HESI A2 BIOLOGY EXAM ACTUAL QUESTIONS
AND ANSWERS
Cell Biology & Organelles
1. Which organelle is responsible for protein synthesis?
• A. Mitochondrion
• B. Vacuole
• C. Cell membrane
• D. Ribosome ✅
Rationale: Ribosomes, either free in the cytoplasm or bound to the rough endoplasmic
reticulum, assemble proteins by translating mRNA into polypeptide chains.
Mitochondria produce energy, vacuoles store materials, and the cell membrane
regulates transport .
2. Which organelle would you expect to be present in a cell responsible for
detoxifying multiple molecules?
• A. Rough ER
• B. Smooth ER ✅
• C. Lysosome
• D. Golgi apparatus
Rationale: The smooth endoplasmic reticulum (SER) is responsible for detoxifying drugs
and toxins, particularly in liver cells. The rough ER is involved in protein synthesis,
lysosomes digest waste, and the Golgi apparatus processes proteins .
,3. A cell from heart muscle would more than likely contain an unusually high
proportion of:
• A. Lysosomes
• B. Mitochondria ✅
• C. mRNA
• D. Ribosomes
Rationale: Heart muscle cells require significant energy for continuous contraction, so
they contain abundant mitochondria for ATP production through cellular respiration .
4. The nucleus is important in a cell because:
• A. It stores the DNA ✅
• B. It supports the cell
• C. It makes protein
• D. It makes energy out of food
Rationale: The nucleus is the "brain" of the cell and stores genetic material (DNA). The
cell wall provides support (in plants), ribosomes make protein, and mitochondria
produce energy.
5. How is the plasma membrane arranged?
• A. In a single layer made of proteins
• B. In a double layer made of proteins
• C. In a single layer of phospholipids
• D. In a double layer of phospholipids ✅
,Rationale: The plasma membrane consists of a phospholipid bilayer with two layers of
phospholipids. The hydrophilic phosphate heads face outward, and the hydrophobic
fatty acid tails face inward .
6. Which organelle is associated with hydrolytic enzymes and is sometimes
referred to as a "suicide bag"?
• A. Ribosome
• B. Mitochondrion
• C. Lysosome ✅
• D. Golgi apparatus
Rationale: Lysosomes contain digestive enzymes that break down waste materials and
cellular debris. They are called "suicide bags" because they can digest the cell itself if
ruptured .
7. Which organelle is responsible for packaging, processing, and shipping
proteins?
• A. Ribosome
• B. Smooth ER
• C. Golgi apparatus ✅
• D. Nucleus
Rationale: The Golgi apparatus modifies, sorts, and packages proteins for secretion or
delivery to other organelles. Ribosomes synthesize proteins, the SER detoxifies, and the
nucleus stores DNA .
, 8. What is the basic unit of life?
• A. Atom
• B. Molecule
• C. Cell ✅
• D. Tissue
Rationale: The cell is the smallest unit capable of performing all life functions. Atoms
and molecules are components of cells, and tissues are groups of cells .
9. Which structure controls what enters and exits a cell?
• A. Nucleus
• B. Cell membrane ✅
• C. Cytoplasm
• D. Mitochondrion
Rationale: The cell membrane, a selectively permeable barrier, regulates the movement
of substances in and out of the cell. The nucleus stores DNA, cytoplasm is the fluid
inside cells, and mitochondria produce energy .
10. What primarily determines the shape of cells that lack cell walls?
• A. Nucleus
• B. Cell membrane
• C. Cytoplasm
AND ANSWERS
Cell Biology & Organelles
1. Which organelle is responsible for protein synthesis?
• A. Mitochondrion
• B. Vacuole
• C. Cell membrane
• D. Ribosome ✅
Rationale: Ribosomes, either free in the cytoplasm or bound to the rough endoplasmic
reticulum, assemble proteins by translating mRNA into polypeptide chains.
Mitochondria produce energy, vacuoles store materials, and the cell membrane
regulates transport .
2. Which organelle would you expect to be present in a cell responsible for
detoxifying multiple molecules?
• A. Rough ER
• B. Smooth ER ✅
• C. Lysosome
• D. Golgi apparatus
Rationale: The smooth endoplasmic reticulum (SER) is responsible for detoxifying drugs
and toxins, particularly in liver cells. The rough ER is involved in protein synthesis,
lysosomes digest waste, and the Golgi apparatus processes proteins .
,3. A cell from heart muscle would more than likely contain an unusually high
proportion of:
• A. Lysosomes
• B. Mitochondria ✅
• C. mRNA
• D. Ribosomes
Rationale: Heart muscle cells require significant energy for continuous contraction, so
they contain abundant mitochondria for ATP production through cellular respiration .
4. The nucleus is important in a cell because:
• A. It stores the DNA ✅
• B. It supports the cell
• C. It makes protein
• D. It makes energy out of food
Rationale: The nucleus is the "brain" of the cell and stores genetic material (DNA). The
cell wall provides support (in plants), ribosomes make protein, and mitochondria
produce energy.
5. How is the plasma membrane arranged?
• A. In a single layer made of proteins
• B. In a double layer made of proteins
• C. In a single layer of phospholipids
• D. In a double layer of phospholipids ✅
,Rationale: The plasma membrane consists of a phospholipid bilayer with two layers of
phospholipids. The hydrophilic phosphate heads face outward, and the hydrophobic
fatty acid tails face inward .
6. Which organelle is associated with hydrolytic enzymes and is sometimes
referred to as a "suicide bag"?
• A. Ribosome
• B. Mitochondrion
• C. Lysosome ✅
• D. Golgi apparatus
Rationale: Lysosomes contain digestive enzymes that break down waste materials and
cellular debris. They are called "suicide bags" because they can digest the cell itself if
ruptured .
7. Which organelle is responsible for packaging, processing, and shipping
proteins?
• A. Ribosome
• B. Smooth ER
• C. Golgi apparatus ✅
• D. Nucleus
Rationale: The Golgi apparatus modifies, sorts, and packages proteins for secretion or
delivery to other organelles. Ribosomes synthesize proteins, the SER detoxifies, and the
nucleus stores DNA .
, 8. What is the basic unit of life?
• A. Atom
• B. Molecule
• C. Cell ✅
• D. Tissue
Rationale: The cell is the smallest unit capable of performing all life functions. Atoms
and molecules are components of cells, and tissues are groups of cells .
9. Which structure controls what enters and exits a cell?
• A. Nucleus
• B. Cell membrane ✅
• C. Cytoplasm
• D. Mitochondrion
Rationale: The cell membrane, a selectively permeable barrier, regulates the movement
of substances in and out of the cell. The nucleus stores DNA, cytoplasm is the fluid
inside cells, and mitochondria produce energy .
10. What primarily determines the shape of cells that lack cell walls?
• A. Nucleus
• B. Cell membrane
• C. Cytoplasm
