Proteins and Amino Acids MCQ Questions and Answers:

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

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

10． Which of the following amino acids is not contained in protein molecules?

A. cysteine ​​

B. Methionine 

C. cystine 

D. Citrulline

Answer: D 

11. Sulfur-containing amino acids include:

A. Methionine 

B．Threonine 

C. Histidine 

D. Cysteine

Answer: AD

            ​​

12. Which of the following are basic amino acids:

A. Histidine 

B. Methionine 

C. Arginine 

D. Lysine

Answer: ACD

13. Aromatic amino acids are:

A. Phenylalanine 

b. Tyrosine 

C. Tryptophan 

D. Proline

Answer: ABD

14. 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

15 . The secondary structure of proteins includes:

A. α-helix 

B. β-sheet 

C. β-turn 

D. Random curl

Answer: ABCD

16. 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

17. 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

18. 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

19. 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

20. 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

II. Fill in the blanks

1. The main elements that makeup protein are _________, ________, _________, _________.

Answer: Carbon Hydrogen Nitrogen

2. The ________ content of different proteins is quite similar, the average content is ________%.

Answer: Nitrogen 16

3. Proteins have zwitterionic properties, and most of them carry a ________ charge in acidic solutions and a _______ charge in alkaline solutions. When a protein is in a solution with a certain pH value, the number of positive and negative charges it carries is the same. At this time, the protein becomes_________, and the pH value of the solution is called the __________ of the protein.

Answer: Positive,  negative, zwitterions, Isoelectric point

4. The primary structure of a protein refers to the ____________ in the polypeptide chain.

Answer: Amino acid sequence