PCB 3023C Exam 2: Cell Biology Questions & Answers | Grade A |
100% Correct - Florida Gulf Coast University
1. Which of the following factors would most likely increase the fluidity of a lipid
bilayer?
A. A higher concentration of saturated fatty acid tails
B. Decreased temperature
C. Longer fatty acid chain lengths
D. A higher concentration of unsaturated fatty acid tails
E. None of the above
Answer: D
Explanation: Unsaturated fatty acid tails have kinks that prevent tight packing, thereby
increasing membrane fluidity, especially at lower temperatures.
2. What is the primary role of cholesterol in animal cell membranes at high
temperatures?
A. To increase fluidity by creating gaps
B. To make the membrane more permeable to ions
C. To stabilize the membrane and decrease fluidity
D. To synthesize ATP
Answer: C
Explanation: Cholesterol acts as a fluidity buffer; at high temperatures, it restricts the
movement of phospholipids, thereby stabilizing the membrane.
,3. The sodium-potassium pump (Na+/K+ ATPase) is an example of:
A. Passive diffusion
B. Primary active transport
C. Secondary active transport
D. Facilitated diffusion
Answer: B
Explanation: The Na+/K+ pump uses ATP directly to move ions against their
electrochemical gradients, making it a primary active transporter.
4. Which molecule is most likely to cross a lipid bilayer via simple diffusion?
A. Glucose
B. Oxygen (O2)
C. Sodium ion (Na+)
D. DNA
Answer: B
Explanation: Small, nonpolar molecules like oxygen and carbon dioxide can pass directly
through the hydrophobic core of the lipid bilayer.
5. For every ATP molecule hydrolyzed by the Na+/K+ pump, how many ions are
moved?
A. 3 Na+ out, 2 K+ in
B. 2 Na+ out, 3 K+ in
C. 3 Na+ in, 2 K+ out
D. 1 Na+ out, 1 K+ in
Answer: A
Explanation: The pump exports 3 sodium ions and imports 2 potassium ions per ATP
cycle, contributing to the membrane potential.
, 6. Which type of membrane protein is characterized by having one or more
segments embedded in the hydrophobic core of the bilayer?
A. Peripheral protein
B. Extracellular matrix protein
C. Lipid-anchored protein
D. Integral protein
Answer: D
Explanation: Integral membrane proteins are directly inserted into the lipid bilayer and
usually contain alpha-helical transmembrane domains.
7. The movement of water across a semi-permeable membrane from a region of
low solute concentration to high solute concentration is called:
A. Osmosis
B. Active transport
C. Phagocytosis
D. Pinocytosis
Answer: A
Explanation: Osmosis is the specific term for the passive diffusion of water down its
concentration gradient across a membrane.
8. In a hypertonic solution, a typical animal cell will:
A. Swell and potentially burst
B. Remain unchanged
C. Shrink (crenate)
D. Divide rapidly
Answer: C
Explanation: A hypertonic solution has a higher solute concentration than the cell, causing
water to leave the cell and the cell to shrink.
100% Correct - Florida Gulf Coast University
1. Which of the following factors would most likely increase the fluidity of a lipid
bilayer?
A. A higher concentration of saturated fatty acid tails
B. Decreased temperature
C. Longer fatty acid chain lengths
D. A higher concentration of unsaturated fatty acid tails
E. None of the above
Answer: D
Explanation: Unsaturated fatty acid tails have kinks that prevent tight packing, thereby
increasing membrane fluidity, especially at lower temperatures.
2. What is the primary role of cholesterol in animal cell membranes at high
temperatures?
A. To increase fluidity by creating gaps
B. To make the membrane more permeable to ions
C. To stabilize the membrane and decrease fluidity
D. To synthesize ATP
Answer: C
Explanation: Cholesterol acts as a fluidity buffer; at high temperatures, it restricts the
movement of phospholipids, thereby stabilizing the membrane.
,3. The sodium-potassium pump (Na+/K+ ATPase) is an example of:
A. Passive diffusion
B. Primary active transport
C. Secondary active transport
D. Facilitated diffusion
Answer: B
Explanation: The Na+/K+ pump uses ATP directly to move ions against their
electrochemical gradients, making it a primary active transporter.
4. Which molecule is most likely to cross a lipid bilayer via simple diffusion?
A. Glucose
B. Oxygen (O2)
C. Sodium ion (Na+)
D. DNA
Answer: B
Explanation: Small, nonpolar molecules like oxygen and carbon dioxide can pass directly
through the hydrophobic core of the lipid bilayer.
5. For every ATP molecule hydrolyzed by the Na+/K+ pump, how many ions are
moved?
A. 3 Na+ out, 2 K+ in
B. 2 Na+ out, 3 K+ in
C. 3 Na+ in, 2 K+ out
D. 1 Na+ out, 1 K+ in
Answer: A
Explanation: The pump exports 3 sodium ions and imports 2 potassium ions per ATP
cycle, contributing to the membrane potential.
, 6. Which type of membrane protein is characterized by having one or more
segments embedded in the hydrophobic core of the bilayer?
A. Peripheral protein
B. Extracellular matrix protein
C. Lipid-anchored protein
D. Integral protein
Answer: D
Explanation: Integral membrane proteins are directly inserted into the lipid bilayer and
usually contain alpha-helical transmembrane domains.
7. The movement of water across a semi-permeable membrane from a region of
low solute concentration to high solute concentration is called:
A. Osmosis
B. Active transport
C. Phagocytosis
D. Pinocytosis
Answer: A
Explanation: Osmosis is the specific term for the passive diffusion of water down its
concentration gradient across a membrane.
8. In a hypertonic solution, a typical animal cell will:
A. Swell and potentially burst
B. Remain unchanged
C. Shrink (crenate)
D. Divide rapidly
Answer: C
Explanation: A hypertonic solution has a higher solute concentration than the cell, causing
water to leave the cell and the cell to shrink.
