HESI A2 Biology Practice Questions 2026 –
Verified Answers and Explanations
300 Questions with Verified Answers & Detailed Rationales | Updated for 2026
300 real exam-style questions · Full rationales · Why wrong explanations · 2026 updated
Dear Future Healthcare Professional,
I remember the countless hours I spent preparing for my HESI A2 Biology exam. The anxiety of not
knowing what to expect, the frustration of finding incomplete study materials, and the determination
to succeed. After weeks of dedicated preparation, I created this comprehensive practice guide using
the exact strategies that helped me pass with flying colors.
This study guide contains the most frequently tested concepts, challenging questions that mirror the
real exam, and detailed rationales that help you understand the "why" behind each answer. I have
carefully selected and refined these questions based on what I saw on my own exam and what my
peers reported seeing on theirs.
I believe in you. Trust the process, trust your preparation, and trust yourself. You've got this!
Good luck!
HESI A2 Biology – Complete Study Guide
Verified Solutions | 2026 Updated | Graded A+
Section Topics Covered Qs Weight
Section 1 Cell Structure & Function 40 13%
Section 2 Genetics & Heredity 40 13%
Section 3 Metabolism & Energy 40 13%
Section 4 DNA & Protein Synthesis 40 13%
Section 5 Evolution & Ecology 40 13%
Section 6 Microbiology & Immunology 40 13%
Section 7 Plant Biology & Photosynthesis 30 10%
Section 8 Human Biology & Health 30 10%
What You Will Find Inside This Study Guide
Cell Structure & Function (40 Qs - 13%): Organelles, cellular transport, cell membrane, cellular respiration, and cell
division.
, Genetics & Heredity (40 Qs - 13%): Mendelian genetics, Punnett squares, inheritance patterns, genetic disorders, and
chromosomal abnormalities.
Metabolism & Energy (40 Qs - 13%): Glycolysis, Krebs cycle, electron transport chain, ATP production, and enzyme
function.
DNA & Protein Synthesis (40 Qs - 13%): DNA structure, replication, transcription, translation, mutations, and gene
expression.
Evolution & Ecology (40 Qs - 13%): Natural selection, speciation, ecosystems, food chains, biogeochemical cycles, and
population dynamics.
Microbiology & Immunology (40 Qs - 13%): Bacteria, viruses, fungi, immune response, antibodies, vaccines, and
infectious diseases.
Plant Biology & Photosynthesis (30 Qs - 10%): Photosynthesis, plant anatomy, transpiration, plant reproduction, and
plant hormones.
Human Biology & Health (30 Qs - 10%): Homeostasis, organ systems, nutrition, diseases, and health concepts.
Section 1: Cell Structure & Function (40 questions)
Q1. A patient with a rare genetic disorder has dysfunctional peroxisomes. Which of the following
metabolic processes would be most directly affected?
A Beta-oxidation of very long-chain fatty acids
B Glycolysis
C Krebs cycle
D Oxidative phosphorylation
E Fermentation
Correct answer: A. Beta-oxidation of very long-chain fatty acids
Rationale: Peroxisomes are responsible for beta-oxidation of very long-chain fatty acids. Dysfunction leads to
accumulation of these fatty acids, causing neurological symptoms.
Why wrong:
B: Glycolysis is incorrect
C: Krebs cycle is incorrect
D: Oxidative phosphorylation is incorrect
E: Fermentation is incorrect
Reference: HESI A2 Biology Study Guide · Elsevier HESI Admission Assessment Exam Review, 6th Edition.
,Q2. Which organelle is continuous with the nuclear envelope and contains ribosomes on its surface?
A Rough endoplasmic reticulum
B Smooth endoplasmic reticulum
C Golgi apparatus
D Mitochondria
E Chloroplast
Correct answer: A. Rough endoplasmic reticulum
Rationale: The rough endoplasmic reticulum is continuous with the nuclear envelope and is studded with
ribosomes for protein synthesis.
Why wrong:
B: Smooth endoplasmic reticulum is incorrect
C: Golgi apparatus is incorrect
D: Mitochondria is incorrect
E: Chloroplast is incorrect
Reference: HESI A2 Biology Study Guide · Elsevier HESI Admission Assessment Exam Review, 6th Edition.
