WGU D103 MIDTERM 1 EXAM 2025/2026
QUESTIONS AND ANSWERS 100% PASS
Which factors are likely to lead to a decrease in membrane fluidity?
A: An increase in the number of unsaturated bonds in the hydrophobic tail of phospholipids
B: An increase in the activity of a transmembrane protein
C: A change in the molar ratio of PC to PE
D: An increase in the number of phospholipids with long hydrophobic tails - ANS D
Which of the following organisms is most likely to have the highest percentage of unsaturated
fatty acid chains in their membranes?
A: Antarctic bacterium
B: Desert iguana
C: Human being
D: Polar bear
E: Thermophilic bacterium - ANS A
Why is cholesterol able to integrate into a lipid bilayer?
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,A: Because it is a small molecule
B: Because it is a fully hydrophobic molecule
C: Because it is abundant
D: Because it has an amphipathic organization, similar to membrane lipids
E: Because it can bind covalently to phospholipids - ANS D
Which of the following statement best describes how bacteria in a hot spring control the
fluidity of their plasma membrane?
A: They decrease the percentage of lipids with unsaturated fatty acid tails in their plasma
membrane
B: Because they don't synthesize cholesterol, they cannot control membrane fluidity and
therefore have a very fluid plasma membrane.
C: They reduce cholesterol production to prevent membranes from becoming too fluid.
D: They form lipid rafts in their membranes to prevent too much fluidity
E: They increase the percentage of lipids with unsaturated fatty acid tails in their plasma
membrane - ANS E
Which information can you obtain from a hydrophobicity plot?
A: The number of potential hydrophobic transmembrane domain
B: The topology of the protein
C: Where the protein localizes in the cell
D: Its interaction partner
E: The protein's function - ANS A
Imagine a small synthetic vesicle made from pure phospholipids (formed as lipid bilayer). Its
lumen contains 1 mM Glucose and 1 mM sodium chloride (NaCl). If the vesicle is placed in pure
water, which of the following happens the fastest?
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,A: Na+ diffused out
B: Cl- diffused out
C: H2O diffused in
D: Glucose diffused out
E: Nothing happens - ANS C
In contrast to transporters, channel proteins in cellular membrane:
A: Undergo a conformational change every time they transport an ion solute
B: Can only mediate passive transport
C: Form pores that are always open
D: Are always controlled by voltage - ANS B
Which of the following molecules is most likely to induce a conformational change in a
uniporter that transports glucose across the plasma membrane?
A: An extracellular ligand
B: An intracellular ligand
C: There is no need for a ligand, as the transporter changes conformation spontaneously
D: A molecule of glucose
E: A Na+ ion - ANS D
What is the most likely consequence of a mutation in the acetylcholine binding site of an
acetylcholine-gated Na+ channel in the post-synaptic nerve terminal? (Note: This mutation
prevents the binding of acetylcholine to the channel)
A: There is no effect
B: The channel will not insert properly into the membrane
C: The channel will now transport K+
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, D: The channel will stay in an open conformation
E: The channel will not open when acetylcholine is present - ANS E
You have identified a novel sodium channel: this protein forms a homo-tetramer, with each
subunit containing 5 transmembrane domains. How many hydrophobic domains do you predict
to see in a hydrophobicity plot of this sodium channel?
A: 5
B: 10
C: 15
D: 20
E: Hydrophobicity plot cannot be generated for this protein - ANS D
Which of the following statements is most correct? (mito: mitochondria)
The electron transport chain -
A: generates a pH gradient that reduces O2 to H2O
B: generates a proton gradient across the outer mito membrane
C: generates a proton gradient across the inner mito membrane
D: uses the energy stored in high energy electron carriers to synthesize ATP
E: establishes a membrane potential across the outer mito membrane - ANS C
Which of the following statements best describes properties of mitochondrial DNA?
A: It is circular
B: It contains more nucleotides than nuclear DNA
C: It encodes all proteins found in mitochondria
D: It is transported into the cytosol for transcription and translation
E: It is replicated in parallel with nuclear DNA - ANS A
4 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED
QUESTIONS AND ANSWERS 100% PASS
Which factors are likely to lead to a decrease in membrane fluidity?
