HESI A2 BIOLOGY 2026/2027 – EXAM QUESTIONS AND
CORRECT ANSWERS (VERIFIED ANSWERS) PLUS
RATIONALE | 2027 Q&A | INSTANT DOWNLOAD PDF
1. Which statement best describes the primary purpose of metabolism in a living
organism?
A. To eliminate all waste products from the body
B. To obtain and use energy to support cellular processes
C. To prevent cells from reproducing
D. To maintain a constant number of chromosomes
Rationale: Metabolism includes the chemical reactions that obtain, transform, and use energy
and materials needed for growth, maintenance, and cellular functions. Waste removal and
chromosome regulation are important processes but do not define metabolism.
2. A student observes a specimen under a microscope and identifies a structure
surrounded by a membrane that contains genetic material and controls many
cellular activities. Which structure is being observed?
A. Ribosome
B. Lysosome
C. Golgi apparatus
D. Nucleus
Rationale: The nucleus contains most of a eukaryotic cell's DNA and regulates gene expression
and many cellular activities. Ribosomes synthesize proteins, lysosomes digest materials, and the
Golgi apparatus modifies and packages proteins.
3. Which characteristic is shared by all living organisms?
A. They use energy to carry out cellular processes.
B. They all reproduce sexually.
C. They all contain membrane-bound organelles.
D. They all obtain energy directly from sunlight.
,Rationale: All living organisms require and use energy for cellular activities. Not all organisms
reproduce sexually, prokaryotes lack membrane-bound organelles, and many organisms obtain
energy from sources other than sunlight.
4. A biological structure is composed of similar cells working together to perform a
specific function. What level of organization does this describe?
A. Organ system
B. Organism
C. Tissue
D. Organelle
Rationale: A tissue consists of a group of similar cells that work together to perform a particular
function. Several tissues can combine to form an organ.
5. Why is water particularly important to cells?
A. It permanently stores genetic information.
B. It prevents all chemical reactions from occurring.
C. It replaces the need for cellular energy.
D. It provides an effective medium for many biochemical reactions.
Rationale: Water dissolves many substances and provides the medium in which numerous
cellular reactions occur. It also contributes to temperature regulation and transport.
6. A red blood cell is placed in a solution with a lower solute concentration than the
cell's cytoplasm. What will most likely happen?
A. Water will leave the cell, causing it to shrink.
B. Water will enter the cell, causing it to swell.
C. Solute will enter until the cell becomes completely dehydrated.
D. No movement of water will occur.
Rationale: A solution with a lower solute concentration than the cell is hypotonic. Water moves
into the cell by osmosis, which can cause the cell to swell.
, 7. Which property of water allows it to form droplets and contributes to surface
tension?
A. Low specific heat
B. Nonpolarity
C. Ionization
D. Cohesion
Rationale: Cohesion is the attraction between water molecules caused by hydrogen bonding.
This attraction contributes to surface tension and allows water molecules to remain together.
8. A substance has a pH of 3. Compared with a substance having a pH of 6, the pH
3 substance has:
A. 3 times more hydrogen ions
B. 10 times fewer hydrogen ions
C. 1,000 times greater hydrogen ion concentration
D. 1,000 times lower hydrogen ion concentration
Rationale: The pH scale is logarithmic. A difference of three pH units represents a 10³, or 1,000-
fold, difference in hydrogen ion concentration. The substance with pH 3 therefore has much
more hydrogen ion concentration than the substance with pH 6.
9. Which type of biological molecule is primarily composed of amino acids?
A. Protein
B. Carbohydrate
C. Lipid
D. Nucleic acid
Rationale: Proteins are polymers made from amino acid monomers. Carbohydrates are built
from sugars, nucleic acids from nucleotides, and many lipids from fatty acids and glycerol.
10. Which carbohydrate is most directly used by cells as a major source of
immediate energy?
A. Cellulose
, B. Glycogen
C. Starch
D. Glucose
Rationale: Glucose is a simple sugar that cells can readily break down during cellular
respiration to produce ATP. Starch, glycogen, and cellulose are larger carbohydrate molecules
with different storage or structural roles.
11. A molecule contains a glycerol backbone attached to three fatty acid chains.
Which type of molecule is this?
A. Amino acid
B. Triglyceride
C. Nucleotide
D. Polysaccharide
Rationale: A triglyceride consists of one glycerol molecule bonded to three fatty acids.
Triglycerides are important for long-term energy storage and insulation.
12. Which component is characteristic of nucleic acids?
A. Glycerol
B. Peptide bonds
C. Nucleotides
D. Fatty acid chains
Rationale: DNA and RNA are nucleic acids composed of nucleotide subunits. Each nucleotide
contains a sugar, phosphate group, and nitrogenous base.
13. What is the primary function of an enzyme in a biochemical reaction?
A. Increase the amount of product permanently
B. Supply all of the energy required by the reaction
C. Change the genetic sequence of the substrate
D. Lower the activation energy required for the reaction
CORRECT ANSWERS (VERIFIED ANSWERS) PLUS
RATIONALE | 2027 Q&A | INSTANT DOWNLOAD PDF
1. Which statement best describes the primary purpose of metabolism in a living
organism?
A. To eliminate all waste products from the body
B. To obtain and use energy to support cellular processes
C. To prevent cells from reproducing
D. To maintain a constant number of chromosomes
Rationale: Metabolism includes the chemical reactions that obtain, transform, and use energy
and materials needed for growth, maintenance, and cellular functions. Waste removal and
chromosome regulation are important processes but do not define metabolism.
2. A student observes a specimen under a microscope and identifies a structure
surrounded by a membrane that contains genetic material and controls many
cellular activities. Which structure is being observed?
A. Ribosome
B. Lysosome
C. Golgi apparatus
D. Nucleus
Rationale: The nucleus contains most of a eukaryotic cell's DNA and regulates gene expression
and many cellular activities. Ribosomes synthesize proteins, lysosomes digest materials, and the
Golgi apparatus modifies and packages proteins.
3. Which characteristic is shared by all living organisms?
A. They use energy to carry out cellular processes.
B. They all reproduce sexually.
C. They all contain membrane-bound organelles.
D. They all obtain energy directly from sunlight.
,Rationale: All living organisms require and use energy for cellular activities. Not all organisms
reproduce sexually, prokaryotes lack membrane-bound organelles, and many organisms obtain
energy from sources other than sunlight.
4. A biological structure is composed of similar cells working together to perform a
specific function. What level of organization does this describe?
A. Organ system
B. Organism
C. Tissue
D. Organelle
Rationale: A tissue consists of a group of similar cells that work together to perform a particular
function. Several tissues can combine to form an organ.
5. Why is water particularly important to cells?
A. It permanently stores genetic information.
B. It prevents all chemical reactions from occurring.
C. It replaces the need for cellular energy.
D. It provides an effective medium for many biochemical reactions.
Rationale: Water dissolves many substances and provides the medium in which numerous
cellular reactions occur. It also contributes to temperature regulation and transport.
6. A red blood cell is placed in a solution with a lower solute concentration than the
cell's cytoplasm. What will most likely happen?
A. Water will leave the cell, causing it to shrink.
B. Water will enter the cell, causing it to swell.
C. Solute will enter until the cell becomes completely dehydrated.
D. No movement of water will occur.
Rationale: A solution with a lower solute concentration than the cell is hypotonic. Water moves
into the cell by osmosis, which can cause the cell to swell.
, 7. Which property of water allows it to form droplets and contributes to surface
tension?
A. Low specific heat
B. Nonpolarity
C. Ionization
D. Cohesion
Rationale: Cohesion is the attraction between water molecules caused by hydrogen bonding.
This attraction contributes to surface tension and allows water molecules to remain together.
8. A substance has a pH of 3. Compared with a substance having a pH of 6, the pH
3 substance has:
A. 3 times more hydrogen ions
B. 10 times fewer hydrogen ions
C. 1,000 times greater hydrogen ion concentration
D. 1,000 times lower hydrogen ion concentration
Rationale: The pH scale is logarithmic. A difference of three pH units represents a 10³, or 1,000-
fold, difference in hydrogen ion concentration. The substance with pH 3 therefore has much
more hydrogen ion concentration than the substance with pH 6.
9. Which type of biological molecule is primarily composed of amino acids?
A. Protein
B. Carbohydrate
C. Lipid
D. Nucleic acid
Rationale: Proteins are polymers made from amino acid monomers. Carbohydrates are built
from sugars, nucleic acids from nucleotides, and many lipids from fatty acids and glycerol.
10. Which carbohydrate is most directly used by cells as a major source of
immediate energy?
A. Cellulose
, B. Glycogen
C. Starch
D. Glucose
Rationale: Glucose is a simple sugar that cells can readily break down during cellular
respiration to produce ATP. Starch, glycogen, and cellulose are larger carbohydrate molecules
with different storage or structural roles.
11. A molecule contains a glycerol backbone attached to three fatty acid chains.
Which type of molecule is this?
A. Amino acid
B. Triglyceride
C. Nucleotide
D. Polysaccharide
Rationale: A triglyceride consists of one glycerol molecule bonded to three fatty acids.
Triglycerides are important for long-term energy storage and insulation.
12. Which component is characteristic of nucleic acids?
A. Glycerol
B. Peptide bonds
C. Nucleotides
D. Fatty acid chains
Rationale: DNA and RNA are nucleic acids composed of nucleotide subunits. Each nucleotide
contains a sugar, phosphate group, and nitrogenous base.
13. What is the primary function of an enzyme in a biochemical reaction?
A. Increase the amount of product permanently
B. Supply all of the energy required by the reaction
C. Change the genetic sequence of the substrate
D. Lower the activation energy required for the reaction
