ACS BIOCHEMISTRY PRACTICE
EXAM
200 Sample Questions with
Verified Answers & Rationales
AMINO ACIDS & PROTEIN STRUCTURE
Question 1
Which amino acid contains a sulfur atom?
A. Alanine
B. Glycine
C. Methionine
D. Valine
Correct Answer: C. Methionine
Rationale:
Methionine and cysteine are the two sulfur-containing amino acids.
Question 2
Which amino acid is classified as an acidic amino acid?
A. Lysine
B. Aspartate
C. Leucine
D. Serine
Correct Answer: B. Aspartate
,Rationale:
Aspartate and glutamate contain negatively charged carboxylate side chains at physiological pH.
Question 3
The peptide bond between amino acids is formed between:
A. Two side chains
B. Amino group and carboxyl group
C. Two hydroxyl groups
D. Two sulfur groups
Correct Answer: B. Amino group and carboxyl group
Rationale:
A peptide bond forms through a condensation reaction between the amino group of one amino
acid and the carboxyl group of another.
Question 4
The primary structure of a protein refers to:
A. Three-dimensional folding
B. Amino acid sequence
C. Protein subunit arrangement
D. Hydrogen bonding pattern
Correct Answer: B. Amino acid sequence
Rationale:
Primary structure is the linear order of amino acids connected by peptide bonds.
Question 5
Secondary protein structure is stabilized mainly by:
A. Peptide bonds
B. Hydrogen bonds
C. Disulfide bonds
D. Ionic bonds only
,Correct Answer: B. Hydrogen bonds
Rationale:
Alpha helices and beta sheets are stabilized by hydrogen bonding between backbone atoms.
Question 6
The alpha helix structure is stabilized by hydrogen bonds between:
A. Side chains only
B. Backbone carbonyl and amide groups
C. Sulfur atoms
D. Carboxyl groups only
Correct Answer: B. Backbone carbonyl and amide groups
Rationale:
Hydrogen bonding between peptide backbone atoms maintains alpha helices.
Question 7
Protein denaturation generally results in loss of:
A. Primary amino acid sequence
B. Secondary and tertiary structure
C. Peptide bonds
D. Amino acid composition
Correct Answer: B. Secondary and tertiary structure
Rationale:
Denaturation disrupts higher-order structures but usually does not break peptide bonds.
Question 8
A disulfide bond forms between two residues of:
A. Glycine
B. Cysteine
C. Alanine
D. Tryptophan
, Correct Answer: B. Cysteine
Rationale:
Two cysteine sulfhydryl groups can oxidize to form a disulfide bridge.
Question 9
Which amino acid is commonly found in beta turns?
A. Proline
B. Methionine
C. Tryptophan
D. Phenylalanine
Correct Answer: A. Proline
Rationale:
Proline introduces structural bends due to its rigid ring structure.
Question 10
The amino acid tryptophan contains which functional group?
A. Indole ring
B. Sulfhydryl group
C. Guanidinium group
D. Hydroxyl group
Correct Answer: A. Indole ring
Rationale:
Tryptophan is an aromatic amino acid containing an indole ring.
ENZYMES
Question 11
Enzymes increase reaction rates by:
EXAM
200 Sample Questions with
Verified Answers & Rationales
AMINO ACIDS & PROTEIN STRUCTURE
Question 1
Which amino acid contains a sulfur atom?
A. Alanine
B. Glycine
C. Methionine
D. Valine
Correct Answer: C. Methionine
Rationale:
Methionine and cysteine are the two sulfur-containing amino acids.
Question 2
Which amino acid is classified as an acidic amino acid?
A. Lysine
B. Aspartate
C. Leucine
D. Serine
Correct Answer: B. Aspartate
,Rationale:
Aspartate and glutamate contain negatively charged carboxylate side chains at physiological pH.
Question 3
The peptide bond between amino acids is formed between:
A. Two side chains
B. Amino group and carboxyl group
C. Two hydroxyl groups
D. Two sulfur groups
Correct Answer: B. Amino group and carboxyl group
Rationale:
A peptide bond forms through a condensation reaction between the amino group of one amino
acid and the carboxyl group of another.
Question 4
The primary structure of a protein refers to:
A. Three-dimensional folding
B. Amino acid sequence
C. Protein subunit arrangement
D. Hydrogen bonding pattern
Correct Answer: B. Amino acid sequence
Rationale:
Primary structure is the linear order of amino acids connected by peptide bonds.
Question 5
Secondary protein structure is stabilized mainly by:
A. Peptide bonds
B. Hydrogen bonds
C. Disulfide bonds
D. Ionic bonds only
,Correct Answer: B. Hydrogen bonds
Rationale:
Alpha helices and beta sheets are stabilized by hydrogen bonding between backbone atoms.
Question 6
The alpha helix structure is stabilized by hydrogen bonds between:
A. Side chains only
B. Backbone carbonyl and amide groups
C. Sulfur atoms
D. Carboxyl groups only
Correct Answer: B. Backbone carbonyl and amide groups
Rationale:
Hydrogen bonding between peptide backbone atoms maintains alpha helices.
Question 7
Protein denaturation generally results in loss of:
A. Primary amino acid sequence
B. Secondary and tertiary structure
C. Peptide bonds
D. Amino acid composition
Correct Answer: B. Secondary and tertiary structure
Rationale:
Denaturation disrupts higher-order structures but usually does not break peptide bonds.
Question 8
A disulfide bond forms between two residues of:
A. Glycine
B. Cysteine
C. Alanine
D. Tryptophan
, Correct Answer: B. Cysteine
Rationale:
Two cysteine sulfhydryl groups can oxidize to form a disulfide bridge.
Question 9
Which amino acid is commonly found in beta turns?
A. Proline
B. Methionine
C. Tryptophan
D. Phenylalanine
Correct Answer: A. Proline
Rationale:
Proline introduces structural bends due to its rigid ring structure.
Question 10
The amino acid tryptophan contains which functional group?
A. Indole ring
B. Sulfhydryl group
C. Guanidinium group
D. Hydroxyl group
Correct Answer: A. Indole ring
Rationale:
Tryptophan is an aromatic amino acid containing an indole ring.
ENZYMES
Question 11
Enzymes increase reaction rates by:
