HESI A2 V2 BIOLOGY TEST BANK 260
PRACTICE QUESTIONS WITH ANSWERS &
RATIONALES
EXAM SUCCESS TIPS FOR HESI A2 BIOLOGY:
Focus on understanding concepts, not just memorizing facts — HESI questions test
application
Know the differences between mitosis and meiosis thoroughly
Master the central dogma: DNA → RNA → Protein
Understand the relationship between structure and function at the cellular level
Review the major metabolic pathways: photosynthesis and cellular respiration
Know your Mendelian genetics ratios and be able to set up Punnett squares quickly
Review ecological relationships and levels of organization
Remember: HESI A2 tests critical thinking — always ask "why" and "how" when
studying
CELL BIOLOGY & CELL STRUCTURE
1. Which organelle is responsible for producing energy (ATP) in eukaryotic cells?
A) Ribosome B) Golgi apparatus C) Mitochondria D) Lysosome
C) Mitochondria (correct answer)
RATIONALE: The mitochondria are known as the "powerhouse of the cell" because they
carry out cellular respiration, converting glucose and oxygen into ATP (adenosine
triphosphate), which is the cell's primary energy currency. Mitochondria have their own
DNA and double membrane, with the inner membrane folded into cristae that increase
surface area for ATP production.
2. Which of the following best describes the function of the cell membrane?
A) It stores genetic information for the cell B) It produces proteins for export out of the cell C) It
regulates what enters and exits the cell D) It provides rigid structural support to the cell
,C) It regulates what enters and exits the cell (correct answer)
RATIONALE: The cell membrane (plasma membrane) is selectively permeable, meaning it
controls the movement of substances into and out of the cell. It is composed of a
phospholipid bilayer embedded with proteins, cholesterol, and carbohydrates. This
structure allows the membrane to regulate ion concentrations, nutrient uptake, waste
removal, and cell communication.
3. Which organelle is known as the "post office" of the cell because it packages and ships
proteins?
A) Endoplasmic reticulum B) Mitochondria C) Golgi apparatus D) Nucleus
C) Golgi apparatus (correct answer)
RATIONALE: The Golgi apparatus receives proteins from the rough endoplasmic
reticulum, modifies them (adds carbohydrate chains, sorts them), packages them into
vesicles, and ships them to their destination — either to the cell membrane for secretion or
to other organelles. It functions like a post office, processing and directing cellular
products.
4. Which structure is found in plant cells but NOT in animal cells?
A) Mitochondria B) Cell wall and chloroplasts C) Ribosome D) Golgi apparatus
B) Cell wall and chloroplasts (correct answer)
RATIONALE: Plant cells have a rigid cell wall made of cellulose that provides structural
support, and chloroplasts that contain chlorophyll for photosynthesis. Animal cells lack
both structures. Plant cells also have a large central vacuole for storage and turgor
pressure. Both plant and animal cells contain mitochondria, ribosomes, and Golgi
apparatus.
5. The nucleus of a cell contains:
A) Ribosomes and ATP B) DNA and the nucleolus C) Cristae and matrix D) Thylakoids and
grana
B) DNA and the nucleolus (correct answer)
,RATIONALE: The nucleus is the control center of the cell and contains the cell's genetic
material (DNA organized into chromosomes) and the nucleolus, which is responsible for
producing ribosomal RNA (rRNA) and assembling ribosome subunits. The nucleus is
surrounded by a double nuclear envelope with pores that regulate the passage of molecules
between the nucleus and cytoplasm.
6. Ribosomes are responsible for:
A) Lipid synthesis B) ATP production C) Protein synthesis D) DNA replication
C) Protein synthesis (correct answer)
RATIONALE: Ribosomes are the cellular machinery responsible for translating messenger
RNA (mRNA) into proteins. They can be found free in the cytoplasm (producing proteins
for use within the cell) or attached to the rough endoplasmic reticulum (producing proteins
destined for secretion or insertion into membranes). Ribosomes are composed of ribosomal
RNA (rRNA) and proteins.
7. The smooth endoplasmic reticulum (SER) is primarily responsible for:
A) Protein synthesis B) Lipid synthesis and detoxification C) DNA transcription D) Packaging
proteins into vesicles
B) Lipid synthesis and detoxification (correct answer)
RATIONALE: The smooth endoplasmic reticulum lacks ribosomes (hence "smooth") and
is responsible for lipid and steroid hormone synthesis, metabolism of carbohydrates, and
detoxification of drugs and poisons (particularly in liver cells). The rough ER, by contrast,
is studded with ribosomes and is involved in protein synthesis and modification.
