HESI A2 Biology 2024/2025 – 100% Verified Answers with
Expert Explanations
Cell Biology
Question 1: Which organelle is primarily responsible for energy production in eukaryotic cells?
a) Nucleus
b) Mitochondrion
c) Golgi apparatus
d) Endoplasmic reticulum
Answer: b) Mitochondrion
Explanation: Mitochondria are known as the powerhouses of the cell because they pro-
duce ATP through cellular respiration, specifically via the process of oxidative phospho-
rylation in the inner mitochondrial membrane.
Question 2: What is the primary function of the cell membrane?
a) Synthesize proteins
b) Regulate transport of substances
c) Store genetic material
d) Produce energy
Answer: b) Regulate transport of substances
Explanation: The cell membrane, a lipid bilayer, controls the movement of substances
in and out of the cell, maintaining homeostasis through selective permeability.
Question 3: Which process allows cells to engulf large particles, such as bacteria?
a) Diffusion
b) Osmosis
c) Phagocytosis
d) Active transport
Answer: c) Phagocytosis
Explanation: Phagocytosis is a form of endocytosis where cells, such as macrophages,
engulf large particles by extending their pseudopodia and forming a phagosome.
Question 4: What is the role of ribosomes in the cell?
a) Lipid synthesis
b) Protein synthesis
c) DNA replication
d) Energy storage
Answer: b) Protein synthesis
Explanation: Ribosomes, found free in the cytoplasm or bound to the endoplasmic retic-
ulum, are the sites where amino acids are assembled into proteins based on mRNA in-
structions.
Question 5: Which structure in plant cells is responsible for photosynthesis?
a) Chloroplast
b) Vacuole
c) Cell wall
d) Nucleus
Answer: a) Chloroplast
1
, Explanation: Chloroplasts contain chlorophyll, which captures light energy to drive pho-
tosynthesis, converting carbon dioxide and water into glucose and oxygen.
Question 6: What is the primary component of the cell wall in plant cells?
a) Chitin
b) Cellulose
c) Peptidoglycan
d) Phospholipids
Answer: b) Cellulose
Explanation: Cellulose, a polysaccharide, forms the rigid structure of plant cell walls,
providing support and protection.
Question 7: Which type of cell lacks a nucleus?
a) Eukaryotic
b) Prokaryotic
c) Animal
d) Plant
Answer: b) Prokaryotic
Explanation: Prokaryotic cells, such as bacteria, lack a true nucleus; their genetic mate-
rial is located in a nucleoid region without a membrane.
Question 8: What is the function of the lysosome in a cell?
a) Protein modification
b) Waste digestion
c) Energy production
d) Cell division
Answer: b) Waste digestion
Explanation: Lysosomes contain hydrolytic enzymes that break down waste materials,
damaged organelles, and engulfed pathogens within the cell.
Question 9: Which molecule provides the energy for active transport across the cell membrane?
a) Glucose
b) ATP
c) DNA
d) RNA
Answer: b) ATP
Explanation: Active transport requires energy, typically in the form of ATP, to move
molecules against their concentration gradient, as seen in the sodium-potassium pump.
Question 10: What is the term for the movement of water across a semipermeable membrane?
a) Diffusion
b) Osmosis
c) Facilitated diffusion
d) Active transport
Answer: b) Osmosis
Explanation: Osmosis is the passive movement of water molecules across a semiper-
meable membrane from an area of lower solute concentration to an area of higher solute
concentration.
Question 11: Which organelle modifies and packages proteins for secretion?
a) Mitochondrion
2
Expert Explanations
Cell Biology
Question 1: Which organelle is primarily responsible for energy production in eukaryotic cells?
a) Nucleus
b) Mitochondrion
c) Golgi apparatus
d) Endoplasmic reticulum
Answer: b) Mitochondrion
Explanation: Mitochondria are known as the powerhouses of the cell because they pro-
duce ATP through cellular respiration, specifically via the process of oxidative phospho-
rylation in the inner mitochondrial membrane.
Question 2: What is the primary function of the cell membrane?
a) Synthesize proteins
b) Regulate transport of substances
c) Store genetic material
d) Produce energy
Answer: b) Regulate transport of substances
Explanation: The cell membrane, a lipid bilayer, controls the movement of substances
in and out of the cell, maintaining homeostasis through selective permeability.
Question 3: Which process allows cells to engulf large particles, such as bacteria?
a) Diffusion
b) Osmosis
c) Phagocytosis
d) Active transport
Answer: c) Phagocytosis
Explanation: Phagocytosis is a form of endocytosis where cells, such as macrophages,
engulf large particles by extending their pseudopodia and forming a phagosome.
Question 4: What is the role of ribosomes in the cell?
a) Lipid synthesis
b) Protein synthesis
c) DNA replication
d) Energy storage
Answer: b) Protein synthesis
Explanation: Ribosomes, found free in the cytoplasm or bound to the endoplasmic retic-
ulum, are the sites where amino acids are assembled into proteins based on mRNA in-
structions.
Question 5: Which structure in plant cells is responsible for photosynthesis?
a) Chloroplast
b) Vacuole
c) Cell wall
d) Nucleus
Answer: a) Chloroplast
1
, Explanation: Chloroplasts contain chlorophyll, which captures light energy to drive pho-
tosynthesis, converting carbon dioxide and water into glucose and oxygen.
Question 6: What is the primary component of the cell wall in plant cells?
a) Chitin
b) Cellulose
c) Peptidoglycan
d) Phospholipids
Answer: b) Cellulose
Explanation: Cellulose, a polysaccharide, forms the rigid structure of plant cell walls,
providing support and protection.
Question 7: Which type of cell lacks a nucleus?
a) Eukaryotic
b) Prokaryotic
c) Animal
d) Plant
Answer: b) Prokaryotic
Explanation: Prokaryotic cells, such as bacteria, lack a true nucleus; their genetic mate-
rial is located in a nucleoid region without a membrane.
Question 8: What is the function of the lysosome in a cell?
a) Protein modification
b) Waste digestion
c) Energy production
d) Cell division
Answer: b) Waste digestion
Explanation: Lysosomes contain hydrolytic enzymes that break down waste materials,
damaged organelles, and engulfed pathogens within the cell.
Question 9: Which molecule provides the energy for active transport across the cell membrane?
a) Glucose
b) ATP
c) DNA
d) RNA
Answer: b) ATP
Explanation: Active transport requires energy, typically in the form of ATP, to move
molecules against their concentration gradient, as seen in the sodium-potassium pump.
Question 10: What is the term for the movement of water across a semipermeable membrane?
a) Diffusion
b) Osmosis
c) Facilitated diffusion
d) Active transport
Answer: b) Osmosis
Explanation: Osmosis is the passive movement of water molecules across a semiper-
meable membrane from an area of lower solute concentration to an area of higher solute
concentration.
Question 11: Which organelle modifies and packages proteins for secretion?
a) Mitochondrion
2
