Biology 111 – Exam 2
BIOLOGY 111 EXAM 2 | QUESTIONS AND 100% CORRECT ANSWERS |
LATEST 2026/2027
BIOLOGY 111 – EXAM 2
1. Which molecule forms the basic structural framework of the plasma
membrane?
A. Cellulose microfibrils
B. Phospholipid bilayer
C. Triglyceride droplets
D. Double-stranded DNA
B. Phospholipid bilayer. Phospholipids self-assemble into a bilayer with
hydrophilic heads outward and hydrophobic tails inward.
2. Which part of a phospholipid is hydrophobic?
A. The fatty acid tails
B. The phosphate head
C. The choline group
D. The glycerol backbone
A. The fatty acid tails. The nonpolar hydrocarbon tails avoid water and
face the membrane interior.
Page 1 of 44
, Biology 111 – Exam 2
3. The fluid mosaic model describes the membrane as
A. A static wall of carbohydrates
B. A single layer of phospholipids
C. A fluid lipid bilayer with proteins embedded or attached
D. A rigid layer of protein with lipids on top
C. A fluid lipid bilayer with proteins embedded or attached. Lipids and
proteins move laterally, giving the membrane a fluid, mosaic-like
character.
4. What is the main role of cholesterol in animal cell membranes?
A. It synthesizes ATP
B. It acts as a receptor for hormones
C. It transports ions across the membrane
D. It buffers membrane fluidity across temperature changes
D. It buffers membrane fluidity across temperature changes. Cholesterol
restrains movement at high temperatures and prevents tight packing at
low temperatures.
5. Integral membrane proteins differ from peripheral proteins because
integral proteins
A. Are found only in the cytoplasm
B. Never interact with lipids
C. Are made only of carbohydrate
D. Are embedded in or span the lipid bilayer
D. Are embedded in or span the lipid bilayer. Integral proteins have
hydrophobic regions that sit within the bilayer; peripheral proteins
attach loosely to the surface.
6. Which of the following can cross the phospholipid bilayer most easily
by simple diffusion?
A. Oxygen
B. Sodium ions
C. Large proteins
D. Glucose
A. Oxygen. Small nonpolar molecules like O2 dissolve in the hydrophobic
core and pass freely.
Page 2 of 44
, Biology 111 – Exam 2
7. Glycoproteins on the outer surface of the plasma membrane are
mainly involved in
A. DNA replication
B. Cell-cell recognition
C. Ribosome assembly
D. Energy storage
B. Cell-cell recognition. Carbohydrate chains on membrane proteins act
as identification tags between cells.
8. Diffusion of a substance across a membrane requires no cellular
energy because it moves
A. Only through ATP-driven pumps
B. Against its concentration gradient
C. Down its concentration gradient
D. Only through vesicles
C. Down its concentration gradient. Passive transport follows the
gradient from high to low concentration.
9. Osmosis is best defined as the movement of
A. Proteins into the nucleus
B. Water across a selectively permeable membrane
C. Lipids between organelles
D. Solute across a membrane using ATP
B. Water across a selectively permeable membrane. Water moves
toward the region of higher solute concentration.
10. A red blood cell placed in a hypotonic solution will
A. Divide rapidly
B. Shrink and crenate
C. Stay exactly the same size
D. Swell and possibly burst
D. Swell and possibly burst. Water enters the cell because the outside
solution has a lower solute concentration.
Page 3 of 44
, Biology 111 – Exam 2
11. A plant cell in a hypertonic solution undergoes
A. Turgor pressure increase
B. Lysis
C. Endocytosis
D. Plasmolysis
D. Plasmolysis. Water leaves, and the plasma membrane pulls away from
the cell wall.
12. A plant cell is most firm and healthy when placed in a
A. Hypertonic solution
B. Isotonic solution
C. Saturated salt solution
D. Hypotonic solution
D. Hypotonic solution. Water enters and the cell wall resists, producing
strong turgor pressure.
13. Which term describes a solution with the same solute concentration
as the cell's cytoplasm?
A. Hypertonic
B. Hypotonic
C. Isotonic
D. Hyperbaric
C. Isotonic. Isotonic solutions produce no net water movement.
14. Facilitated diffusion differs from simple diffusion because it
A. Requires ATP
B. Moves solutes against a gradient
C. Occurs only in bacteria
D. Uses channel or carrier proteins
D. Uses channel or carrier proteins. Polar molecules and ions need
transport proteins but still move down their gradient.