8. Which of the following is a characteristic of prokaryotic cells?
A) Membrane-bound nucleus and organelles B) No membrane-bound nucleus; circular DNA in
the cytoplasm C) Presence of mitochondria and chloroplasts D) Large size compared to
eukaryotic cells
B) No membrane-bound nucleus; circular DNA in the cytoplasm (correct answer)
RATIONALE: Prokaryotic cells (bacteria and archaea) lack a membrane-bound nucleus.
Their DNA is circular and located in the nucleoid region of the cytoplasm. They also lack
, membrane-bound organelles. Prokaryotes are generally much smaller than eukaryotic
cells. They do have ribosomes (70S), a cell membrane, and often a cell wall, but these are
structurally different from eukaryotic counterparts.
9. Lysosomes function primarily to:
A) Synthesize lipids for the cell membrane B) Digest waste materials, cellular debris, and foreign
invaders C) Produce energy through cellular respiration D) Transport proteins to the Golgi
apparatus
B) Digest waste materials, cellular debris, and foreign invaders (correct answer)
RATIONALE: Lysosomes are membrane-bound organelles that contain hydrolytic
(digestive) enzymes capable of breaking down proteins, lipids, carbohydrates, and nucleic
acids. They function in autophagy (digesting damaged organelles), phagocytosis (digesting
engulfed pathogens), and apoptosis (programmed cell death). Without lysosomes, cellular
waste and debris would accumulate, leading to disease (e.g., Tay-Sachs disease).
10. Which type of microscopy is BEST suited for viewing the internal ultrastructure of a
cell?
A) Light microscopy B) Phase-contrast microscopy C) Transmission electron microscopy (TEM)
D) Fluorescence microscopy
C) Transmission electron microscopy (TEM) (correct answer)
RATIONALE: Transmission electron microscopy uses a beam of electrons rather than
light, allowing resolution of structures at the nanometer level. This makes TEM the best
tool for viewing the internal ultrastructure of cells — including individual organelle
membranes, ribosomes, and cytoskeletal filaments. Light microscopy has limited resolution
(~ 200 nm) and cannot resolve subcellular structures in such fine detail.
CELL TRANSPORT
11. Which process moves substances from an area of HIGH concentration to an area of
LOW concentration without using energy?
A) Active transport B) Endocytosis C) Passive diffusion D) Phagocytosis
PRACTICE QUESTIONS WITH ANSWERS &
RATIONALES
EXAM SUCCESS TIPS FOR HESI A2 BIOLOGY:
Focus on understanding concepts, not just memorizing facts — HESI questions test
application
Know the differences between mitosis and meiosis thoroughly
Master the central dogma: DNA → RNA → Protein
Understand the relationship between structure and function at the cellular level
Review the major metabolic pathways: photosynthesis and cellular respiration
Know your Mendelian genetics ratios and be able to set up Punnett squares quickly
Review ecological relationships and levels of organization
Remember: HESI A2 tests critical thinking — always ask "why" and "how" when
studying
CELL BIOLOGY & CELL STRUCTURE
1. Which organelle is responsible for producing energy (ATP) in eukaryotic cells?
A) Ribosome B) Golgi apparatus C) Mitochondria D) Lysosome
C) Mitochondria (correct answer)
RATIONALE: The mitochondria are known as the "powerhouse of the cell" because they
carry out cellular respiration, converting glucose and oxygen into ATP (adenosine
triphosphate), which is the cell's primary energy currency. Mitochondria have their own
DNA and double membrane, with the inner membrane folded into cristae that increase
surface area for ATP production.
2. Which of the following best describes the function of the cell membrane?
A) It stores genetic information for the cell B) It produces proteins for export out of the cell C) It
regulates what enters and exits the cell D) It provides rigid structural support to the cell
,C) It regulates what enters and exits the cell (correct answer)
RATIONALE: The cell membrane (plasma membrane) is selectively permeable, meaning it
controls the movement of substances into and out of the cell. It is composed of a
phospholipid bilayer embedded with proteins, cholesterol, and carbohydrates. This
structure allows the membrane to regulate ion concentrations, nutrient uptake, waste
removal, and cell communication.
3. Which organelle is known as the "post office" of the cell because it packages and ships
proteins?
A) Endoplasmic reticulum B) Mitochondria C) Golgi apparatus D) Nucleus
C) Golgi apparatus (correct answer)
RATIONALE: The Golgi apparatus receives proteins from the rough endoplasmic
reticulum, modifies them (adds carbohydrate chains, sorts them), packages them into
vesicles, and ships them to their destination — either to the cell membrane for secretion or
to other organelles. It functions like a post office, processing and directing cellular
products.
4. Which structure is found in plant cells but NOT in animal cells?
A) Mitochondria B) Cell wall and chloroplasts C) Ribosome D) Golgi apparatus
B) Cell wall and chloroplasts (correct answer)
RATIONALE: Plant cells have a rigid cell wall made of cellulose that provides structural
support, and chloroplasts that contain chlorophyll for photosynthesis. Animal cells lack
both structures. Plant cells also have a large central vacuole for storage and turgor
pressure. Both plant and animal cells contain mitochondria, ribosomes, and Golgi
apparatus.
5. The nucleus of a cell contains:
A) Ribosomes and ATP B) DNA and the nucleolus C) Cristae and matrix D) Thylakoids and
grana
B) DNA and the nucleolus (correct answer)
,RATIONALE: The nucleus is the control center of the cell and contains the cell's genetic
material (DNA organized into chromosomes) and the nucleolus, which is responsible for
producing ribosomal RNA (rRNA) and assembling ribosome subunits. The nucleus is
surrounded by a double nuclear envelope with pores that regulate the passage of molecules
between the nucleus and cytoplasm.
6. Ribosomes are responsible for:
A) Lipid synthesis B) ATP production C) Protein synthesis D) DNA replication
C) Protein synthesis (correct answer)
RATIONALE: Ribosomes are the cellular machinery responsible for translating messenger
RNA (mRNA) into proteins. They can be found free in the cytoplasm (producing proteins
for use within the cell) or attached to the rough endoplasmic reticulum (producing proteins
destined for secretion or insertion into membranes). Ribosomes are composed of ribosomal
RNA (rRNA) and proteins.
7. The smooth endoplasmic reticulum (SER) is primarily responsible for:
A) Protein synthesis B) Lipid synthesis and detoxification C) DNA transcription D) Packaging
proteins into vesicles
B) Lipid synthesis and detoxification (correct answer)
RATIONALE: The smooth endoplasmic reticulum lacks ribosomes (hence "smooth") and
is responsible for lipid and steroid hormone synthesis, metabolism of carbohydrates, and
detoxification of drugs and poisons (particularly in liver cells). The rough ER, by contrast,
is studded with ribosomes and is involved in protein synthesis and modification.
8. Which of the following is a characteristic of prokaryotic cells?
A) Membrane-bound nucleus and organelles B) No membrane-bound nucleus; circular DNA in
the cytoplasm C) Presence of mitochondria and chloroplasts D) Large size compared to
eukaryotic cells
B) No membrane-bound nucleus; circular DNA in the cytoplasm (correct answer)
RATIONALE: Prokaryotic cells (bacteria and archaea) lack a membrane-bound nucleus.
Their DNA is circular and located in the nucleoid region of the cytoplasm. They also lack
, membrane-bound organelles. Prokaryotes are generally much smaller than eukaryotic
cells. They do have ribosomes (70S), a cell membrane, and often a cell wall, but these are
structurally different from eukaryotic counterparts.
9. Lysosomes function primarily to:
A) Synthesize lipids for the cell membrane B) Digest waste materials, cellular debris, and foreign
invaders C) Produce energy through cellular respiration D) Transport proteins to the Golgi
apparatus
B) Digest waste materials, cellular debris, and foreign invaders (correct answer)
RATIONALE: Lysosomes are membrane-bound organelles that contain hydrolytic
(digestive) enzymes capable of breaking down proteins, lipids, carbohydrates, and nucleic
acids. They function in autophagy (digesting damaged organelles), phagocytosis (digesting
engulfed pathogens), and apoptosis (programmed cell death). Without lysosomes, cellular
waste and debris would accumulate, leading to disease (e.g., Tay-Sachs disease).
10. Which type of microscopy is BEST suited for viewing the internal ultrastructure of a
cell?
A) Light microscopy B) Phase-contrast microscopy C) Transmission electron microscopy (TEM)
D) Fluorescence microscopy
C) Transmission electron microscopy (TEM) (correct answer)
RATIONALE: Transmission electron microscopy uses a beam of electrons rather than
light, allowing resolution of structures at the nanometer level. This makes TEM the best
tool for viewing the internal ultrastructure of cells — including individual organelle
membranes, ribosomes, and cytoskeletal filaments. Light microscopy has limited resolution
(~ 200 nm) and cannot resolve subcellular structures in such fine detail.
CELL TRANSPORT
11. Which process moves substances from an area of HIGH concentration to an area of
LOW concentration without using energy?
A) Active transport B) Endocytosis C) Passive diffusion D) Phagocytosis
