WGU C785 Biochemistry Unit Exam Actual Exam 2026/2027 –
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Section A: Cellular Structure, Membranes, & Transport (6 Questions)
Q1: A pre-nursing student is observing a patient receiving IV fluids. The nurse explains
that the 0.9% NaCl solution is isotonic to prevent cell lysis. Which cellular transport
mechanism is primarily responsible for maintaining this osmotic balance when water
moves across the erythrocyte membrane?
A. Primary active transport via the Na⁺/K⁺-ATPase pump [CORRECT]
B. Facilitated diffusion through aquaporin channels
C. Simple diffusion of water across the lipid bilayer
D. Secondary active transport via the Na⁺/glucose symporter
Correct Answer: A
Rationale: The Na⁺/K⁺-ATPase pump (primary active transport) maintains the ionic
gradients that drive osmotic balance; by pumping 3 Na⁺ out and 2 K⁺ in, it prevents
cellular swelling and maintains membrane potential. While aquaporins (B) facilitate
water movement, they do not actively regulate osmotic balance. Simple diffusion (C) is
too slow for rapid osmotic adjustments. The Na⁺/glucose symporter (D) is secondary
active transport for nutrient uptake, not osmotic regulation.
,Q2: A patient with cystic fibrosis has a mutation in the CFTR protein, an integral
membrane protein. Which structural feature correctly distinguishes integral proteins like
CFTR from peripheral membrane proteins?
A. Integral proteins are loosely attached to the membrane surface via ionic interactions
B. Integral proteins possess hydrophobic transmembrane domains that span the
phospholipid bilayer [CORRECT]
C. Integral proteins can be easily removed by altering pH or salt concentration
D. Integral proteins lack tertiary structure and function only as structural anchors
Correct Answer: B
Rationale: Integral proteins like CFTR contain hydrophobic alpha-helical transmembrane
domains that embed within the lipid bilayer's hydrophobic core, requiring detergents for
removal. Peripheral proteins (A, C) bind via ionic interactions to membrane surfaces and
are easily stripped by pH/salt changes. Integral proteins have complex
tertiary/quaternary structures and diverse functions including transport and signaling (D
is incorrect).
Q3: A diabetic patient presents with severe hyperglycemia (glucose 450 mg/dL). Which
transport mechanism would be MOST affected, given that glucose entry into most cells
occurs down its concentration gradient with protein assistance but without direct ATP
hydrolysis?
A. Primary active transport
B. Facilitated diffusion via GLUT transporters [CORRECT]
C. Simple diffusion across the phospholipid bilayer
, D. Secondary active transport via SGLT1
Correct Answer: B
Rationale: GLUT (glucose transporter) proteins mediate facilitated diffusion of glucose
down its concentration gradient without ATP hydrolysis; in hyperglycemia, these
transporters become saturated and cannot lower blood glucose effectively. Primary
active transport (A) requires direct ATP use. Simple diffusion (C) is negligible for
glucose due to its polarity. SGLT1 (D) is secondary active transport found mainly in
intestinal/absorptive cells, not most body cells.
Q4: A cell biologist treats a membrane preparation with a non-ionic detergent and
observes that a specific protein remains attached. This protein most likely functions as
which component of the fluid mosaic model?
A. A peripheral protein anchored by phosphatidylinositol linkages
B. An integral membrane protein with multiple transmembrane helices [CORRECT]
C. A lipid-anchored protein on the extracellular leaflet
D. A peripheral protein bound to integral protein cytoplasmic domains
Correct Answer: B
Rationale: Integral membrane proteins with multiple transmembrane helices are deeply
embedded in the hydrophobic core and resist non-ionic detergent extraction, unlike
peripheral proteins (A, D) which are removed by mild treatments. Lipid-anchored
proteins (C) are also detergent-soluble. The fluid mosaic model describes proteins as
mobile within the bilayer, with integral proteins spanning the membrane.
