This set of Structural Biology Multiple Choice Questions & Answers (MCQs) focuses on “Composition and Primary Structure of Proteins”.
1. The science which deals with the study of the molecular structure of biological macromolecules is ___________
a) Molecular biology
b) Cell biology
c) Structural biology
d) Developmental biology
View Answer
Explanation: Structural biology is the branch of life sciences concerned with the biological macromolecules. It gives complete information on the geometry of biomolecules like nucleic acids and proteins.
2. In general, the function of a particular protein depends on its ___________
a) One-dimensional structure
b) Three-dimensional structure
c) Two-dimensional structure
d) Four-dimensional structure
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Explanation: The three-dimensional structure is stabilized by weak chemical bonds rather than strong covalent bonds like peptide bonds. Hence the three-dimensional structure can easily change its conformation which decides the functionality of that particular protein.
3. Proteins are also known as __________
a) Polypeptide
b) Polyurethane
c) Polymer
d) Polyester
View Answer
Explanation: Proteins are made up of a series of amino acid residues linked together by peptide bonds. Hence proteins can also be called a polypeptide.
4. Protein was first described by ______________
a) Linus Pauling
b) Gerardus Mulder
c) Frederick Banting
d) Michel Chevreul
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Explanation: In the 18th century, Gerardus Mulder named Dutch scientist described protein for the first time. But the term “protein” was given by Jacob Berzelius named Swedish scientist. They both were chemists.
5. The Peptide bonds are formed by biochemical reaction that _____________
a) Extracts a hydrogen molecule as it joins the amino group of one amino acid to the carboxyl group of a neighbouring amino acid
b) Extracts a water molecule as it joins the amino group of one amino acid to the hydroxyl group of a neighbouring amino acid
c) Extracts a hydroxyl group as it joins the amino group of one amino acid to the carboxyl group of a neighbouring amino acid
d) Extracts an oxidane molecule as it joins the amino group of one amino acid to the carboxyl group of a neighbouring amino acid
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Explanation: Peptide is a covalent bond joining two consecutive amino acids from carbon one of one amino acid and nitrogen number two of neighbouring amino acid liberating a water (Oxidane) molecule.
6. What is the total number of proteinogenic amino acids?
a) 19
b) 20
c) 21
d) 22
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Explanation: Proteinogenic amino acids are genetically encoded amino acids. There are 22 proteinogenic amino acids, 20 standard genetic code + 2 amino acids coded by stop codons UAG and UGA.
7. What are the 9 essential amino acids?
a) H, I, L, K, M, F, T, W, V
b) H, C, Y, R, N, D, Q, E, S
c) H, I, C, M, T, E, Q, N, K
d) I, F, T, D, C, R, M, Y
View Answer
Explanation: Essential amino acids are the amino acids that the body cannot synthesize on its own and must come from food. There are 9 essential amino acids namely, histidine (H), isoleucine (I), leucine (L), lysine (K), methionine (M), phenylalanine (F), threonine (T), tryptophan (W) and valine (V).
8. Which of the following is not sulphur containing amino acid?
a) Methionine
b) Cysteine
c) Taurine
d) Proline
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Explanation: The four common sulphur containing amino acids are methionine, cysteine, homocysteine and taurine. But only methionine and cysteine are incorporated into proteins.
9. What is the total number of amino acid residues present in the first sequenced protein?
a) 840
b) 39
c) 51
d) 79
View Answer
Explanation: The first protein to be sequenced is Insulin. It is composed of two peptide chains A chain and B chain. The A chain of the protein insulin is composed of 21 amino acids and the B chain of the protein insulin is composed of 30 amino acids.
10. The primary structure of a protein always starts with the amino acid methionine.
a) True
b) False
View Answer
Explanation: Even though AUG is the start codon in eukaryotes, in most of the cases the methionine is removed during the post-transcriptional process.
11. The primary structure of a protein is strengthened by __________ bonds.
a) Covalent
b) Ionic
c) Hydrogen
d) Sulphur
View Answer
Explanation: The primary structure is held together by an amide type of covalent bond, which is made during the process of protein biosynthesis or translation.
12. The primary structure of a protein is determined by _________
a) The subunits of the ribosome
b) The t-RNA anticodon arm
c) The gene corresponding to the protein
d) The cell in which it is synthesized
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Explanation: The Deoxyribonucleic acid is transcribed into mRNA, which is later read by the ribosome in a process called translation. The final product of translation is protein.
13. Calculate the total number of peptide bonds in:
H+3NCHR1CONHCHR2CONHCHR3CONHCHR4CONHCHR5CONHCHR6CONHCHR7COO–
a) 7
b) 6
c) 8
d) 9
View Answer
Explanation: The given oligopeptideis a heptapeptide. It has six peptide bonds linking seven amino acid residues.
Sanfoundry Global Education & Learning Series – Structural Biology.
To practice all areas of Structural Biology, here is complete set of Multiple Choice Questions and Answers.
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