, CHEM 212 MODULE 6 EXAM
Biochemistry w/Lab
Portage Learning
100-Question Practice Examination
2026/2027 Edition
Directions: Select the best answer for each item. This original practice assessment focuses on Module 6:
Overview of Nucleic Acids..
CHEM 212 Module 6 Exam | Biochemistry w/Lab | Portage Learning | Q & A |
2026/2027 Actual (PDF)
1. A nucleotide differs from a nucleoside because a nucleotide contains which additional
component?
A) A second nitrogenous base
B) A peptide bond
C) One or more phosphate groups
D) A fatty acid tail
Correct Answer: C) One or more phosphate groups
Rationale: A nucleoside consists of a nitrogenous base attached to a pentose sugar. Adding one or more
phosphate groups produces a nucleotide. Peptide bonds link amino acids, fatty-acid tails are features of many
lipids, and a normal nucleotide does not require a second nitrogenous base.
2. Which pair contains only purine bases?
A) Uracil and cytosine
B) Adenine and guanine
C) Thymine and uracil
D) Cytosine and thymine
Correct Answer: B) Adenine and guanine
Rationale: Purines have a fused two-ring structure. Adenine and guanine are the purines found in nucleic acids.
Cytosine, thymine, and uracil are pyrimidines with a single six-membered ring, so the other pairs contain only
pyrimidines.
3. Which base is normally found in RNA in place of thymine?
A) Guanine
B) Cytosine
C) Uracil
D) Adenine
Correct Answer: C) Uracil
Rationale: RNA normally uses uracil where DNA uses thymine. Uracil can form complementary hydrogen bonds
with adenine. Guanine and cytosine are present in both DNA and RNA, while adenine is also present in both.
4. What is the sugar in DNA?
A) Ribose
B) Glucose
C) 2-deoxyribose
CHEM 212 Module 6 Practice Exam | Page 1
, D) Fructose
Correct Answer: C) 2-deoxyribose
Rationale: DNA contains 2-deoxyribose, which lacks the hydroxyl group at the 2-prime carbon that is present in
ribose. RNA contains ribose. Glucose and fructose are hexose sugars involved in other biochemical roles, not the
backbone sugars of nucleic acids.
5. The bond joining a nitrogenous base to the pentose sugar of a nucleoside is a:
A) Disulfide bond
B) beta-N-glycosidic bond
C) Phosphodiester bond
D) Peptide bond
Correct Answer: B) beta-N-glycosidic bond
Rationale: The nitrogenous base is linked to the anomeric carbon of ribose or deoxyribose by a beta-N-glycosidic
bond. Phosphodiester bonds connect adjacent nucleotides in nucleic-acid chains, peptide bonds join amino acids,
and disulfide bonds link cysteine residues in proteins.
6. Adjacent nucleotides in a DNA strand are connected primarily by:
A) Peptide bonds
B) Glycosidic bonds between bases
C) Hydrogen bonds
D) 3-prime to 5-prime phosphodiester bonds
Correct Answer: D) 3-prime to 5-prime phosphodiester bonds
Rationale: The covalent backbone of DNA is formed by phosphodiester bonds linking the 3-prime hydroxyl of one
sugar to the 5-prime phosphate of the next nucleotide. Hydrogen bonds occur mainly between complementary
bases, while glycosidic bonds attach bases to sugars.
7. Why is a nucleic-acid strand said to have polarity?
A) Every base carries a different charge
B) Only one end contains carbon atoms
C) The strand always contains unequal numbers of purines and pyrimidines
D) Its two ends have chemically distinct 5-prime and 3-prime groups
Correct Answer: D) Its two ends have chemically distinct 5-prime and 3-prime groups
Rationale: The sugar-phosphate backbone has directionality because one end is characterized by a 5-prime
group and the other by a 3-prime hydroxyl. This chemical asymmetry gives the chain polarity and is crucial for
how polymerases synthesize and read nucleic acids.
8. In standard DNA base pairing, adenine pairs with:
A) Uracil only
B) Cytosine
C) Guanine
D) Thymine
Correct Answer: D) Thymine
Rationale: In double-stranded DNA, adenine forms a complementary base pair with thymine through two
hydrogen bonds. Guanine pairs with cytosine. Uracil usually replaces thymine in RNA, so it is not the standard
partner for adenine in DNA.