Complete Solution Set with Detailed Rationales | 100%
Verified | Pass Guaranteed – A+ Graded
Section A: Cellular Structure, Membranes, & Transport (6 Questions)
Q1: A pre-nursing student is observing a patient receiving IV fluids. The nurse explains
that the 0.9% NaCl solution is isotonic to prevent cell lysis. Which cellular transport
mechanism is primarily responsible for maintaining this osmotic balance when water
moves across the erythrocyte membrane?
A. Primary active transport via the Na⁺/K⁺-ATPase pump [CORRECT]
B. Facilitated diffusion through aquaporin channels
C. Simple diffusion of water across the lipid bilayer
D. Secondary active transport via the Na⁺/glucose symporter
Correct Answer: A
Rationale: The Na⁺/K⁺-ATPase pump (primary active transport) maintains the ionic
gradients that drive osmotic balance; by pumping 3 Na⁺ out and 2 K⁺ in, it prevents
cellular swelling and maintains membrane potential. While aquaporins (B) facilitate
water movement, they do not actively regulate osmotic balance. Simple diffusion (C) is
too slow for rapid osmotic adjustments. The Na⁺/glucose symporter (D) is secondary
active transport for nutrient uptake, not osmotic regulation.
,Q2: A patient with cystic fibrosis has a mutation in the CFTR protein, an integral
membrane protein. Which structural feature correctly distinguishes integral proteins like
CFTR from peripheral membrane proteins?
A. Integral proteins are loosely attached to the membrane surface via ionic interactions
B. Integral proteins possess hydrophobic transmembrane domains that span the
phospholipid bilayer [CORRECT]
C. Integral proteins can be easily removed by altering pH or salt concentration
D. Integral proteins lack tertiary structure and function only as structural anchors
Correct Answer: B
Rationale: Integral proteins like CFTR contain hydrophobic alpha-helical transmembrane
domains that embed within the lipid bilayer's hydrophobic core, requiring detergents for
removal. Peripheral proteins (A, C) bind via ionic interactions to membrane surfaces and
are easily stripped by pH/salt changes. Integral proteins have complex
tertiary/quaternary structures and diverse functions including transport and signaling (D
is incorrect).
Q3: A diabetic patient presents with severe hyperglycemia (glucose 450 mg/dL). Which
transport mechanism would be MOST affected, given that glucose entry into most cells
occurs down its concentration gradient with protein assistance but without direct ATP
hydrolysis?
A. Primary active transport
B. Facilitated diffusion via GLUT transporters [CORRECT]
C. Simple diffusion across the phospholipid bilayer
, D. Secondary active transport via SGLT1
Correct Answer: B
Rationale: GLUT (glucose transporter) proteins mediate facilitated diffusion of glucose
down its concentration gradient without ATP hydrolysis; in hyperglycemia, these
transporters become saturated and cannot lower blood glucose effectively. Primary
active transport (A) requires direct ATP use. Simple diffusion (C) is negligible for
glucose due to its polarity. SGLT1 (D) is secondary active transport found mainly in
intestinal/absorptive cells, not most body cells.
Q4: A cell biologist treats a membrane preparation with a non-ionic detergent and
observes that a specific protein remains attached. This protein most likely functions as
which component of the fluid mosaic model?
A. A peripheral protein anchored by phosphatidylinositol linkages
B. An integral membrane protein with multiple transmembrane helices [CORRECT]
C. A lipid-anchored protein on the extracellular leaflet
D. A peripheral protein bound to integral protein cytoplasmic domains
Correct Answer: B
Rationale: Integral membrane proteins with multiple transmembrane helices are deeply
embedded in the hydrophobic core and resist non-ionic detergent extraction, unlike
peripheral proteins (A, D) which are removed by mild treatments. Lipid-anchored
proteins (C) are also detergent-soluble. The fluid mosaic model describes proteins as
mobile within the bilayer, with integral proteins spanning the membrane.
