CHEM 219 Principles of Organic Chemistry: Nucleic Acids, Proteins,
Enzymes, and Metabolism 2026/2027 UPDATE
1. Which of the following components is NOT part of a standard nucleotide?
A. A nitrogenous base
B. A pentose sugar
C. A fatty acid chain
D. A phosphate group
Answer: C
Rationale: A nucleotide consists of a nitrogenous base, a five-carbon sugar, and at least one
phosphate group. Fatty acids are components of lipids.
2. In a DNA double helix, how many hydrogen bonds form between Guanine
and Cytosine?
A. 1
B. 2
C. 4
D. 3
Answer: D
Rationale: Guanine and Cytosine form three hydrogen bonds, while Adenine and Thymine
form two.
,3. What type of bond links the 5’ phosphate of one nucleotide to the 3’ hydroxyl
of another in a nucleic acid chain?
A. Phosphodiester bond
B. Glycosidic bond
C. Peptide bond
D. Hydrogen bond
Answer: A
Rationale: The backbone of DNA and RNA is formed by phosphodiester bonds between the
3’ and 5’ carbons of adjacent sugars.
4. Which nitrogenous base is found in RNA but not in DNA?
A. Thymine
B. Adenine
C. Uracil
D. Cytosine
Answer: C
Rationale: RNA uses Uracil (U) instead of Thymine (T), which is found in DNA.
5. Which of the following is a purine base?
A. Cytosine
B. Adenine
C. Uracil
D. Thymine
Answer: B
Rationale: Adenine and Guanine are purines (two-ring structures); Cytosine, Thymine, and
Uracil are pyrimidines (single-ring).
, 6. The ‘antiparallel’ nature of DNA refers to:
A. The base pairing of A with T
B. The opposite 5’ to 3’ directions of the two strands
C. The twisting of the helix
D. The presence of sugar-phosphate backbones
Answer: B
Rationale: Antiparallel means one strand runs 5’ to 3’ while the other runs 3’ to 5’.
7. What is the sugar component found in RNA?
A. Deoxyribose
B. Glucose
C. Fructose
D. Ribose
Answer: D
Rationale: RNA contains Ribose, which has a hydroxyl group at the 2’ position, unlike
Deoxyribose in DNA.
8. Which amino acid does not possess a chiral center at the alpha-carbon?
A. Alanine
B. Glycine
C. Leucine
D. Valine
Answer: B
Rationale: Glycine’s R-group is a hydrogen atom, making the alpha-carbon bonded to two
hydrogens and thus achiral.
Enzymes, and Metabolism 2026/2027 UPDATE
1. Which of the following components is NOT part of a standard nucleotide?
A. A nitrogenous base
B. A pentose sugar
C. A fatty acid chain
D. A phosphate group
Answer: C
Rationale: A nucleotide consists of a nitrogenous base, a five-carbon sugar, and at least one
phosphate group. Fatty acids are components of lipids.
2. In a DNA double helix, how many hydrogen bonds form between Guanine
and Cytosine?
A. 1
B. 2
C. 4
D. 3
Answer: D
Rationale: Guanine and Cytosine form three hydrogen bonds, while Adenine and Thymine
form two.
,3. What type of bond links the 5’ phosphate of one nucleotide to the 3’ hydroxyl
of another in a nucleic acid chain?
A. Phosphodiester bond
B. Glycosidic bond
C. Peptide bond
D. Hydrogen bond
Answer: A
Rationale: The backbone of DNA and RNA is formed by phosphodiester bonds between the
3’ and 5’ carbons of adjacent sugars.
4. Which nitrogenous base is found in RNA but not in DNA?
A. Thymine
B. Adenine
C. Uracil
D. Cytosine
Answer: C
Rationale: RNA uses Uracil (U) instead of Thymine (T), which is found in DNA.
5. Which of the following is a purine base?
A. Cytosine
B. Adenine
C. Uracil
D. Thymine
Answer: B
Rationale: Adenine and Guanine are purines (two-ring structures); Cytosine, Thymine, and
Uracil are pyrimidines (single-ring).
, 6. The ‘antiparallel’ nature of DNA refers to:
A. The base pairing of A with T
B. The opposite 5’ to 3’ directions of the two strands
C. The twisting of the helix
D. The presence of sugar-phosphate backbones
Answer: B
Rationale: Antiparallel means one strand runs 5’ to 3’ while the other runs 3’ to 5’.
7. What is the sugar component found in RNA?
A. Deoxyribose
B. Glucose
C. Fructose
D. Ribose
Answer: D
Rationale: RNA contains Ribose, which has a hydroxyl group at the 2’ position, unlike
Deoxyribose in DNA.
8. Which amino acid does not possess a chiral center at the alpha-carbon?
A. Alanine
B. Glycine
C. Leucine
D. Valine
Answer: B
Rationale: Glycine’s R-group is a hydrogen atom, making the alpha-carbon bonded to two
hydrogens and thus achiral.