Q3. A patient's white blood cells are unable to perform phagocytosis effectively. Which organelle is
most likely defective in these cells?
A Lysosomes
B Mitochondria
C Golgi apparatus
D Ribosomes
E Nucleus
Correct answer: A. Lysosomes
Rationale: Lysosomes contain the digestive enzymes needed to break down phagocytosed materials. Dysfunctional
lysosomes would impair phagocytosis.
Why wrong:
B: Mitochondria is incorrect
C: Golgi apparatus is incorrect
D: Ribosomes is incorrect
E: Nucleus is incorrect
Reference: HESI A2 Biology Study Guide · Elsevier HESI Admission Assessment Exam Review, 6th Edition.
, Q4. Which of the following structures is found in prokaryotic cells but not in eukaryotic cells?
A Nucleoid region
B Nucleus
C Mitochondria
D Endoplasmic reticulum
E Golgi apparatus
Correct answer: A. Nucleoid region
Rationale: Prokaryotic cells have a nucleoid region where DNA is located, but they lack a membrane-bound
nucleus. The other organelles are found in eukaryotic cells.
Why wrong:
B: Nucleus is incorrect
C: Mitochondria is incorrect
D: Endoplasmic reticulum is incorrect
E: Golgi apparatus is incorrect
Reference: HESI A2 Biology Study Guide · Elsevier HESI Admission Assessment Exam Review, 6th Edition.
Q5. A researcher is studying a cell that has an unusually high number of cristae in its mitochondria.
What can be inferred about this cell?
A It has a high demand for ATP production
B It has low metabolic activity
C It is undergoing apoptosis
D It has defective DNA replication
E It is in a dormant state
Correct answer: A. It has a high demand for ATP production
Rationale: Cristae are the folds of the inner mitochondrial membrane where the electron transport chain is
located. More cristae indicate a higher capacity for ATP production.
Why wrong:
B: It has low metabolic activity is incorrect
C: It is undergoing apoptosis is incorrect
D: It has defective DNA replication is incorrect
E: It is in a dormant state is incorrect
Reference: HESI A2 Biology Study Guide · Elsevier HESI Admission Assessment Exam Review, 6th Edition.
Verified Answers and Explanations
300 Questions with Verified Answers & Detailed Rationales | Updated for 2026
300 real exam-style questions · Full rationales · Why wrong explanations · 2026 updated
Dear Future Healthcare Professional,
I remember the countless hours I spent preparing for my HESI A2 Biology exam. The anxiety of not
knowing what to expect, the frustration of finding incomplete study materials, and the determination
to succeed. After weeks of dedicated preparation, I created this comprehensive practice guide using
the exact strategies that helped me pass with flying colors.
This study guide contains the most frequently tested concepts, challenging questions that mirror the
real exam, and detailed rationales that help you understand the "why" behind each answer. I have
carefully selected and refined these questions based on what I saw on my own exam and what my
peers reported seeing on theirs.
I believe in you. Trust the process, trust your preparation, and trust yourself. You've got this!
Good luck!
HESI A2 Biology – Complete Study Guide
Verified Solutions | 2026 Updated | Graded A+
Section Topics Covered Qs Weight
Section 1 Cell Structure & Function 40 13%
Section 2 Genetics & Heredity 40 13%
Section 3 Metabolism & Energy 40 13%
Section 4 DNA & Protein Synthesis 40 13%
Section 5 Evolution & Ecology 40 13%
Section 6 Microbiology & Immunology 40 13%
Section 7 Plant Biology & Photosynthesis 30 10%
Section 8 Human Biology & Health 30 10%
What You Will Find Inside This Study Guide
Cell Structure & Function (40 Qs - 13%): Organelles, cellular transport, cell membrane, cellular respiration, and cell
division.
, Genetics & Heredity (40 Qs - 13%): Mendelian genetics, Punnett squares, inheritance patterns, genetic disorders, and
chromosomal abnormalities.
Metabolism & Energy (40 Qs - 13%): Glycolysis, Krebs cycle, electron transport chain, ATP production, and enzyme
function.
DNA & Protein Synthesis (40 Qs - 13%): DNA structure, replication, transcription, translation, mutations, and gene
expression.
Evolution & Ecology (40 Qs - 13%): Natural selection, speciation, ecosystems, food chains, biogeochemical cycles, and
population dynamics.
