HESI A2 Biology 2026 Practice Questions and
Answers with Detailed Rationales – Nursing Entrance
Exam
1. Which property of water helps organisms maintain a stable temperature?
A. Low density
B. High specific heat
C. Low polarity
D. High acidity
Answer: B. High specific heat
Rationale: Water has a high specific heat, meaning it can absorb a large amount of heat with
only a small increase in temperature. This helps organisms and ecosystems resist rapid
temperature changes.
2. Which macromolecule stores genetic information?
A. Lipids
B. Proteins
C. Nucleic acids
D. Carbohydrates
Answer: C. Nucleic acids
Rationale: DNA and RNA are nucleic acids. DNA stores hereditary information, while RNA
plays important roles in gene expression and protein synthesis.
3. What is the primary function of an enzyme?
A. Increase activation energy
B. Lower activation energy
C. Provide genetic information
D. Store ATP
Answer: B. Lower activation energy
,Rationale: Enzymes are biological catalysts. They lower the activation energy needed for a
chemical reaction, allowing the reaction to occur more rapidly without the enzyme being
permanently consumed.
4. Which organelle produces most ATP during aerobic cellular respiration?
A. Ribosome
B. Golgi apparatus
C. Mitochondrion
D. Lysosome
Answer: C. Mitochondrion
Rationale: Mitochondria contain the electron transport chain and ATP synthase. Most ATP
generated during aerobic respiration is produced through oxidative phosphorylation in the
mitochondria.
5. What is the primary carbon source used to make carbohydrates during
photosynthesis?
A. Oxygen
B. Carbon dioxide
C. ATP
D. Water
Answer: B. Carbon dioxide
Rationale: Plants obtain carbon dioxide from the atmosphere. During the Calvin cycle, carbon
dioxide is incorporated into organic molecules that can ultimately form carbohydrates.
6. Which structure controls what enters and leaves a cell?
A. Ribosome
B. Cell membrane
C. Nucleolus
D. Centrosome
Answer: B. Cell membrane
,Rationale: The plasma membrane is selectively permeable. It regulates the movement of
substances into and out of the cell.
7. What happens to an animal cell placed in a hypotonic solution?
A. It loses water
B. It gains water
C. It remains unchanged
D. It immediately divides
Answer: B. It gains water
Rationale: A hypotonic solution has a lower solute concentration than the cell. Water moves
into the cell by osmosis, potentially causing an animal cell to swell and burst.
8. Which process moves particles from high concentration to low
concentration without ATP?
A. Active transport
B. Diffusion
C. Endocytosis
D. Exocytosis
Answer: B. Diffusion
Rationale: Diffusion is passive transport. Molecules naturally move down their concentration
gradient from an area of higher concentration to an area of lower concentration.
9. Proteins are made from which monomers?
A. Nucleotides
B. Fatty acids
C. Amino acids
D. Monosaccharides
Answer: C. Amino acids
Rationale: Proteins are polymers made by linking amino acids together through peptide bonds.
, 10. Which stage of aerobic cellular respiration produces the most ATP?
A. Glycolysis
B. Citric acid cycle
C. Oxidative phosphorylation
D. Fermentation
Answer: C. Oxidative phosphorylation
Rationale: The electron transport chain establishes a proton gradient that powers ATP synthase.
This process produces most of the ATP generated during aerobic cellular respiration.
11. What is the cell's primary immediate energy currency?
A. DNA
B. ATP
C. RNA
D. Glucose
Answer: B. ATP
Rationale: ATP, or adenosine triphosphate, provides immediately usable energy for cellular
activities such as active transport, muscle contraction, and biosynthesis.
12. What is the primary purpose of glycolysis?
A. Break glucose into pyruvate
B. Produce DNA
C. Make oxygen
D. Replicate chromosomes
Answer: A. Break glucose into pyruvate
Rationale: Glycolysis occurs in the cytoplasm and breaks one glucose molecule into two
pyruvate molecules. It also produces a small amount of ATP and NADH.
