A R I Z O N A S TAT E U N I V E R S I T Y · S C H O O L O F L I F E S C I E N C E S
BIO 181 Exam 2
Practice Question Bank
Comprehensive Review with Rationales
Topics: DNA Replication · Protein Synthesis · Photosynthesis · Cellular
Respiration · Immune System · Digestion & More
Edition 1 · August 2026
Table of Contents
1. Instructions for Use 2
2. DNA Replication & Protein Synthesis 2
3. Photosynthesis & Cellular Respiration 3
4. Immune System & Lymphatic System 4
,5. Digestive System & Nutrition 5
6. Epithelial & Connective Tissue 6
ASU BIO 181 · Arizona State University Page 1
,ASU BIO 181 EXAM 2 PRACTICE GUIDE INSTRUCTIONS & DNA / PROTEIN
How to Use This Guide
Read each stem, choose your answer, then check the rationale directly below it. The correct
option is marked, and each wrong option is explained so you understand why it's wrong — not
just that it is. Items marked NEEDS RATIONALE had limited source detail; treat those as flags
for independent review.
DNA Replication & Protein Synthesis
1 Which enzyme is used first to permit DNA polymerase III to begin replicating the 3'
strand?
A Primase
B Helicase
C Ligase
D Topoisomerase
Why A is correct: Primase synthesizes RNA primers that provide a free 3'-OH group for
DNA polymerase III to begin DNA synthesis on the lagging strand.
B — Helicase unwinds the double helix but does not synthesize primers.
C — Ligase seals Okazaki fragments on the lagging strand after replication.
D — Topoisomerase relieves supercoiling ahead of the replication fork.
, 2 For DNA polymerase III to work, which of these components has to act first?
A DNA ligase
B Primase
C Helicase
D Topoisomerase
Why B is correct: Primase must synthesize an RNA primer to provide the free 3'-OH group
necessary for DNA polymerase III to initiate replication.
A — Ligase acts after replication to seal Okazaki fragments.
C — Helicase unwinds DNA but does not provide the primer.
D — Topoisomerase relieves supercoiling, not primer synthesis.
3 Which strand is produced more rapidly during DNA replication?
A Leading strand
B Lagging strand
C Both are produced at the same rate
D Neither — rate depends on the organism
Why A is correct: The leading strand is synthesized continuously in the same direction as
the replication fork, making it more rapid than the lagging strand, which is synthesized
discontinuously as Okazaki fragments.
B — The lagging strand is synthesized in fragments and requires more steps, making it
slower.
C — The rates differ due to the discontinuous nature of lagging strand synthesis.
D — While rates can vary, the leading strand is universally synthesized more rapidly within a
given organism.
BIO 181 Exam 2
Practice Question Bank
Comprehensive Review with Rationales
Topics: DNA Replication · Protein Synthesis · Photosynthesis · Cellular
Respiration · Immune System · Digestion & More
Edition 1 · August 2026
Table of Contents
1. Instructions for Use 2
2. DNA Replication & Protein Synthesis 2
3. Photosynthesis & Cellular Respiration 3
4. Immune System & Lymphatic System 4
,5. Digestive System & Nutrition 5
6. Epithelial & Connective Tissue 6
ASU BIO 181 · Arizona State University Page 1
,ASU BIO 181 EXAM 2 PRACTICE GUIDE INSTRUCTIONS & DNA / PROTEIN
How to Use This Guide
Read each stem, choose your answer, then check the rationale directly below it. The correct
option is marked, and each wrong option is explained so you understand why it's wrong — not
just that it is. Items marked NEEDS RATIONALE had limited source detail; treat those as flags
for independent review.
DNA Replication & Protein Synthesis
1 Which enzyme is used first to permit DNA polymerase III to begin replicating the 3'
strand?
A Primase
B Helicase
C Ligase
D Topoisomerase
Why A is correct: Primase synthesizes RNA primers that provide a free 3'-OH group for
DNA polymerase III to begin DNA synthesis on the lagging strand.
B — Helicase unwinds the double helix but does not synthesize primers.
C — Ligase seals Okazaki fragments on the lagging strand after replication.
D — Topoisomerase relieves supercoiling ahead of the replication fork.
, 2 For DNA polymerase III to work, which of these components has to act first?
A DNA ligase
B Primase
C Helicase
D Topoisomerase
Why B is correct: Primase must synthesize an RNA primer to provide the free 3'-OH group
necessary for DNA polymerase III to initiate replication.
A — Ligase acts after replication to seal Okazaki fragments.
C — Helicase unwinds DNA but does not provide the primer.
D — Topoisomerase relieves supercoiling, not primer synthesis.
3 Which strand is produced more rapidly during DNA replication?
A Leading strand
B Lagging strand
C Both are produced at the same rate
D Neither — rate depends on the organism
Why A is correct: The leading strand is synthesized continuously in the same direction as
the replication fork, making it more rapid than the lagging strand, which is synthesized
discontinuously as Okazaki fragments.
B — The lagging strand is synthesized in fragments and requires more steps, making it
slower.
C — The rates differ due to the discontinuous nature of lagging strand synthesis.
D — While rates can vary, the leading strand is universally synthesized more rapidly within a
given organism.