Microbiology & Immunology (40 Qs - 13%): Bacteria, viruses, fungi, immune response, antibodies, vaccines, and
infectious diseases.
Plant Biology & Photosynthesis (30 Qs - 10%): Photosynthesis, plant anatomy, transpiration, plant reproduction, and
plant hormones.
Human Biology & Health (30 Qs - 10%): Homeostasis, organ systems, nutrition, diseases, and health concepts.
Section 1: Cell Structure & Function (40 questions)
Q1. A patient with a rare genetic disorder has dysfunctional peroxisomes. Which of the following
metabolic processes would be most directly affected?
A Beta-oxidation of very long-chain fatty acids
B Glycolysis
C Krebs cycle
D Oxidative phosphorylation
E Fermentation
Correct answer: A. Beta-oxidation of very long-chain fatty acids
Rationale: Peroxisomes are responsible for beta-oxidation of very long-chain fatty acids. Dysfunction leads to
accumulation of these fatty acids, causing neurological symptoms.
Why wrong:
B: Glycolysis is incorrect
C: Krebs cycle is incorrect
D: Oxidative phosphorylation is incorrect
E: Fermentation is incorrect
Reference: HESI A2 Biology Study Guide · Elsevier HESI Admission Assessment Exam Review, 6th Edition.
,Q2. Which organelle is continuous with the nuclear envelope and contains ribosomes on its surface?
A Rough endoplasmic reticulum
B Smooth endoplasmic reticulum
C Golgi apparatus
D Mitochondria
E Chloroplast
Correct answer: A. Rough endoplasmic reticulum
Rationale: The rough endoplasmic reticulum is continuous with the nuclear envelope and is studded with
ribosomes for protein synthesis.
Why wrong:
B: Smooth endoplasmic reticulum is incorrect
C: Golgi apparatus is incorrect
D: Mitochondria is incorrect
E: Chloroplast is incorrect
Reference: HESI A2 Biology Study Guide · Elsevier HESI Admission Assessment Exam Review, 6th Edition.
Q3. A patient's white blood cells are unable to perform phagocytosis effectively. Which organelle is
most likely defective in these cells?
A Lysosomes
B Mitochondria
C Golgi apparatus
D Ribosomes
E Nucleus
Correct answer: A. Lysosomes
Rationale: Lysosomes contain the digestive enzymes needed to break down phagocytosed materials. Dysfunctional
lysosomes would impair phagocytosis.
Why wrong:
B: Mitochondria is incorrect
C: Golgi apparatus is incorrect
D: Ribosomes is incorrect
E: Nucleus is incorrect
Reference: HESI A2 Biology Study Guide · Elsevier HESI Admission Assessment Exam Review, 6th Edition.
, Q4. Which of the following structures is found in prokaryotic cells but not in eukaryotic cells?
A Nucleoid region
B Nucleus
C Mitochondria
D Endoplasmic reticulum
E Golgi apparatus
Correct answer: A. Nucleoid region
Rationale: Prokaryotic cells have a nucleoid region where DNA is located, but they lack a membrane-bound
nucleus. The other organelles are found in eukaryotic cells.
Why wrong:
B: Nucleus is incorrect
C: Mitochondria is incorrect
D: Endoplasmic reticulum is incorrect
E: Golgi apparatus is incorrect
Reference: HESI A2 Biology Study Guide · Elsevier HESI Admission Assessment Exam Review, 6th Edition.
Q5. A researcher is studying a cell that has an unusually high number of cristae in its mitochondria.
What can be inferred about this cell?
A It has a high demand for ATP production
B It has low metabolic activity
C It is undergoing apoptosis
D It has defective DNA replication
E It is in a dormant state
Correct answer: A. It has a high demand for ATP production
Rationale: Cristae are the folds of the inner mitochondrial membrane where the electron transport chain is
located. More cristae indicate a higher capacity for ATP production.
Why wrong:
B: It has low metabolic activity is incorrect
C: It is undergoing apoptosis is incorrect
D: It has defective DNA replication is incorrect
E: It is in a dormant state is incorrect
Reference: HESI A2 Biology Study Guide · Elsevier HESI Admission Assessment Exam Review, 6th Edition.