A: An increase in the number of unsaturated bonds in the hydrophobic tail of phospholipids
B: An increase in the activity of a transmembrane protein
C: A change in the molar ratio of PC to PE
D: An increase in the number of phospholipids with long hydrophobic tails - ANS D
Which of the following organisms is most likely to have the highest percentage of unsaturated
fatty acid chains in their membranes?
A: Antarctic bacterium
B: Desert iguana
C: Human being
D: Polar bear
E: Thermophilic bacterium - ANS A
Why is cholesterol able to integrate into a lipid bilayer?
1 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED
,A: Because it is a small molecule
B: Because it is a fully hydrophobic molecule
C: Because it is abundant
D: Because it has an amphipathic organization, similar to membrane lipids
E: Because it can bind covalently to phospholipids - ANS D
Which of the following statement best describes how bacteria in a hot spring control the
fluidity of their plasma membrane?
A: They decrease the percentage of lipids with unsaturated fatty acid tails in their plasma
membrane
B: Because they don't synthesize cholesterol, they cannot control membrane fluidity and
therefore have a very fluid plasma membrane.
C: They reduce cholesterol production to prevent membranes from becoming too fluid.
D: They form lipid rafts in their membranes to prevent too much fluidity
E: They increase the percentage of lipids with unsaturated fatty acid tails in their plasma
membrane - ANS E
Which information can you obtain from a hydrophobicity plot?
A: The number of potential hydrophobic transmembrane domain
B: The topology of the protein
C: Where the protein localizes in the cell
D: Its interaction partner
E: The protein's function - ANS A
Imagine a small synthetic vesicle made from pure phospholipids (formed as lipid bilayer). Its
lumen contains 1 mM Glucose and 1 mM sodium chloride (NaCl). If the vesicle is placed in pure
water, which of the following happens the fastest?
2 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED
,A: Na+ diffused out
B: Cl- diffused out
C: H2O diffused in
D: Glucose diffused out
E: Nothing happens - ANS C
In contrast to transporters, channel proteins in cellular membrane:
A: Undergo a conformational change every time they transport an ion solute
B: Can only mediate passive transport
C: Form pores that are always open
D: Are always controlled by voltage - ANS B
Which of the following molecules is most likely to induce a conformational change in a
uniporter that transports glucose across the plasma membrane?
A: An extracellular ligand
B: An intracellular ligand
C: There is no need for a ligand, as the transporter changes conformation spontaneously
D: A molecule of glucose
E: A Na+ ion - ANS D
What is the most likely consequence of a mutation in the acetylcholine binding site of an
acetylcholine-gated Na+ channel in the post-synaptic nerve terminal? (Note: This mutation
prevents the binding of acetylcholine to the channel)
A: There is no effect
B: The channel will not insert properly into the membrane
C: The channel will now transport K+
3 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED
, D: The channel will stay in an open conformation
E: The channel will not open when acetylcholine is present - ANS E
You have identified a novel sodium channel: this protein forms a homo-tetramer, with each
subunit containing 5 transmembrane domains. How many hydrophobic domains do you predict
to see in a hydrophobicity plot of this sodium channel?
A: 5
B: 10
C: 15
D: 20
E: Hydrophobicity plot cannot be generated for this protein - ANS D
Which of the following statements is most correct? (mito: mitochondria)
The electron transport chain -
A: generates a pH gradient that reduces O2 to H2O
B: generates a proton gradient across the outer mito membrane
C: generates a proton gradient across the inner mito membrane
D: uses the energy stored in high energy electron carriers to synthesize ATP
E: establishes a membrane potential across the outer mito membrane - ANS C
Which of the following statements best describes properties of mitochondrial DNA?
A: It is circular
B: It contains more nucleotides than nuclear DNA
C: It encodes all proteins found in mitochondria
D: It is transported into the cytosol for transcription and translation
E: It is replicated in parallel with nuclear DNA - ANS A
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