Biochemistry MCQ Pdf:
1. The average nitrogen content of various proteins is about_______
A．0.6%
B. 6%
C. 16%
D．26%
E．36%
Answer: C
2. The amino acids that makeup proteins are______
A．20 kinds of
B．300 kinds
C．12 kinds
D．16 kinds of
E．18 types
Answer: A
3. The protein content of the human body is approximately
A．30,000 kinds of
B．100,000 kinds of
C．1 million species
D．1 billion species
E. 10 billion species
Answer: B
4. Amino acids without asymmetric carbon atoms are
A．proline
B. Glycine
C. Cysteine
D. Serine
E．Methionine
Answer: B
5. Amino acids that form disulfide bonds in proteins are
A．Glycine
B. Serine
C. Cysteine
D. Histidine
E．Lysine
Answer: C
6. The amino acids that makeup protein molecules are
A．L-β-amino acid
B. D-β-amino acid
C. L-α-amino acid
D．D-α-amino acid
E. L, D-α-amino acid
Answer: C
7. Which of the following is a basic amino acid
A．glutamic acid
B. Serine
C. Tyrosine
D．Lysine
E．threonine
Answer: D
8. Amino acids with two carboxyl groups are
A．Serine
B. Lysine
C．Tyrosine
D．Threonine
E. glutamic acid
Answer: E
9. What makes albumin (isoelectric point 4.7) positively charged in the following pH solutions is
A．PH4.0
B．PH5.0
C．PH6.0
D．PH7.0
E．PH8.0
Answer: A
10. Most of the pI of plasma proteins are pH 5-6, and their main form in the blood is
A．Zwitterionic
B. non-polar molecules
C. Positively charged
D. Negatively charged
E. Hydrophobic molecule
Answer: D
11. Which statement about glutathione is true
A．As an active polypeptide
B. The molecule contains cystine
C. The leading functional group is hydroxyl
D．An important reducing agent in the body
E. important oxidant in the body
Answer: D
12. The composition of the main chain backbone in the polypeptide chain is
A．－NCCNCCNCCNCC－
B．－CONHCONHCONH－
C．-CHNOCHNOCHNO-
D．-CNOHCNOHCONH-
E. -CNHOCNHOCNHO-
Answer: A
13. Which of the following concepts has nothing to do with protein secondary structure
A．Irregular curl
B. Subunit
C. β-rotation angle
D. β-sheet
E. α-helix
Answer: B
14. Protein secondary structure does not include
A．α-helix
B. α-double helix
C. β-rotation angle
D. β-sheet
E. random curl
Answer: B
15. Both α-helices and β-sheets in protein molecules belong to
A．Primary structure
B. Secondary structure
C. Tertiary structure
D. Four-level structure
E. domain structure
Answer: B
16. Chemical bonds that do not directly participate in maintaining the secondary structure of proteins are
A．Hydrophobic bond
B. hydrogen bond
C. salt bond
D. Disulfide bond
E. peptide bond
Answer: E
17. Chemical bonds that can be broken when proteins are denatured do not include
A．Hydrophobic bond
B. hydrogen bond
C. salt bond
D. Disulfide bond
E. peptide bond
Answer: E
18. protein denaturation due to
A．A change in the primary structure of the protein
B. Depolymerization of protein groups
C. Disruption of spatial protein conformation
D．The loss of prosthetic group
E. protein hydrolysis
Answer: C
19. The structure unchanged when the protein is denatured is
A．Primary structure
B. Secondary structure
C. Tertiary structure
D. Four-level structure
E. domain
Answer: A
20. The main characteristic of denatured protein is
A．Not easily hydrolyzed by proteases
B. Decreased molecular weight
C. increased solubility
D．Loss of biological activity
E. covalent bond is broken
Answer: D
21. Which of the following reagents can open disulfide bonds in proteins
A．Cyanogen bromide
B. 2,4-Dinitrobenzene
C. β-mercaptoethanol
D. Iodoethanol
E. trichloroacetic acid
Answer: C
22. The main component in the protein molecule that causes the absorption of 280nm wavelength ultraviolet light is
A．The carboxyl group of glutamic acid
B. The phenyl ring of phenylalanine
C. indole ring of tryptophan
D．Peptide bond
E. SH group of cysteine
Answer: C
23. The main form of mixed amino acids in solution under neutral conditions is
A．Has a unit-positive charge
B. Has a unit negative charge
C. amphoteric ion
D. Nonpolar molecules
E. Hydrophobic molecule
Answer: B
24. The directionality of the peptide chain of a protein is
A．From N-terminal to C-terminal
B. From 5′ to 3′
C. From C-terminal to N-terminal
D．From 3′ end to 5′ end
E. none of the above
Answer: A
25． Molecules that cause abnormalities after gene mutations in “molecular diseases” are
A．protein
B. Nucleic acid
C. sugar
D. Lipids
E. vitamins
Answer: A
26. In 1926, JB Sumner of the United States first obtained the crystallization of enzymes from sword beans and confirmed that enzymes are proteins.
A: Urease
B: Pepsin
C: Trypsin
D: Chymotrypsin
Answer: A
27. In 1955, British biochemist Sanger determined the determination structure of the primary system and won the 1958 Nobel Prize in Chemistry.
A: Bovine insulin
B: Urease
C: Ribozyme
D: Chymotrypsin
Answer: A
28. Which of the following sugars has no reducing properties
A: Maltose
B: Sucrose
C: Glucose
D: Fructose
Answer: D
29. The most abundant lipid in biological membranes is
A: Phospholipid
B: Cholesterol
C: Glycolipid
D: Triacylglycerol
Answer: A
30. What is the molecular composition of sphingolipids
A: One molecule of fatty acid, one molecule of sphingosine or its derivatives, one molecule of polar alcohol
B: one molecule of fatty acid, one molecule of glycerin, one molecule of phosphoric acid, and choline
C: three molecules of fatty acid, one molecule of glycerin
D: two molecules of fatty acid, One molecule of glycerin, and one molecule of sugar
Answer: A