HESI A2 Biology Exam Prep Q&A (Comprehensive Practice
Questions with Explanations) Chamberlain University
This comprehensive exam prep package features curated, multiple-choice questions specifically
designed to mirror the structure and content of the HESI A2 Biology subtest. Each entry provides an
immediate verified answer alongside a detailed, bolded explanation to ensure mastery of high-yield
concepts like cellular respiration, molecular genetics, and organelle functions. Ideal for pre-nursing and
allied health students, this high-density study guide serves as an efficient resource for securing top-tier
admission scores.
Question 1
Which of the following cell organelles is primarily responsible for the synthesis of
adenosine triphosphate (ATP) via aerobic cellular respiration?
A) Golgi apparatus
B) Mitochondrion
C) Lysosome
D) Smooth endoplasmic reticulum
ANSWER: B) Mitochondrion
EXPLANATION: The mitochondrion is known as the powerhouse of the cell. It
houses the Krebs cycle and the electron transport chain, which generate the vast
majority of cellular ATP.
Question 2
What is the primary function of lysosomes within a eukaryotic cell?
A) DNA replication
B) Intracellular digestion and waste breakdown
C) Lipid synthesis
D) Protein modification
ANSWER: B) Intracellular digestion and waste breakdown
EXPLANATION: Lysosomes contain acidic hydrolytic enzymes that break down
macromolecules, worn-out organelles, and engulfed pathogens.
Question 3
Which organelle is responsible for modifying, sorting, and packaging proteins and lipids
for secretion?
A) Rough endoplasmic reticulum
B) Nucleolus
C) Golgi apparatus
D) Peroxisome
ANSWER: C) Golgi apparatus
, EXPLANATION: The Golgi apparatus functions like a cellular post office. It
receives proteins from the endoplasmic reticulum, modifies them, and packages
them into vesicles.
Question 4
A cell that specializes in producing large quantities of proteins for export would feature
an abundance of which organelle?
A) Smooth endoplasmic reticulum
B) Rough endoplasmic reticulum
C) Lysosomes
D) Centrioles
ANSWER: B) Rough endoplasmic reticulum
EXPLANATION: The rough endoplasmic reticulum is studded with ribosomes,
making it the primary site for synthesizing proteins destined for membranes or
secretion outside the cell.
Question 5
Which of the following structures is found in plant cells but completely absent in animal
cells?
A) Plasma membrane
B) Mitochondria
C) Cell wall
D) Ribosomes
ANSWER: C) Cell wall
EXPLANATION: Plant cells possess a rigid outer cell wall composed of cellulose
and chloroplasts for photosynthesis. Animal cells lack both.
Question 6
What is the main function of the nucleolus located inside the eukaryotic nucleus?
A) Storage of lipids
B) Synthesis of ribosomal RNA (rRNA)
C) Generation of spindle fibers
D) Breakdown of toxins
ANSWER: B) Synthesis of ribosomal RNA (rRNA)
EXPLANATION: The nucleolus is a dense region within the nucleus dedicated to
transcribing rRNA and assembling ribosomal subunits.
Question 7
Which organelle is responsible for lipid synthesis, carbohydrate metabolism, and drug
detoxification?
A) Rough endoplasmic reticulum
B) Smooth endoplasmic reticulum
C) Lysosome
D) Ribosome
ANSWER: B) Smooth endoplasmic reticulum
, EXPLANATION: Unlike the rough ER, the smooth ER lacks ribosomes and is
responsible for synthesizing lipids (like steroids) and detoxifying harmful
substances.
Question 8
Which of the following describes a key difference between prokaryotic and eukaryotic
cells?
A) Prokaryotic cells lack a plasma membrane.
B) Eukaryotic cells lack a true nucleus.
C) Prokaryotic cells lack membrane-bound organelles.
D) Eukaryotic cells lack ribosomes.
ANSWER: C) Prokaryotic cells lack membrane-bound organelles.
EXPLANATION: Prokaryotes (like bacteria) lack a nucleus and other membrane-
bound compartments, whereas eukaryotes possess them.
Question 9
What component of the cell membrane is primarily responsible for maintaining its fluid
nature across varying temperatures?
A) Peripheral proteins
B) Cholesterol
C) Glycoproteins
D) Nucleic acids
ANSWER: B) Cholesterol
EXPLANATION: Cholesterol acts as a fluidity buffer in the cell membrane,
preventing it from freezing in cold temperatures and becoming too fluid in hot
temperatures.
