1
WGU D402 Study Guide for OA from PA
Actual Exam 2026/2027 – Complete Exam-
Style Questions with Detailed Rationales |
Pass Guaranteed – A+ Graded
[SECTION 1: Cell Biology & Cell Membranes — Questions 1-14]
Q1: Which of the following structures is found in prokaryotic cells but is absent in eukaryotic
cells?
A. A cell membrane composed of a phospholipid bilayer.
B. Ribosomes responsible for protein synthesis.
C. A nucleoid region where the circular DNA is located. [CORRECT]
D. Cytoplasm where metabolic reactions occur.
Correct Answer: C
Rationale: Prokaryotic cells lack a membrane-bound nucleus; instead, their DNA is concentrated
in a region called the nucleoid. While both prokaryotic and eukaryotic cells possess cell
membranes, ribosomes, and cytoplasm, the nucleoid is a distinguishing feature of prokaryotes.
Options A, B, and D describe structures universal to almost all living cells.
Q2: A researcher observes a cell under a microscope and notes the presence of a cell wall made
of peptidoglycan. To which domain does this cell most likely belong?
A. Domain Eukarya
B. Domain Bacteria [CORRECT]
C. Domain Archaea
D. Domain Protista
Correct Answer: B
,2
Rationale: Peptidoglycan is a unique polymer found in the cell walls of bacteria, making it a key
diagnostic feature for Domain Bacteria. Archaea have cell walls that lack peptidoglycan (often
containing pseudomurein or S-layers), and Eukarya generally have cell walls made of cellulose
(plants), chitin (fungi), or lack cell walls entirely (animals). Option D is not a domain but a
kingdom within Eukarya.
Q3: Which organelle contains its own circular DNA and 70S ribosomes, supporting the
endosymbiotic theory?
A. Golgi apparatus
B. Mitochondrion [CORRECT]
C. Smooth endoplasmic reticulum
D. Lysosome
Correct Answer: B
Rationale: The endosymbiotic theory posits that mitochondria originated from free-living
prokaryotes engulfed by a host cell. Evidence for this includes mitochondria possessing their
own DNA (similar to bacterial chromosomes) and 70S ribosomes (characteristic of prokaryotes,
not the 80S ribosomes found in the eukaryotic cytoplasm). The Golgi, SER, and lysosomes do
not possess independent genetic material.
Q4: In the fluid mosaic model of the cell membrane, which type of protein spans the entire width
of the bilayer and typically functions as a channel or carrier?
A. Peripheral protein
B. Integral protein [CORRECT]
C. Surface protein
D. Glycoprotein
Correct Answer: B
Rationale: Integral proteins (specifically transmembrane proteins) penetrate through the
hydrophobic core of the lipid bilayer, often facilitating the transport of molecules that cannot
pass directly through the membrane. Peripheral proteins are loosely attached to the surface of the
, 3
membrane (either interior or exterior) and do not span the bilayer. Glycoproteins can be either
integral or peripheral, defined by their carbohydrate chain.
Q5: If a red blood cell is placed in a hypertonic solution, what will happen to the cell?
A. It will swell and potentially burst (lyse).
B. It will remain the same size because the solution is isotonic.
C. It will shrivel (crenate) as water moves out of the cell. [CORRECT]
D. It will actively transport salts into the cell to balance the solution.
Correct Answer: C
Rationale: In a hypertonic solution, the solute concentration outside the cell is higher than inside,
causing water to diffuse out of the cell via osmosis to equalize the concentration. The loss of
water causes the red blood cell to shrink and shrivel. Option A describes a hypotonic
environment, and Option B describes an isotonic environment; active transport (Option D) is not
the immediate response to osmotic pressure in this context.
Q6: Which of the following processes requires the input of ATP (energy) to move molecules
against their concentration gradient?
A. Simple diffusion
B. Facilitated diffusion
C. Osmosis
D. Active transport [CORRECT]
Correct Answer: D
Rationale: Active transport is the movement of molecules from an area of low concentration to
an area of high concentration (against the gradient), which requires energy (ATP) because it
opposes natural thermodynamic flow. Simple diffusion, facilitated diffusion, and osmosis are all
forms of passive transport that move substances down their concentration gradient without
energy input.
WGU D402 Study Guide for OA from PA
Actual Exam 2026/2027 – Complete Exam-
Style Questions with Detailed Rationales |
Pass Guaranteed – A+ Graded
[SECTION 1: Cell Biology & Cell Membranes — Questions 1-14]
Q1: Which of the following structures is found in prokaryotic cells but is absent in eukaryotic
cells?
A. A cell membrane composed of a phospholipid bilayer.
B. Ribosomes responsible for protein synthesis.
C. A nucleoid region where the circular DNA is located. [CORRECT]
D. Cytoplasm where metabolic reactions occur.
Correct Answer: C
Rationale: Prokaryotic cells lack a membrane-bound nucleus; instead, their DNA is concentrated
in a region called the nucleoid. While both prokaryotic and eukaryotic cells possess cell
membranes, ribosomes, and cytoplasm, the nucleoid is a distinguishing feature of prokaryotes.
Options A, B, and D describe structures universal to almost all living cells.
Q2: A researcher observes a cell under a microscope and notes the presence of a cell wall made
of peptidoglycan. To which domain does this cell most likely belong?
A. Domain Eukarya
B. Domain Bacteria [CORRECT]
C. Domain Archaea
D. Domain Protista
Correct Answer: B
,2
Rationale: Peptidoglycan is a unique polymer found in the cell walls of bacteria, making it a key
diagnostic feature for Domain Bacteria. Archaea have cell walls that lack peptidoglycan (often
containing pseudomurein or S-layers), and Eukarya generally have cell walls made of cellulose
(plants), chitin (fungi), or lack cell walls entirely (animals). Option D is not a domain but a
kingdom within Eukarya.
Q3: Which organelle contains its own circular DNA and 70S ribosomes, supporting the
endosymbiotic theory?
A. Golgi apparatus
B. Mitochondrion [CORRECT]
C. Smooth endoplasmic reticulum
D. Lysosome
Correct Answer: B
Rationale: The endosymbiotic theory posits that mitochondria originated from free-living
prokaryotes engulfed by a host cell. Evidence for this includes mitochondria possessing their
own DNA (similar to bacterial chromosomes) and 70S ribosomes (characteristic of prokaryotes,
not the 80S ribosomes found in the eukaryotic cytoplasm). The Golgi, SER, and lysosomes do
not possess independent genetic material.
Q4: In the fluid mosaic model of the cell membrane, which type of protein spans the entire width
of the bilayer and typically functions as a channel or carrier?
A. Peripheral protein
B. Integral protein [CORRECT]
C. Surface protein
D. Glycoprotein
Correct Answer: B
Rationale: Integral proteins (specifically transmembrane proteins) penetrate through the
hydrophobic core of the lipid bilayer, often facilitating the transport of molecules that cannot
pass directly through the membrane. Peripheral proteins are loosely attached to the surface of the
, 3
membrane (either interior or exterior) and do not span the bilayer. Glycoproteins can be either
integral or peripheral, defined by their carbohydrate chain.
Q5: If a red blood cell is placed in a hypertonic solution, what will happen to the cell?
A. It will swell and potentially burst (lyse).
B. It will remain the same size because the solution is isotonic.
C. It will shrivel (crenate) as water moves out of the cell. [CORRECT]
D. It will actively transport salts into the cell to balance the solution.
Correct Answer: C
Rationale: In a hypertonic solution, the solute concentration outside the cell is higher than inside,
causing water to diffuse out of the cell via osmosis to equalize the concentration. The loss of
water causes the red blood cell to shrink and shrivel. Option A describes a hypotonic
environment, and Option B describes an isotonic environment; active transport (Option D) is not
the immediate response to osmotic pressure in this context.
Q6: Which of the following processes requires the input of ATP (energy) to move molecules
against their concentration gradient?
A. Simple diffusion
B. Facilitated diffusion
C. Osmosis
D. Active transport [CORRECT]
Correct Answer: D
Rationale: Active transport is the movement of molecules from an area of low concentration to
an area of high concentration (against the gradient), which requires energy (ATP) because it
opposes natural thermodynamic flow. Simple diffusion, facilitated diffusion, and osmosis are all
forms of passive transport that move substances down their concentration gradient without
energy input.
