PCB 3023C | PCB3023C Exam 1: Cell Biology
Updated and Latest Questions and Correct
Answers with Rationale - Florida Gulf Coast
University
1. Which of the following components of the plasma membrane is primarily responsible for
maintaining fluidity across varying temperatures?
A. Peripheral proteins
B. Nucleic acids
C. Transmembrane carbohydrates
D. Cholesterol
Correct Answer: D
Expert Explanation: Cholesterol acts as a fluidity buffer by preventing phospholipids from
packing too tightly in cold temperatures and restraining movement in heat. This molecule
intercalates between the fatty acid tails to disrupt crystalline structures. Proteins primarily
handle transport or signaling rather than structural fluidity maintenance. Carbohydrates
are typically involved in cell recognition on the exterior surface rather than fluidity.
Maintaining optimal membrane fluidity is essential for the function of integral proteins and
cellular signaling.
2. A cell is placed in a solution with a higher solute concentration than its cytosol. What is the
most likely outcome for this cell?
A. The cell will swell and potentially lyse.
B. The cell will maintain its original volume.
C. The cell will shrivel as water exits via osmosis.
D. Solutes will move into the cell via active transport.
Correct Answer: C
Expert Explanation: In a hypertonic environment, the concentration of solutes outside the
cell is greater than inside. Water naturally moves down its concentration gradient from the
cytosol to the external environment. Swelling only occurs in hypotonic solutions where the
water potential is higher outside the cell. Active transport requires energy and specific
proteins which may not be activated by simple osmotic shifts. Understanding osmotic
pressure is vital for predicting how cells respond to different physiological fluids.
3. The sodium-potassium pump (Na+/K+-ATPase) is a classic example of which transport
mechanism?
A. Simple diffusion
,B. Primary active transport
C. Facilitated diffusion
D. Secondary active transport
Correct Answer: B
Expert Explanation: The Na+/K+ pump uses ATP hydrolysis directly to move ions against
their respective concentration gradients. It pumps three sodium ions out of the cell for
every two potassium ions brought in. Simple diffusion involves movement through the
bilayer without energy or protein assistance. Facilitated diffusion uses channels or carriers
but does not require metabolic energy input. This pump is fundamental for maintaining the
resting membrane potential in animal cells.
4. Which organelle is responsible for the synthesis of lipids and the detoxification of various
poisons within the cell?
A. Rough Endoplasmic Reticulum
B. Golgi Apparatus
C. Smooth Endoplasmic Reticulum
D. Lysosome
Correct Answer: C
Expert Explanation: The Smooth ER lacks ribosomes and focuses on lipid metabolism and
detoxification processes. It is particularly abundant in liver cells where it processes drugs
and harmful metabolic byproducts. The Rough ER is primarily involved in protein synthesis
and modification due to attached ribosomes. The Golgi apparatus functions as a sorting
center for proteins but does not synthesize lipids. Detoxification is a critical survival
mechanism for cells exposed to environmental toxins.
5. During a laboratory experiment, a researcher observes a substance moving across a
membrane via a carrier protein without the use of ATP. This is known as:
A. Active transport
B. Exocytosis
C. Facilitated diffusion
D. Osmosis
Correct Answer: C
Expert Explanation: Facilitated diffusion involves the movement of polar or large
molecules across the membrane using specific transport proteins. Since the movement
follows the concentration gradient, no cellular energy in the form of ATP is required. Active
transport is incorrect because it specifically requires energy to move substances against a
, gradient. Exocytosis is a form of bulk transport using vesicles rather than individual carrier
proteins. This process allows necessary nutrients like glucose to enter cells efficiently.
6. Which of the following organelles contains its own DNA and is thought to have evolved
through endosymbiosis?
A. Mitochondrion
B. Ribosome
C. Peroxisome
D. Centriole
Correct Answer: A
Expert Explanation: Mitochondria possess circular DNA and double membranes, which
are key pieces of evidence for endosymbiotic theory. They replicate independently of the
cell’s nuclear division and produce their own proteins. Ribosomes are large complexes of
RNA and protein but lack their own genetic blueprint. Peroxisomes are involved in
oxidative reactions but do not have an independent genome. This evolutionary history
explains why mitochondria share many characteristics with modern prokaryotes.
7. What is the primary function of lysosomes in eukaryotic cells?
A. ATP production
B. Intracellular digestion
C. Photosynthesis
D. Protein folding
Correct Answer: B
Expert Explanation: Lysosomes contain hydrolytic enzymes that break down
macromolecules, damaged organelles, and foreign substances. They maintain an acidic
internal pH to ensure these enzymes function effectively without damaging the rest of the
cell. ATP production is the primary role of the mitochondria, not the lysosome.
Photosynthesis occurs in chloroplasts, which are absent in animal cells where lysosomes
are most prominent. Waste management is essential for cellular health and the recycling of
molecular building blocks.
8. Which type of signaling involves a cell secreting a signaling molecule that acts on nearby
target cells?