9. How many hydrogen bonds are typically formed in a G-C base pair?
A) Three
B) Two
C) One
CHEM 212 Module 6 Practice Exam | Page 2
Biochemistry w/Lab
Portage Learning
100-Question Practice Examination
2026/2027 Edition
Directions: Select the best answer for each item. This original practice assessment focuses on Module 6:
Overview of Nucleic Acids..
CHEM 212 Module 6 Exam | Biochemistry w/Lab | Portage Learning | Q & A |
2026/2027 Actual (PDF)
1. A nucleotide differs from a nucleoside because a nucleotide contains which additional
component?
A) A second nitrogenous base
B) A peptide bond
C) One or more phosphate groups
D) A fatty acid tail
Correct Answer: C) One or more phosphate groups
Rationale: A nucleoside consists of a nitrogenous base attached to a pentose sugar. Adding one or more
phosphate groups produces a nucleotide. Peptide bonds link amino acids, fatty-acid tails are features of many
lipids, and a normal nucleotide does not require a second nitrogenous base.
2. Which pair contains only purine bases?
A) Uracil and cytosine
B) Adenine and guanine
C) Thymine and uracil
D) Cytosine and thymine
Correct Answer: B) Adenine and guanine
Rationale: Purines have a fused two-ring structure. Adenine and guanine are the purines found in nucleic acids.
Cytosine, thymine, and uracil are pyrimidines with a single six-membered ring, so the other pairs contain only
pyrimidines.
3. Which base is normally found in RNA in place of thymine?
A) Guanine
B) Cytosine
C) Uracil
D) Adenine
Correct Answer: C) Uracil
Rationale: RNA normally uses uracil where DNA uses thymine. Uracil can form complementary hydrogen bonds
with adenine. Guanine and cytosine are present in both DNA and RNA, while adenine is also present in both.
4. What is the sugar in DNA?
A) Ribose
B) Glucose
C) 2-deoxyribose
CHEM 212 Module 6 Practice Exam | Page 1
, D) Fructose
Correct Answer: C) 2-deoxyribose
Rationale: DNA contains 2-deoxyribose, which lacks the hydroxyl group at the 2-prime carbon that is present in
ribose. RNA contains ribose. Glucose and fructose are hexose sugars involved in other biochemical roles, not the
backbone sugars of nucleic acids.
5. The bond joining a nitrogenous base to the pentose sugar of a nucleoside is a:
A) Disulfide bond
B) beta-N-glycosidic bond
C) Phosphodiester bond
D) Peptide bond
Correct Answer: B) beta-N-glycosidic bond
Rationale: The nitrogenous base is linked to the anomeric carbon of ribose or deoxyribose by a beta-N-glycosidic
bond. Phosphodiester bonds connect adjacent nucleotides in nucleic-acid chains, peptide bonds join amino acids,
and disulfide bonds link cysteine residues in proteins.
6. Adjacent nucleotides in a DNA strand are connected primarily by:
A) Peptide bonds
B) Glycosidic bonds between bases
C) Hydrogen bonds
D) 3-prime to 5-prime phosphodiester bonds
Correct Answer: D) 3-prime to 5-prime phosphodiester bonds
Rationale: The covalent backbone of DNA is formed by phosphodiester bonds linking the 3-prime hydroxyl of one
sugar to the 5-prime phosphate of the next nucleotide. Hydrogen bonds occur mainly between complementary
bases, while glycosidic bonds attach bases to sugars.
7. Why is a nucleic-acid strand said to have polarity?
A) Every base carries a different charge
B) Only one end contains carbon atoms
C) The strand always contains unequal numbers of purines and pyrimidines
D) Its two ends have chemically distinct 5-prime and 3-prime groups
Correct Answer: D) Its two ends have chemically distinct 5-prime and 3-prime groups
Rationale: The sugar-phosphate backbone has directionality because one end is characterized by a 5-prime
group and the other by a 3-prime hydroxyl. This chemical asymmetry gives the chain polarity and is crucial for
how polymerases synthesize and read nucleic acids.
8. In standard DNA base pairing, adenine pairs with:
A) Uracil only
B) Cytosine
C) Guanine
D) Thymine
Correct Answer: D) Thymine
Rationale: In double-stranded DNA, adenine forms a complementary base pair with thymine through two
hydrogen bonds. Guanine pairs with cytosine. Uracil usually replaces thymine in RNA, so it is not the standard
partner for adenine in DNA.
9. How many hydrogen bonds are typically formed in a G-C base pair?
A) Three
B) Two
C) One
CHEM 212 Module 6 Practice Exam | Page 2
