D103 Biology Exam Questions with Correct
Answers
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?
A: Na+ diffused out
B: Cl- diffused out
C: H2O diffused in
D: Glucose diffused out
E: Nothing happens
C. H2O diffused in
. 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
B. can only mediate passive transport
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
D. A molecule of glucose
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+
D: The channel will stay in an open conformation
E: The channel will not open when acetylcholine is present
E. The channel will not open when acetylcholine is present
You have identified a novel sodium channel: this protein forms a homo-tetramer, with
each subunit containing 5 transmembrane domains. How many hydrophobic domains
to 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
A. 5
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
C. generates a proton gradient across the inner mito membrane
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
A. It is circular
Which of the following statements best describes a factor(s) that is required for efficient
ATP synthesis by mitochondria? (mito: mitochondria)
A: An ATP-driven proton pump in the inner mito membrane.
, B: An electron gradient across the inner mito membrane.
C: The Na+/K+ pump, which establishes an electrochemical gradient for Na+, that then
drives proton movement.
D: A proton gradient and membrane potential across the outer mito membrane.
E: A steep electrochemical gradient for protons, made up of a pH gradient and a
membrane potential across the inner mito membrane
E. A steep electrochemical gradient for protons, made up of a pH gradient and a membrane
potential across the inner mito membrane
Immunofluorescence analysis of mitochondria in control and mutant cells gives you the
following images. Mitochondria in wildtype cells are more linear than those in mutant
cells. Which of the following proteins is most likely defective in this
mutant?Mitochondrial protein TOM20 is labeled in red. (Tip: Check the ALS3 slide
"Mitochondrial organization is highly dynamic")
A: ATP Synthase
B: A mitochondrial fusion factor
C: A mitochondrial fission factor
D: A complex I component
E: a TCA cycle enzyme
B. mitochondrial fusion factor
In an in vitro polymerization reaction of F-actin from its G-actin subunits, there is a lag
phase (rate-limiting stage). What happens during this lag phase?
A: F-actin is nucleated
Answers
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?
A: Na+ diffused out
B: Cl- diffused out
C: H2O diffused in
D: Glucose diffused out
E: Nothing happens
C. H2O diffused in
. 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
B. can only mediate passive transport
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
D. A molecule of glucose
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+
D: The channel will stay in an open conformation
E: The channel will not open when acetylcholine is present
E. The channel will not open when acetylcholine is present
You have identified a novel sodium channel: this protein forms a homo-tetramer, with
each subunit containing 5 transmembrane domains. How many hydrophobic domains
to 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
A. 5
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
C. generates a proton gradient across the inner mito membrane
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
A. It is circular
Which of the following statements best describes a factor(s) that is required for efficient
ATP synthesis by mitochondria? (mito: mitochondria)
A: An ATP-driven proton pump in the inner mito membrane.
, B: An electron gradient across the inner mito membrane.
C: The Na+/K+ pump, which establishes an electrochemical gradient for Na+, that then
drives proton movement.
D: A proton gradient and membrane potential across the outer mito membrane.
E: A steep electrochemical gradient for protons, made up of a pH gradient and a
membrane potential across the inner mito membrane
E. A steep electrochemical gradient for protons, made up of a pH gradient and a membrane
potential across the inner mito membrane
Immunofluorescence analysis of mitochondria in control and mutant cells gives you the
following images. Mitochondria in wildtype cells are more linear than those in mutant
cells. Which of the following proteins is most likely defective in this
mutant?Mitochondrial protein TOM20 is labeled in red. (Tip: Check the ALS3 slide
"Mitochondrial organization is highly dynamic")
A: ATP Synthase
B: A mitochondrial fusion factor
C: A mitochondrial fission factor
D: A complex I component
E: a TCA cycle enzyme
B. mitochondrial fusion factor
In an in vitro polymerization reaction of F-actin from its G-actin subunits, there is a lag
phase (rate-limiting stage). What happens during this lag phase?
A: F-actin is nucleated