Question 10
Which organelle contains hydrogen peroxide and is responsible for breaking down long-
chain fatty acids?
A) Lysosome
B) Peroxisome
C) Ribosome
D) Vacuole
ANSWER: B) Peroxisome
EXPLANATION: Peroxisomes carry out oxidation reactions that break down fatty
acids and amino acids, producing hydrogen peroxide as a byproduct which they
then safely convert to water.
Question 11
What structure acts as the selective barrier regulating the movement of materials into
and out of a cell?
A) Cell wall
B) Nuclear envelope
C) Plasma membrane
D) Cytoskeleton
, ANSWER: C) Plasma membrane
EXPLANATION: The plasma membrane is a semi-permeable phospholipid bilayer
that controls what enters and exits the cytoplasm.
Question 12
Which cellular structure is made of actin filaments and provides mechanical support and
motility to the cell?
A) Microtubules
B) Microfilaments
C) Intermediate filaments
D) Extracellular matrix
ANSWER: B) Microfilaments
EXPLANATION: Microfilaments are the thinnest elements of the cytoskeleton,
composed of actin, and are crucial for cell movement and structural support.
Question 13
Which organelle uses solar energy to synthesize carbohydrates in photosynthetic
organisms?
A) Mitochondrion
B) Chloroplast
C) Chromoplast
D) Amyloplast
ANSWER: B) Chloroplast
EXPLANATION: Chloroplasts contain chlorophyll, which captures sunlight to
drive the synthesis of glucose from carbon dioxide and water during
photosynthesis.
Question 14
What is the function of the central vacuole in plant cells?
A) ATP generation
B) Protein translation
C) Storing water and maintaining turgor pressure
D) Replicating DNA
ANSWER: C) Storing water and maintaining turgor pressure
EXPLANATION: The large central vacuole stores water and solutes, exerting
turgor pressure against the cell wall to keep the plant upright.
Question 15
Which of the following structures is directly involved in organizing microtubules during
animal cell division?
A) Centrosome
B) Ribosome
C) Nucleus
D) Nucleoid
ANSWER: A) Centrosome
Questions with Explanations) Chamberlain University
This comprehensive exam prep package features curated, multiple-choice questions specifically
designed to mirror the structure and content of the HESI A2 Biology subtest. Each entry provides an
immediate verified answer alongside a detailed, bolded explanation to ensure mastery of high-yield
concepts like cellular respiration, molecular genetics, and organelle functions. Ideal for pre-nursing and
allied health students, this high-density study guide serves as an efficient resource for securing top-tier
admission scores.
Question 1
Which of the following cell organelles is primarily responsible for the synthesis of
adenosine triphosphate (ATP) via aerobic cellular respiration?
A) Golgi apparatus
B) Mitochondrion
C) Lysosome
D) Smooth endoplasmic reticulum
ANSWER: B) Mitochondrion
EXPLANATION: The mitochondrion is known as the powerhouse of the cell. It
houses the Krebs cycle and the electron transport chain, which generate the vast
majority of cellular ATP.
Question 2
What is the primary function of lysosomes within a eukaryotic cell?
A) DNA replication
B) Intracellular digestion and waste breakdown
C) Lipid synthesis
D) Protein modification
ANSWER: B) Intracellular digestion and waste breakdown
EXPLANATION: Lysosomes contain acidic hydrolytic enzymes that break down
macromolecules, worn-out organelles, and engulfed pathogens.
Question 3
Which organelle is responsible for modifying, sorting, and packaging proteins and lipids
for secretion?
A) Rough endoplasmic reticulum
B) Nucleolus
C) Golgi apparatus
D) Peroxisome
ANSWER: C) Golgi apparatus
, EXPLANATION: The Golgi apparatus functions like a cellular post office. It
receives proteins from the endoplasmic reticulum, modifies them, and packages
them into vesicles.
Question 4
A cell that specializes in producing large quantities of proteins for export would feature
an abundance of which organelle?
A) Smooth endoplasmic reticulum
B) Rough endoplasmic reticulum
C) Lysosomes
D) Centrioles
ANSWER: B) Rough endoplasmic reticulum
EXPLANATION: The rough endoplasmic reticulum is studded with ribosomes,
making it the primary site for synthesizing proteins destined for membranes or
secretion outside the cell.
