Biochemistry Questions and Answers – Peptides and Proteins

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This set of Biochemistry Multiple Choice Questions & Answers (MCQs) focuses on “Peptides and Proteins”.

1. During the formation of the peptide bond which of the following takes place?
a) Hydroxyl group is lost from its carboxyl group of one amino acid and a hydrogen atom is lost from its amino group of another amino acid
b) Hydrogen atom is lost from its carboxyl group of one amino acid and a hydroxyl group is lost from its amino group of another amino acid
c) Hydroxyl group is lost from its carboxyl group of one amino acid and a hydroxyl group is lost from its amino group of another amino acid
d) Hydrogen atom is lost from its carboxyl group of one amino acid and a hydrogen atom is lost from its amino group of another amino acid
View Answer

Answer: a
Explanation: The α-amino group of one amino acid acts as a nucleophile to displace the hydroxyl group of another amino acid forming a peptide bond.
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2. Peptide bond is a
a) Covalent bond
b) Ionic bond
c) Metallic bond
d) Hydrogen bond
View Answer

Answer: a
Explanation: Two amino acids are covalently joined through a substituted amide linkage called peptide bond.

3. A tripeptide has
a) 3 amino acids and 1 peptide bond
b) 3 amino acids and 2 peptide bonds
c) 3 amino acids and 3 peptide bonds
d) 3 amino acids and 4 peptide bonds
View Answer

Answer: b
Explanation: Monopeptide is a peptide containing single amino acid, dipeptide contains two amino acids joined by one peptide bond and tripeptide contains three amino acids joined by two peptide bonds.

4. The factor which does not affect pKa value of an amino acid is
a) The loss of charge in the α-carboxyl and α-amino groups
b) The interactions with other peptide R groups
c) Other environmental factors
d) Molecular weight
View Answer

Answer: d
Explanation: The loss of charge in the α-carboxyl and α-amino groups, the interactions with other peptide R groups and other environmental factors can affect the pKa.

5. Which of the following is a 39-residue hormone of the anterior pituitary gland?
a) Corticotropin
b) Glucagon
c) Insulin
d) Bradykinin
View Answer

Answer: a
Explanation: Corticotropin is a 39-residue hormone of the anterior pituitary gland that stimulates the adrenal cortex.
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6. The average molecular weight of an amino acid residue in a protein is about
a) 128
b) 118
c) 110
d) 120
View Answer

Answer: c
Explanation: The average molecular weight of an amino acid residue is nearer to 128. Because a molecule of water is removed to create each peptide bond, average molecular weight is 128 – 18 = 110.

7. Which of the following is not the classified form of conjugated proteins?
a) Lipoproteins
b) Glycoproteins
c) Metalloproteins
d) Complete proteins
View Answer

Answer: d
Explanation: On the basis of the chemical nature of their prosthetic groups conjugated proteins are classified into lipoproteins, glycoproteins and metalloproteins.

8. Which part of the amino acid gives it uniqueness?
a) Amino group
b) Carboxyl group
c) Side chain
d) None
View Answer

Answer: c
Explanation: Different amino acids contain different side chains which makes them unique.

9. Which of the following information is responsible to specify the three-dimensional shape of a protein?
a) The protein’s peptide bond
b) The protein’s amino acid sequence
c) The protein’s interaction with other polypeptides
d) The protein’s interaction with molecular chaperons
View Answer

Answer: b
Explanation: The amino acid sequence of a protein determines its three dimensional shape.

10. Unfolding of a protein can be termed as
a) Renaturation
b) Denaturation
c) Oxidation
d) Reduction
View Answer

Answer: b
Explanation: The proteins lose their quaternary, tertiary, secondary structure and return to its native state by denaturation process.
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11. What are the following is not a factor responsible for denaturation of proteins?
a) pH change
b) Organic solvents
c) Heat
d) Charge
View Answer

Answer: d
Explanation: pH change, organic solvents and heat are the factors responsible for denaturation of proteins.

Sanfoundry Global Education & Learning Series – Biochemistry.

To practice all areas of Biochemistry, here is complete set of 1000+ Multiple Choice Questions and Answers.

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn