer

Answer: c
Explanation: Hydroxyproline is the rarest amino acid and is found only in some proteins. The amino acid proline is converted to hydroxyproline by an enzyme known as prolyl hydroxylase. It plays the main role in the human body since most of the connective tissues are made of collagen containing hydroxyproline. It also protects the hydroxyproline from degrading at the body temperature.

9. The three chains of collagen are __________
a) alpha 1, alpha 2 and alpha 3
b) alpha 1, alpha 2 and alpha 2
c) alpha 1, alpha 3 and alpha 3
d) alpha 1, alpha 1 and alpha 2
View Answer

Answer: d
Explanation: Collagen has 3 helical chains made of amino acids. Out of these three, two chains are similar in chemical composition and this chain is referred to as alpha 1 chain. Hence, collagen contains two alpha 1 chains. The third chain of collagen is quite different than the other two and hence it is referred to as alpha 2 chain.

10. What is the precursor of the collagen?
a) Profilaments
b) Procollagens
c) Protofilaments
d) Protocollagens
View Answer

Answer: b
Explanation: The collagen is not synthesized as a whole. The precursors assemble to form the collagen. The precursors in the formation of the collagen are procollagens. These are nothing but the peptides containing nearly 200 amino acid residues.

11. What is the standard length of a tropocollagen?
a) 2000 × 10-10
b) 5000 × 10-10
c) 6000 × 10-10
d) 3000 × 10-10
View Answer

Answer: d
Explanation: A tropocollagen is a polypeptide chain which builds collagen. And it has a length of 300 nanometers or 3000 angstroms. The chain can contain almost 1000 amino acid residues. Majority of this are glycine, proline and hydroxyproline.

12. Which type of collagen is most abundant in the human body?
a) Type 1
b) Type 2
c) Type 3
d) Type 4
View Answer

Answer: a
Explanation: The type 1 collagen can be widely seen in the human body. The type 1 collagen is the key component of the bones, tendons, ligaments, skin, vasculature and other connective tissues. About 90% of the total collagen found in the human body is type 1.

13. The superhelix of the collagen is _____________
a) Left-handed
b) Right-handed
c) Depends on the amino acid residues
d) Depends on its melting temperature
View Answer

Answer: b
Explanation: The 3 left-handed helical chains known as alpha chains get twisted together to form the collagen. But this triple helix or super helix will be always right-handed in nature even though the polypeptides participating are left-handed in conformation. And they are stabilized by hydrogen bonds.

14. The chains of collagen are held together by H-bonds.
a) True
b) False
View Answer

Answer: a
Explanation: Usually, the three polypeptide chains of collagen are held together by H-bonds. This hydrogen bond is formed between the carboxyl group of proline of one polypeptide and an amino group of the glycine of the neighbouring polypeptide.

15. Water-mediated hydrogen bonds are formed in collagen only when proline is present.
a) False
b) True
View Answer

Answer: a
Explanation: The main reason for the formation of the water-mediated hydrogen bonds is alanine. The alanine residues induce the formation of a void between the polypeptides by pushing the polypeptides apart from each other. This makes four water molecules to occupy the space between them. Hence water-mediated hydrogen bonds are formed between the chains.

Sanfoundry Global Education & Learning Series – Structural Biology.

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