Question 5
Which of the following structures is found in plant cells but completely absent in animal
cells?
A) Plasma membrane
B) Mitochondria
C) Cell wall
D) Ribosomes
ANSWER: C) Cell wall
EXPLANATION: Plant cells possess a rigid outer cell wall composed of cellulose
and chloroplasts for photosynthesis. Animal cells lack both.
Question 6
What is the main function of the nucleolus located inside the eukaryotic nucleus?
A) Storage of lipids
B) Synthesis of ribosomal RNA (rRNA)
C) Generation of spindle fibers
D) Breakdown of toxins
ANSWER: B) Synthesis of ribosomal RNA (rRNA)
EXPLANATION: The nucleolus is a dense region within the nucleus dedicated to
transcribing rRNA and assembling ribosomal subunits.
Question 7
Which organelle is responsible for lipid synthesis, carbohydrate metabolism, and drug
detoxification?
A) Rough endoplasmic reticulum
B) Smooth endoplasmic reticulum
C) Lysosome
D) Ribosome
ANSWER: B) Smooth endoplasmic reticulum
, EXPLANATION: Unlike the rough ER, the smooth ER lacks ribosomes and is
responsible for synthesizing lipids (like steroids) and detoxifying harmful
substances.
Question 8
Which of the following describes a key difference between prokaryotic and eukaryotic
cells?
A) Prokaryotic cells lack a plasma membrane.
B) Eukaryotic cells lack a true nucleus.
C) Prokaryotic cells lack membrane-bound organelles.
D) Eukaryotic cells lack ribosomes.
ANSWER: C) Prokaryotic cells lack membrane-bound organelles.
EXPLANATION: Prokaryotes (like bacteria) lack a nucleus and other membrane-
bound compartments, whereas eukaryotes possess them.
Question 9
What component of the cell membrane is primarily responsible for maintaining its fluid
nature across varying temperatures?
A) Peripheral proteins
B) Cholesterol
C) Glycoproteins
D) Nucleic acids
ANSWER: B) Cholesterol
EXPLANATION: Cholesterol acts as a fluidity buffer in the cell membrane,
preventing it from freezing in cold temperatures and becoming too fluid in hot
temperatures.
Question 10
Which organelle contains hydrogen peroxide and is responsible for breaking down long-
chain fatty acids?
A) Lysosome
B) Peroxisome
C) Ribosome
D) Vacuole
ANSWER: B) Peroxisome
EXPLANATION: Peroxisomes carry out oxidation reactions that break down fatty
acids and amino acids, producing hydrogen peroxide as a byproduct which they
then safely convert to water.
Question 11
What structure acts as the selective barrier regulating the movement of materials into
and out of a cell?
A) Cell wall
B) Nuclear envelope
C) Plasma membrane
D) Cytoskeleton
, ANSWER: C) Plasma membrane
EXPLANATION: The plasma membrane is a semi-permeable phospholipid bilayer
that controls what enters and exits the cytoplasm.
Question 12
Which cellular structure is made of actin filaments and provides mechanical support and
motility to the cell?
A) Microtubules
B) Microfilaments
C) Intermediate filaments
D) Extracellular matrix
ANSWER: B) Microfilaments
EXPLANATION: Microfilaments are the thinnest elements of the cytoskeleton,
composed of actin, and are crucial for cell movement and structural support.
Question 13
Which organelle uses solar energy to synthesize carbohydrates in photosynthetic
organisms?
A) Mitochondrion
B) Chloroplast
C) Chromoplast
D) Amyloplast
ANSWER: B) Chloroplast
EXPLANATION: Chloroplasts contain chlorophyll, which captures sunlight to
drive the synthesis of glucose from carbon dioxide and water during
photosynthesis.
Question 14
What is the function of the central vacuole in plant cells?
A) ATP generation
B) Protein translation
C) Storing water and maintaining turgor pressure
D) Replicating DNA
ANSWER: C) Storing water and maintaining turgor pressure
EXPLANATION: The large central vacuole stores water and solutes, exerting
turgor pressure against the cell wall to keep the plant upright.
Question 15
Which of the following structures is directly involved in organizing microtubules during
animal cell division?
A) Centrosome
B) Ribosome
C) Nucleus
D) Nucleoid
ANSWER: A) Centrosome
