PCB3023C Cell Biology Exam 2 Review 2026 – FGCU
1. Which component of the plasma membrane is primarily responsible for
forming the basic structure and acts as a barrier to most water-soluble
substances?
A. Peripheral proteins
B. Phospholipid bilayer
C. Glycoproteins
D. Cholesterol
Answer: B
Rationale: The phospholipid bilayer forms the fundamental structure of the cell
membrane, with hydrophobic tails pointing inward to create a barrier.
2. In the fluid mosaic model, what does the term ‘mosaic’ refer to?
A. The fluid nature of the lipids
B. The various proteins embedded in or attached to the bilayer
C. The movement of water across the membrane
D. The constant change in membrane thickness
Answer: B
Rationale: ‘Mosaic’ refers to the diverse arrangement of proteins dispersed throughout the
lipid bilayer.
,3. Which factor would most likely increase the fluidity of a cell membrane?
A. An increase in saturated fatty acid chains
B. An increase in phospholipids with unsaturated fatty acid tails
C. A decrease in temperature
D. An increase in long-chain fatty acids
Answer: B
Rationale: Unsaturated fatty acids have ‘kinks’ due to double bonds, which prevent tight
packing and increase fluidity.
4. What is the role of cholesterol in animal cell membranes at high
temperatures?
A. It increases fluidity by disrupting packing
B. It promotes the breakdown of phospholipids
C. It stabilizes the membrane and reduces fluidity
D. It acts as a transport channel for ions
Answer: C
Rationale: At high temperatures, cholesterol restricts the movement of phospholipids,
thereby reducing fluidity and stabilizing the membrane.
5. Which type of membrane protein spans the entire lipid bilayer?
A. Peripheral protein
B. Lipid-anchored protein
C. Integral (transmembrane) protein
D. Extrinsic protein
Answer: C
Rationale: Integral or transmembrane proteins have hydrophobic regions that span the
interior of the lipid bilayer.
, 6. Which of the following molecules can most easily diffuse through the lipid
bilayer without the help of a transport protein?
A. Glucose
B. Sodium ions (Na+)
C. Oxygen (O2)
D. Amino acids
Answer: C
Rationale: Small, nonpolar molecules like O2 and CO2 can pass directly through the
hydrophobic core of the membrane.
7. What defines ‘facilitated diffusion’?
A. Movement of solutes down a gradient via a specific carrier or channel
B. Movement of solutes against a gradient using ATP
C. Direct movement of water through the bilayer
D. Engulfing of large particles by the membrane
Answer: A
Rationale: Facilitated diffusion is a passive process that uses membrane proteins to move
polar or charged substances down their concentration gradient.
8. The sodium-potassium pump (Na+/K+ ATPase) is an example of:
A. Primary active transport
B. Facilitated diffusion
C. Simple diffusion
D. Secondary active transport
Answer: A
Rationale: It uses ATP directly to pump Na+ out and K+ in against their respective
concentration gradients.
1. Which component of the plasma membrane is primarily responsible for
forming the basic structure and acts as a barrier to most water-soluble
substances?
A. Peripheral proteins
B. Phospholipid bilayer
C. Glycoproteins
D. Cholesterol
Answer: B
Rationale: The phospholipid bilayer forms the fundamental structure of the cell
membrane, with hydrophobic tails pointing inward to create a barrier.
2. In the fluid mosaic model, what does the term ‘mosaic’ refer to?
A. The fluid nature of the lipids
B. The various proteins embedded in or attached to the bilayer
C. The movement of water across the membrane
D. The constant change in membrane thickness
Answer: B
Rationale: ‘Mosaic’ refers to the diverse arrangement of proteins dispersed throughout the
lipid bilayer.
,3. Which factor would most likely increase the fluidity of a cell membrane?
A. An increase in saturated fatty acid chains
B. An increase in phospholipids with unsaturated fatty acid tails
C. A decrease in temperature
D. An increase in long-chain fatty acids
Answer: B
Rationale: Unsaturated fatty acids have ‘kinks’ due to double bonds, which prevent tight
packing and increase fluidity.
4. What is the role of cholesterol in animal cell membranes at high
temperatures?
A. It increases fluidity by disrupting packing
B. It promotes the breakdown of phospholipids
C. It stabilizes the membrane and reduces fluidity
D. It acts as a transport channel for ions
Answer: C
Rationale: At high temperatures, cholesterol restricts the movement of phospholipids,
thereby reducing fluidity and stabilizing the membrane.
5. Which type of membrane protein spans the entire lipid bilayer?
A. Peripheral protein
B. Lipid-anchored protein
C. Integral (transmembrane) protein
D. Extrinsic protein
Answer: C
Rationale: Integral or transmembrane proteins have hydrophobic regions that span the
interior of the lipid bilayer.
, 6. Which of the following molecules can most easily diffuse through the lipid
bilayer without the help of a transport protein?
A. Glucose
B. Sodium ions (Na+)
C. Oxygen (O2)
D. Amino acids
Answer: C
Rationale: Small, nonpolar molecules like O2 and CO2 can pass directly through the
hydrophobic core of the membrane.
7. What defines ‘facilitated diffusion’?
A. Movement of solutes down a gradient via a specific carrier or channel
B. Movement of solutes against a gradient using ATP
C. Direct movement of water through the bilayer
D. Engulfing of large particles by the membrane
Answer: A
Rationale: Facilitated diffusion is a passive process that uses membrane proteins to move
polar or charged substances down their concentration gradient.
8. The sodium-potassium pump (Na+/K+ ATPase) is an example of:
A. Primary active transport
B. Facilitated diffusion
C. Simple diffusion
D. Secondary active transport
Answer: A
Rationale: It uses ATP directly to pump Na+ out and K+ in against their respective
concentration gradients.
