HESI A2 BIOLOGY EXAM (2026/2027)
QUESTIONS AND CORRECT DETAILED ANSWERS | RATED A+
NEW AND REVISED
Exam: HESI A2 Biology Section Practice Examination
Core Domains: Cellular Biology & Metabolism, DNA, RNA & Protein Synthesis, Mitosis & Meiosis,
Genetics & Heredity, Biological Macromolecules, Homeostasis & Feedback Mechanisms, Taxonomy
& Biological Organization, and Ecology & Evolution
Nursing & Healthcare Program Admissions Focus | Standardized Biology Assessment
Format
Exam Structure
The HESI A2 Biology Practice Exam for the 2026/2027 admissions cycle is a 55-question, multiple-
choice question (MCQ) examination.
Answer Format: All correct answers and biological principles are presented in bold and green,
followed by detailed rationales that explain cellular and molecular processes, apply genetic concepts,
and connect basic biology to relevant human health contexts.
1.
Which organelle is responsible for ATP production in eukaryotic cells?
A. Nucleus
B. Lysosome
C. Mitochondria
D. Golgi apparatus
Rationale: The mitochondria are known as the "powerhouse of the cell" because they generate
adenosine triphosphate (ATP) through aerobic respiration (Krebs cycle and electron transport
chain). This energy is essential for cellular functions, including muscle contraction,
nerve impulse transmission, and active transport—critical processes in human
physiology.
2.
During which phase of mitosis do sister chromatids separate and move to opposite poles?
A. Prophase
B. Metaphase
C. Anaphase
D. Telophase
Rationale: In anaphase, the centromeres split and spindle fibers pull sister chromatids apart toward
opposite poles of the cell. This ensures each daughter cell receives an identical set of
chromosomes, which is vital for growth, repair, and asexual reproduction in somatic
cells.
3.
What is the primary function of ribosomes?
, A. Lipid synthesis
B. DNA replication
C. Protein synthesis
D. Waste degradation
Rationale: Ribosomes, composed of rRNA and proteins, read mRNA during translation to assemble
amino acids into polypeptide chains. They are found free in the cytoplasm or bound to the
rough endoplasmic reticulum and are essential for producing enzymes, hormones,
and structural proteins necessary for health and disease response.
4.
Which nitrogenous base is found in RNA but not in DNA?
A. Adenine
B. Cytosine
C. Thymine
D. Uracil
Rationale: RNA uses uracil (U) instead of thymine (T) to pair with adenine. This difference
allows RNA to be more versatile in function (mRNA, tRNA, rRNA) and less stable than
DNA, which is important for temporary gene expression in protein synthesis.
5.
What type of bond holds the two strands of the DNA double helix together?
A. Covalent bonds
B. Ionic bonds
C. Hydrogen bonds
D. Peptide bonds
Rationale: Hydrogen bonds form between complementary base pairs: A=T (2 bonds) and G ≡C (3
bonds). These weak bonds allow the DNA strands to separate during replication and
transcription while maintaining structural integrity—key for genetic fidelity and
cellular function.
6.
Which process produces gametes with half the number of chromosomes as the parent cell?
A. Mitosis
B. Meiosis
C. Binary fission
D. Cytokinesis
Rationale: Meiosis reduces chromosome number from diploid (46) to haploid (23) and introduces
genetic variation through crossing over and independent assortment. This is essential for sexual
reproduction and explains inheritance patterns in genetic disorders like cystic fibrosis
or sickle cell anemia.
7.
What is the role of tRNA in protein synthesis?
A. Carries genetic code from nucleus to ribosome
B. Forms the ribosome structure
C. Brings amino acids to the ribosome based on mRNA codon
D. Unwinds the DNA helix
Rationale: Transfer RNA (tRNA) has an anticodon that matches the mRNA codon and carries the
corresponding amino acid. This ensures the correct sequence of amino acids is added to
QUESTIONS AND CORRECT DETAILED ANSWERS | RATED A+
NEW AND REVISED
Exam: HESI A2 Biology Section Practice Examination
Core Domains: Cellular Biology & Metabolism, DNA, RNA & Protein Synthesis, Mitosis & Meiosis,
Genetics & Heredity, Biological Macromolecules, Homeostasis & Feedback Mechanisms, Taxonomy
& Biological Organization, and Ecology & Evolution
Nursing & Healthcare Program Admissions Focus | Standardized Biology Assessment
Format
Exam Structure
The HESI A2 Biology Practice Exam for the 2026/2027 admissions cycle is a 55-question, multiple-
choice question (MCQ) examination.
Answer Format: All correct answers and biological principles are presented in bold and green,
followed by detailed rationales that explain cellular and molecular processes, apply genetic concepts,
and connect basic biology to relevant human health contexts.
1.
Which organelle is responsible for ATP production in eukaryotic cells?
A. Nucleus
B. Lysosome
C. Mitochondria
D. Golgi apparatus
Rationale: The mitochondria are known as the "powerhouse of the cell" because they generate
adenosine triphosphate (ATP) through aerobic respiration (Krebs cycle and electron transport
chain). This energy is essential for cellular functions, including muscle contraction,
nerve impulse transmission, and active transport—critical processes in human
physiology.
2.
During which phase of mitosis do sister chromatids separate and move to opposite poles?
A. Prophase
B. Metaphase
C. Anaphase
D. Telophase
Rationale: In anaphase, the centromeres split and spindle fibers pull sister chromatids apart toward
opposite poles of the cell. This ensures each daughter cell receives an identical set of
chromosomes, which is vital for growth, repair, and asexual reproduction in somatic
cells.
3.
What is the primary function of ribosomes?
, A. Lipid synthesis
B. DNA replication
C. Protein synthesis
D. Waste degradation
Rationale: Ribosomes, composed of rRNA and proteins, read mRNA during translation to assemble
amino acids into polypeptide chains. They are found free in the cytoplasm or bound to the
rough endoplasmic reticulum and are essential for producing enzymes, hormones,
and structural proteins necessary for health and disease response.
4.
Which nitrogenous base is found in RNA but not in DNA?
A. Adenine
B. Cytosine
C. Thymine
D. Uracil
Rationale: RNA uses uracil (U) instead of thymine (T) to pair with adenine. This difference
allows RNA to be more versatile in function (mRNA, tRNA, rRNA) and less stable than
DNA, which is important for temporary gene expression in protein synthesis.
5.
What type of bond holds the two strands of the DNA double helix together?
A. Covalent bonds
B. Ionic bonds
C. Hydrogen bonds
D. Peptide bonds
Rationale: Hydrogen bonds form between complementary base pairs: A=T (2 bonds) and G ≡C (3
bonds). These weak bonds allow the DNA strands to separate during replication and
transcription while maintaining structural integrity—key for genetic fidelity and
cellular function.
6.
Which process produces gametes with half the number of chromosomes as the parent cell?
A. Mitosis
B. Meiosis
C. Binary fission
D. Cytokinesis
Rationale: Meiosis reduces chromosome number from diploid (46) to haploid (23) and introduces
genetic variation through crossing over and independent assortment. This is essential for sexual
reproduction and explains inheritance patterns in genetic disorders like cystic fibrosis
or sickle cell anemia.
7.
What is the role of tRNA in protein synthesis?
A. Carries genetic code from nucleus to ribosome
B. Forms the ribosome structure
C. Brings amino acids to the ribosome based on mRNA codon
D. Unwinds the DNA helix
Rationale: Transfer RNA (tRNA) has an anticodon that matches the mRNA codon and carries the
corresponding amino acid. This ensures the correct sequence of amino acids is added to
