HESI A2 Biology Ultimate Proctored Exam
Guide – Verified Questions, Detailed Answer
Keys & Expert Rationales for Guaranteed
Success
Instructions
This document contains 80 unique biology questions designed for the HESI A2
exam. Each question includes four answer options, with the correct answer
marked and a brief rationale provided. Topics cover cell biology, DNA/RNA, ge-
netics, metabolism, body systems, and ecology. The content is formatted for PDF
generation using PDFLaTeX, ensuring clarity and originality.
Questions
1. What is the primary source of energy for Earth’s climate system?
a) Solar radiation (Correct)
b) Geothermal heat
c) Tidal forces
d) Atmospheric pressure
Rationale: Solar radiation drives Earth’s climate by providing energy for
atmospheric and oceanic processes. Geothermal heat, tidal forces, and pres-
sure play lesser roles.
2. Which organelle is responsible for protein synthesis in a eukaryotic cell?
a) Ribosome (Correct)
b) Mitochondrion
c) Golgi apparatus
d) Lysosome
Rationale: Ribosomes synthesize proteins by translating mRNA. Mitochon-
dria produce ATP, Golgi modifies proteins, and lysosomes degrade waste.
3. What is the role of DNA polymerase during DNA replication?
a) Adds nucleotides to the new strand (Correct)
b) Unwinds the DNA double helix
c) Seals nicks in the DNA backbone
d) Removes RNA primers
1
, Rationale: DNA polymerase adds nucleotides to the growing DNA strand
during replication. Helicase unwinds DNA, ligase seals nicks, and primase
removes primers.
4. In Mendelian genetics, what is the phenotypic ratio of a monohybrid cross
between two heterozygous parents?
a) 3:1 (Correct)
b) 1:2:1
c) 9:3:3:1
d) 1:1
Rationale: A monohybrid cross (Aa × Aa) yields a 3:1 phenotypic ratio (3
dominant:1 recessive) due to dominant-recessive inheritance. Other ratios
apply to different crosses.
5. What is the primary function of the Krebs cycle in cellular respiration?
a) Produce ATP directly
b) Generate electron carriers (Correct)
c) Break down glucose
d) Synthesize oxygen
Rationale: The Krebs cycle generates NADH and FADH2, electron carriers
used in the electron transport chain to produce ATP. Glycolysis breaks down
glucose, and oxygen is not synthesized.
6. Which body system regulates fluid balance and blood pressure?
a) Urinary system (Correct)
b) Nervous system
c) Endocrine system
d) Lymphatic system
Rationale: The urinary system regulates fluid balance and blood pressure
via kidney functions like filtration and hormone release. Other systems
have different primary roles.
7. In ecology, what term describes organisms that produce their own food?
a) Autotrophs (Correct)
b) Heterotrophs
c) Decomposers
d) Scavengers
Rationale: Autotrophs (e.g., plants) produce food via photosynthesis. Het-
erotrophs consume food, decomposers break down dead matter, and scav-
engers feed on carrion.
8. What molecule carries amino acids to the ribosome during protein synthe-
sis?
a) tRNA (Correct)
b) mRNA
c) rRNA
d) DNA
Rationale: tRNA transfers amino acids to ribosomes based on mRNA codons.
mRNA carries the genetic code, rRNA forms ribosomes, and DNA remains
in the nucleus.
2
Guide – Verified Questions, Detailed Answer
Keys & Expert Rationales for Guaranteed
Success
Instructions
This document contains 80 unique biology questions designed for the HESI A2
exam. Each question includes four answer options, with the correct answer
marked and a brief rationale provided. Topics cover cell biology, DNA/RNA, ge-
netics, metabolism, body systems, and ecology. The content is formatted for PDF
generation using PDFLaTeX, ensuring clarity and originality.
Questions
1. What is the primary source of energy for Earth’s climate system?
a) Solar radiation (Correct)
b) Geothermal heat
c) Tidal forces
d) Atmospheric pressure
Rationale: Solar radiation drives Earth’s climate by providing energy for
atmospheric and oceanic processes. Geothermal heat, tidal forces, and pres-
sure play lesser roles.
2. Which organelle is responsible for protein synthesis in a eukaryotic cell?
a) Ribosome (Correct)
b) Mitochondrion
c) Golgi apparatus
d) Lysosome
Rationale: Ribosomes synthesize proteins by translating mRNA. Mitochon-
dria produce ATP, Golgi modifies proteins, and lysosomes degrade waste.
3. What is the role of DNA polymerase during DNA replication?
a) Adds nucleotides to the new strand (Correct)
b) Unwinds the DNA double helix
c) Seals nicks in the DNA backbone
d) Removes RNA primers
1
, Rationale: DNA polymerase adds nucleotides to the growing DNA strand
during replication. Helicase unwinds DNA, ligase seals nicks, and primase
removes primers.
4. In Mendelian genetics, what is the phenotypic ratio of a monohybrid cross
between two heterozygous parents?
a) 3:1 (Correct)
b) 1:2:1
c) 9:3:3:1
d) 1:1
Rationale: A monohybrid cross (Aa × Aa) yields a 3:1 phenotypic ratio (3
dominant:1 recessive) due to dominant-recessive inheritance. Other ratios
apply to different crosses.
5. What is the primary function of the Krebs cycle in cellular respiration?
a) Produce ATP directly
b) Generate electron carriers (Correct)
c) Break down glucose
d) Synthesize oxygen
Rationale: The Krebs cycle generates NADH and FADH2, electron carriers
used in the electron transport chain to produce ATP. Glycolysis breaks down
glucose, and oxygen is not synthesized.
6. Which body system regulates fluid balance and blood pressure?
a) Urinary system (Correct)
b) Nervous system
c) Endocrine system
d) Lymphatic system
Rationale: The urinary system regulates fluid balance and blood pressure
via kidney functions like filtration and hormone release. Other systems
have different primary roles.
7. In ecology, what term describes organisms that produce their own food?
a) Autotrophs (Correct)
b) Heterotrophs
c) Decomposers
d) Scavengers
Rationale: Autotrophs (e.g., plants) produce food via photosynthesis. Het-
erotrophs consume food, decomposers break down dead matter, and scav-
engers feed on carrion.
8. What molecule carries amino acids to the ribosome during protein synthe-
sis?
a) tRNA (Correct)
b) mRNA
c) rRNA
d) DNA
Rationale: tRNA transfers amino acids to ribosomes based on mRNA codons.
mRNA carries the genetic code, rRNA forms ribosomes, and DNA remains
in the nucleus.
2