15. Aquaporins are channel proteins that specifically allow passage of
A. Glucose
B. Water
C. Sodium ions
D. Amino acids
B. Water. Aquaporins greatly increase membrane permeability to water.
Page 4 of 44
BIOLOGY 111 EXAM 2 | QUESTIONS AND 100% CORRECT ANSWERS |
LATEST 2026/2027
BIOLOGY 111 – EXAM 2
1. Which molecule forms the basic structural framework of the plasma
membrane?
A. Cellulose microfibrils
B. Phospholipid bilayer
C. Triglyceride droplets
D. Double-stranded DNA
B. Phospholipid bilayer. Phospholipids self-assemble into a bilayer with
hydrophilic heads outward and hydrophobic tails inward.
2. Which part of a phospholipid is hydrophobic?
A. The fatty acid tails
B. The phosphate head
C. The choline group
D. The glycerol backbone
A. The fatty acid tails. The nonpolar hydrocarbon tails avoid water and
face the membrane interior.
Page 1 of 44
, Biology 111 – Exam 2
3. The fluid mosaic model describes the membrane as
A. A static wall of carbohydrates
B. A single layer of phospholipids
C. A fluid lipid bilayer with proteins embedded or attached
D. A rigid layer of protein with lipids on top
C. A fluid lipid bilayer with proteins embedded or attached. Lipids and
proteins move laterally, giving the membrane a fluid, mosaic-like
character.
4. What is the main role of cholesterol in animal cell membranes?
A. It synthesizes ATP
B. It acts as a receptor for hormones
C. It transports ions across the membrane
D. It buffers membrane fluidity across temperature changes
D. It buffers membrane fluidity across temperature changes. Cholesterol
restrains movement at high temperatures and prevents tight packing at
low temperatures.
5. Integral membrane proteins differ from peripheral proteins because
integral proteins
A. Are found only in the cytoplasm
B. Never interact with lipids
C. Are made only of carbohydrate
D. Are embedded in or span the lipid bilayer
D. Are embedded in or span the lipid bilayer. Integral proteins have
hydrophobic regions that sit within the bilayer; peripheral proteins
attach loosely to the surface.
6. Which of the following can cross the phospholipid bilayer most easily
by simple diffusion?
A. Oxygen
B. Sodium ions
C. Large proteins
D. Glucose
A. Oxygen. Small nonpolar molecules like O2 dissolve in the hydrophobic
core and pass freely.
Page 2 of 44
, Biology 111 – Exam 2
7. Glycoproteins on the outer surface of the plasma membrane are
mainly involved in
A. DNA replication
B. Cell-cell recognition
C. Ribosome assembly
D. Energy storage
B. Cell-cell recognition. Carbohydrate chains on membrane proteins act
as identification tags between cells.
8. Diffusion of a substance across a membrane requires no cellular
energy because it moves
A. Only through ATP-driven pumps
B. Against its concentration gradient
C. Down its concentration gradient
D. Only through vesicles
C. Down its concentration gradient. Passive transport follows the
gradient from high to low concentration.
9. Osmosis is best defined as the movement of
A. Proteins into the nucleus
B. Water across a selectively permeable membrane
C. Lipids between organelles
D. Solute across a membrane using ATP
B. Water across a selectively permeable membrane. Water moves
toward the region of higher solute concentration.
10. A red blood cell placed in a hypotonic solution will
A. Divide rapidly
B. Shrink and crenate
C. Stay exactly the same size
D. Swell and possibly burst
D. Swell and possibly burst. Water enters the cell because the outside
solution has a lower solute concentration.
Page 3 of 44
, Biology 111 – Exam 2
11. A plant cell in a hypertonic solution undergoes
A. Turgor pressure increase
B. Lysis
C. Endocytosis
D. Plasmolysis
D. Plasmolysis. Water leaves, and the plasma membrane pulls away from
the cell wall.
12. A plant cell is most firm and healthy when placed in a
A. Hypertonic solution
B. Isotonic solution
C. Saturated salt solution
D. Hypotonic solution
D. Hypotonic solution. Water enters and the cell wall resists, producing
strong turgor pressure.
13. Which term describes a solution with the same solute concentration
as the cell's cytoplasm?
A. Hypertonic
B. Hypotonic
C. Isotonic
D. Hyperbaric
C. Isotonic. Isotonic solutions produce no net water movement.
14. Facilitated diffusion differs from simple diffusion because it
A. Requires ATP
B. Moves solutes against a gradient
C. Occurs only in bacteria
D. Uses channel or carrier proteins
D. Uses channel or carrier proteins. Polar molecules and ions need
transport proteins but still move down their gradient.
15. Aquaporins are channel proteins that specifically allow passage of
A. Glucose
B. Water
C. Sodium ions
D. Amino acids
B. Water. Aquaporins greatly increase membrane permeability to water.
Page 4 of 44