13. Which waste product of aerobic respiration is exhaled by humans?
A. Glucose
B. Oxygen
Answers with Detailed Rationales – Nursing Entrance
Exam
1. Which property of water helps organisms maintain a stable temperature?
A. Low density
B. High specific heat
C. Low polarity
D. High acidity
Answer: B. High specific heat
Rationale: Water has a high specific heat, meaning it can absorb a large amount of heat with
only a small increase in temperature. This helps organisms and ecosystems resist rapid
temperature changes.
2. Which macromolecule stores genetic information?
A. Lipids
B. Proteins
C. Nucleic acids
D. Carbohydrates
Answer: C. Nucleic acids
Rationale: DNA and RNA are nucleic acids. DNA stores hereditary information, while RNA
plays important roles in gene expression and protein synthesis.
3. What is the primary function of an enzyme?
A. Increase activation energy
B. Lower activation energy
C. Provide genetic information
D. Store ATP
Answer: B. Lower activation energy
,Rationale: Enzymes are biological catalysts. They lower the activation energy needed for a
chemical reaction, allowing the reaction to occur more rapidly without the enzyme being
permanently consumed.
4. Which organelle produces most ATP during aerobic cellular respiration?
A. Ribosome
B. Golgi apparatus
C. Mitochondrion
D. Lysosome
Answer: C. Mitochondrion
Rationale: Mitochondria contain the electron transport chain and ATP synthase. Most ATP
generated during aerobic respiration is produced through oxidative phosphorylation in the
mitochondria.
5. What is the primary carbon source used to make carbohydrates during
photosynthesis?
A. Oxygen
B. Carbon dioxide
C. ATP
D. Water
Answer: B. Carbon dioxide
Rationale: Plants obtain carbon dioxide from the atmosphere. During the Calvin cycle, carbon
dioxide is incorporated into organic molecules that can ultimately form carbohydrates.
6. Which structure controls what enters and leaves a cell?
A. Ribosome
B. Cell membrane
C. Nucleolus
D. Centrosome
Answer: B. Cell membrane
,Rationale: The plasma membrane is selectively permeable. It regulates the movement of
substances into and out of the cell.
7. What happens to an animal cell placed in a hypotonic solution?
A. It loses water
B. It gains water
C. It remains unchanged
D. It immediately divides
Answer: B. It gains water
Rationale: A hypotonic solution has a lower solute concentration than the cell. Water moves
into the cell by osmosis, potentially causing an animal cell to swell and burst.
8. Which process moves particles from high concentration to low
concentration without ATP?
A. Active transport
B. Diffusion
C. Endocytosis
D. Exocytosis
Answer: B. Diffusion
Rationale: Diffusion is passive transport. Molecules naturally move down their concentration
gradient from an area of higher concentration to an area of lower concentration.
9. Proteins are made from which monomers?
A. Nucleotides
B. Fatty acids
C. Amino acids
D. Monosaccharides
Answer: C. Amino acids
Rationale: Proteins are polymers made by linking amino acids together through peptide bonds.
, 10. Which stage of aerobic cellular respiration produces the most ATP?
A. Glycolysis
B. Citric acid cycle
C. Oxidative phosphorylation
D. Fermentation
Answer: C. Oxidative phosphorylation
Rationale: The electron transport chain establishes a proton gradient that powers ATP synthase.
This process produces most of the ATP generated during aerobic cellular respiration.
11. What is the cell's primary immediate energy currency?
A. DNA
B. ATP
C. RNA
D. Glucose
Answer: B. ATP
Rationale: ATP, or adenosine triphosphate, provides immediately usable energy for cellular
activities such as active transport, muscle contraction, and biosynthesis.
12. What is the primary purpose of glycolysis?
A. Break glucose into pyruvate
B. Produce DNA
C. Make oxygen
D. Replicate chromosomes
Answer: A. Break glucose into pyruvate
Rationale: Glycolysis occurs in the cytoplasm and breaks one glucose molecule into two
pyruvate molecules. It also produces a small amount of ATP and NADH.
13. Which waste product of aerobic respiration is exhaled by humans?
A. Glucose
B. Oxygen
