MCQ on Proteins and Amino Acids Pdf

1. The nitrogen content of a protein sample is measured to be 0.40 g. How much protein does this sample contain?
A. 2.00g
B. 2.50g
C. 6. 40g
D. 3.00g
Answer: B

Read: Nucleic Acid MCQ

2. The following amino acids contain two carboxyl groups:
A. arginine
b. Lysine
C. Glycine
D. Glutamic acid
Answer: D

3. The main chemical bonds that maintain the secondary structure of proteins are:
A. salt bond
B. Hydrophobic bond
C. peptide bond
D. Hydrogen bonds
Answer: D

4. Regarding the description of the tertiary structure of protein molecules, the wrong ones are:
A. This structure is common to natural protein molecules
B. Polypeptide chains with a tertiary structure are biologically active
C. The stability of the tertiary structure is mainly due to the maintenance of secondary bonds
D. Hydrophilic groups gather on the surface of the tertiary structure biooo
Answer: B

5. Proteins with a quaternary structure are characterized by:
A. The molecule must contain a prosthetic group
B. based on two or more polypeptide chains with tertiary structure, the peptide chains are further folded and coiled to form
C. Each polypeptide chain has independent biological activity
D. Consists of two or more polypeptide chains with tertiary structure
Answer: D

6. Colloidal particles formed by proteins are unstable under which of the following conditions:
A. The pH of the solution is greater than the pI
B. The pH of the solution is less than the pI
C. The pH of the solution is equal to the pI
D. The pH of the solution is equal to 7.4
Answer: C

7. Protein denaturation is due to:
A. A change in the sequence of amino acids
B. Changes in the amino acid composition
C. Breaking of peptide bonds
D. Disruption of protein spatial conformation
Answer: D

8. The main characteristics of denatured proteins are:
A. Decrease in viscosity
B. Increased solubility
C. Not easily hydrolyzed by proteases
D. Loss of biological activity
Answer: D

9. Which of the following amino acids is not contained in protein molecules?
A. cysteine
B. Methionine
C. cystine
D. Citrulline
Answer: D

10. Sulfur-containing amino acids include:
A. Methionine
B．Threonine
C. Histidine
D. Cysteine
Answer: AD

11. Which of the following are basic amino acids:
A. Histidine
B. Methionine
C. Arginine
D. Lysine
Answer: ACD

12. Aromatic amino acids are:
A. Phenylalanine
b. Tyrosine
C. Tryptophan
D. Proline
Answer: ABD

13. Which is correct about α-helices:
A. Every 3.6 amino acid residues in the helix is one week
B. A right-handed helical structure
C. The stability of the two helices is maintained by a disulfide bond
D. The R groups of amino acid side chains are distributed outside the helix
Answer: ABD

14. The secondary structure of proteins includes:
A. α-helix
B. β-sheet
C. β-turn
D. Random curl
Answer: ABCD

15. Which of the following statements about β-sheet structure are correct:
A. Is an extended peptide chain structure
B. Peptide bond planar folds into a zigzag
C. It can also be composed of two or more polypeptide chains arranged in forward or antiparallel
D. Ionic bonds form between the two chains to stabilize the structure
Answer: ABC

16. The central bonds that maintain the tertiary structure of proteins are:
A. peptide bond
B. Hydrophobic bond
C. ionic bond
D. Van der Waals gravity
Answer: BCD

17. Which proteins have a positive charge in solution at pH 5?
A．A protein with a pI of 4.5
B. A protein with a pI of 7.4
C. A protein with a pI of 7
D. Proteins with a pI of 6.5
Answer: BCD

18. Methods for precipitating but not denaturing proteins include:
A. Neutral salt precipitated protein
B. Tannin-precipitating protein
C. Low-temperature ethanol precipitation of protein
D. Heavy metal salt precipitation protein
Answer: AC

19. The properties of denatured proteins are:
A. Solubility decreased significantly
B. Loss of biological activity
C. Easily hydrolyzed by proteases
D. Solidification or precipitation
Answer ABC