A. Endocrine signaling
B. Autocrine signaling
C. Paracrine signaling
D. Synaptic signaling
Updated and Latest Questions and Correct
Answers with Rationale - Florida Gulf Coast
University
1. Which of the following components of the plasma membrane is primarily responsible for
maintaining fluidity across varying temperatures?
A. Peripheral proteins
B. Nucleic acids
C. Transmembrane carbohydrates
D. Cholesterol
Correct Answer: D
Expert Explanation: Cholesterol acts as a fluidity buffer by preventing phospholipids from
packing too tightly in cold temperatures and restraining movement in heat. This molecule
intercalates between the fatty acid tails to disrupt crystalline structures. Proteins primarily
handle transport or signaling rather than structural fluidity maintenance. Carbohydrates
are typically involved in cell recognition on the exterior surface rather than fluidity.
Maintaining optimal membrane fluidity is essential for the function of integral proteins and
cellular signaling.
2. A cell is placed in a solution with a higher solute concentration than its cytosol. What is the
most likely outcome for this cell?
A. The cell will swell and potentially lyse.
B. The cell will maintain its original volume.
C. The cell will shrivel as water exits via osmosis.
D. Solutes will move into the cell via active transport.
Correct Answer: C
Expert Explanation: In a hypertonic environment, the concentration of solutes outside the
cell is greater than inside. Water naturally moves down its concentration gradient from the
cytosol to the external environment. Swelling only occurs in hypotonic solutions where the
water potential is higher outside the cell. Active transport requires energy and specific
proteins which may not be activated by simple osmotic shifts. Understanding osmotic
pressure is vital for predicting how cells respond to different physiological fluids.
3. The sodium-potassium pump (Na+/K+-ATPase) is a classic example of which transport
mechanism?
A. Simple diffusion
,B. Primary active transport
C. Facilitated diffusion
D. Secondary active transport
Correct Answer: B
Expert Explanation: The Na+/K+ pump uses ATP hydrolysis directly to move ions against
their respective concentration gradients. It pumps three sodium ions out of the cell for
every two potassium ions brought in. Simple diffusion involves movement through the
bilayer without energy or protein assistance. Facilitated diffusion uses channels or carriers
but does not require metabolic energy input. This pump is fundamental for maintaining the
resting membrane potential in animal cells.
4. Which organelle is responsible for the synthesis of lipids and the detoxification of various
poisons within the cell?
A. Rough Endoplasmic Reticulum
B. Golgi Apparatus
C. Smooth Endoplasmic Reticulum
D. Lysosome
Correct Answer: C
Expert Explanation: The Smooth ER lacks ribosomes and focuses on lipid metabolism and
detoxification processes. It is particularly abundant in liver cells where it processes drugs
and harmful metabolic byproducts. The Rough ER is primarily involved in protein synthesis
and modification due to attached ribosomes. The Golgi apparatus functions as a sorting
center for proteins but does not synthesize lipids. Detoxification is a critical survival
mechanism for cells exposed to environmental toxins.
5. During a laboratory experiment, a researcher observes a substance moving across a
membrane via a carrier protein without the use of ATP. This is known as:
A. Active transport
B. Exocytosis
C. Facilitated diffusion
D. Osmosis
Correct Answer: C
Expert Explanation: Facilitated diffusion involves the movement of polar or large
molecules across the membrane using specific transport proteins. Since the movement
follows the concentration gradient, no cellular energy in the form of ATP is required. Active
transport is incorrect because it specifically requires energy to move substances against a
, gradient. Exocytosis is a form of bulk transport using vesicles rather than individual carrier
proteins. This process allows necessary nutrients like glucose to enter cells efficiently.
6. Which of the following organelles contains its own DNA and is thought to have evolved
through endosymbiosis?
A. Mitochondrion
B. Ribosome
C. Peroxisome
D. Centriole
Correct Answer: A
Expert Explanation: Mitochondria possess circular DNA and double membranes, which
are key pieces of evidence for endosymbiotic theory. They replicate independently of the
cell’s nuclear division and produce their own proteins. Ribosomes are large complexes of
RNA and protein but lack their own genetic blueprint. Peroxisomes are involved in
oxidative reactions but do not have an independent genome. This evolutionary history
explains why mitochondria share many characteristics with modern prokaryotes.
7. What is the primary function of lysosomes in eukaryotic cells?
A. ATP production
B. Intracellular digestion
C. Photosynthesis
D. Protein folding
Correct Answer: B
Expert Explanation: Lysosomes contain hydrolytic enzymes that break down
macromolecules, damaged organelles, and foreign substances. They maintain an acidic
internal pH to ensure these enzymes function effectively without damaging the rest of the
cell. ATP production is the primary role of the mitochondria, not the lysosome.
Photosynthesis occurs in chloroplasts, which are absent in animal cells where lysosomes
are most prominent. Waste management is essential for cellular health and the recycling of
molecular building blocks.
8. Which type of signaling involves a cell secreting a signaling molecule that acts on nearby
target cells?
A. Endocrine signaling
B. Autocrine signaling
C. Paracrine signaling
D. Synaptic signaling
