Lecture 12-21 Flashcards
(152 cards)
1
Q
Which of the following proteins are made in the rough endoplasmic reticulum?
a. cytosolic proteins
b. proteins destined for chloroplasts
c. proteins sent to the nucleus
d. proteins sent to lysosomes
e. c and d
A
d
2
Q
- Once an ER-derived vacuole or -cisterna has surrounded an organelle to be destroyed with a double membrane, it fuses with a lysosome. What is the resultant structure called?
a. autophagolysosome
b. phagolysosome
c. bacteriophage
d. phagosome
e. autophagosome
A
a
3
Q
- How are integral membrane proteins distinguished from secretory proteins as they are being synthesized on ribosomes bound to the RER?
a. Integral membrane proteins possess one or more hydrophilic transmembrane segments of amino acids that block further movement of protein into the ER lumen.
b. Integral membrane proteins possess stop-transfer sequences.
c. Integral membrane proteins possess one or more hydrophobic transmembrane segments of amino acids that block further movement of protein into the ER lumen.
d. a and b
e. b and c
A
e
4
Q
- Stop-transfer sequences typically include ___________.
a. at least 15 continuous hydrophobic or uncharged amino acids
b. at least 15 continuous hydrophilic or charged amino acids
c. at least 15 continuous hydrophobic or charged amino acids
d. at least 15 continuous hydrophilic or uncharged amino acids
e. more than one of the above
A
a
5
Q
- Phospholipids are made by integral ER membrane enzymes whose active sites face the cytosol and they are inserted into the outer (cytoplasmic) side of the ER membrane. How then do lipids destined for the luminal side of the ER membrane get there?
a. They diffuse freely into the luminal side.
b. There are enzymes that actively translocate them across the bilayer.
c. They are disassembled on the cytoplasmic side and reassembled on the luminal side.
d. They move to the cytoplasmic side by osmosis.
e. They move to the cytoplasmic side by diffusion.
A
b
6
Q
- Which of the following strategies do bacteria use to avoid being destroyed by a lysosome’s fusion with the phagosome in which it was ingested?
a. The bacterium uses a H+-ATPase to neutralize the acidic environment in the phagolysosome.
b. The bacterium inhibits fusion of the phagosome with a lysosome.
c. The bacterium allows fusion with the lysosome, but neither the acidic pH nor the lysosomal enzymes can destroy it.
d. a and b
e. b and c
A
e
7
Q
- What GTP-binding protein plays a regulatory role in the formation and disassembly of the COPII coat?
a. Sar1
b. Rab
c. ARF1
d. clathrin
e. SNARE
A
a
8
Q
- What is the function of the protein coat on budding vesicles?
a. It acts as a mechanical device that helps to form the vesicle.
b. It provides a mechanism for selecting components and cargo to be carried by each vesicle.
c. It restricts certain molecules from being included in the vesicle.
d. a and b
e. a, b, and c
A
d Note that coat proteins don’t actually control what is packaged into the vesicles; that level of control is mediated by the receptors
9
Q
- Mad cow disease is caused by mutant, misfolded _______________ proteins. These mutant proteins cause damage to neural cells because the protein-degrading machinery, known as the ________________________, is unable to deal with them.
A
prion; proteasome
10
Q
- Which model suggests that the Golgi cisternae are transient structures that form at the cis face and travel through the Golgi complex, moving physically and exiting the organelle at the trans face, while changing during the journey?
A
the cisternal maturation model
11
Q
What is the relevance of mannose-6-phosphate to lysosomes?
a. It is the sugar that lines the interior of a lysosome’s membrane.
b. It is a sugar added to proteins destined to be digested by the lysosomes.
c. It is a receptor for lysosomal lipids.
d. It is a sugar added to proteins that enables them to be transported into lysosomes.
e. It creates an acidic pH environment within the lysosomes.
A
d
12
Q
A mouse fibroblast cell line will grow and divide normally in in vitro cultures at 37ºC. Some of the cells from this culture were subsequently removed and genetically altered such that they now constitutively expressed an antibody that bound to the protein HSP70. This genetically altered cell line, when grown at 37ºC, showed a 40 % reduction in the cell division rate when compared to the unmodified cells. When both the control cells and genetically altered cells were transferred to 42ºC for a period of 3 hours, and then returned to 37ºC, the genetically-altered cells failed to divide any more, while the control cells resumed their cell divisions at the previously observed rate.
The control cells continued to divide after the 43ºC exposure while the genetically engineered cells did not divide because:
a) the genetically-altered cells could not recover from the high temperature while the control cells did recover.
b) the control cells could refold their heat-denatured proteins while the genetically-altered cells could not.
c) the control cells synthesized sufficient chaperone proteins to refold the heat denatured proteins, while the genetically-altered cells did not synthesize enough chaperone proteins.
d) a and b
e) a, b, and c
A
d Note that E is incorrect because the altered cells could still produce normal levels of HSP70, but the antibody that is also produced will interfere with HSP70’s function.
13
Q
The smooth endoplasmic reticulum is involved in what process(es)?
a. synthesis of cytoplasmic proteins
b. synthesis of proteins destined for the lysosomes
c. synthesis of steroids
d. synthesis of endosomal proteins
e. more than one of the above
A
c
14
Q
The lifespan of a protein within a cell can depend upon _______.
a. the identity of its N-terminal amino acid
b. whether it is bound to polyubiquitin
c. whether it is properly folded
d. a and b
e. a, b, and c
A
e
15
Q
The primary site for protein modifications is within the _______ whereas the site for receptor protein recycling is primarily within the __________.
a. endoplasmic reticulum; Golgi
b. Golgi; phagosomes
c. endosomes; lysosomes
d. Golgi; late endosomes
e. lysosomes; primary endosomes
A
d
16
Q
The lifespan of a protein within a cell can depend upon _______.
a. the identity of its N-terminal amino acid
b. whether it is bound to polyubiquitin
c. whether it is properly folded
d. a and b
e. a, b, and c
A
e recall that answer A refers to the N-end rule
17
Q
Which protein is responsible for helping the COP-I protein bind to a budding vesicle?
a. ARF1
b. Sar1
c. SNARE
d. Rab
e. Clathrin
A
a
18
Q
In which of the following processes is a lysosome least likely to be involved?
a. Removal of unneeded cells in a developing embryo
b. Digestion of an extracellular parasite
c. Digestion of polyubiquitinated proteins
d. Egg fertilization
e. Digestion of glycolipids
A
c
19
Q
In which of the following processes is a lysosome least likely to be involved?
a. Removal of unneeded cells in a developing embryo
b. Digestion of an extracellular parasite
c. Digestion of polyubiquitinated proteins
d. Egg fertilization
e. Digestion of glycolipids
A
c recall that polyubiquitin typically guides proteins to the proteasome, not the lysosome
20
Q
A transport system that moves 2 substances into the cell per cycle could be called a(n) _____.
a. uniport
b. antiport
c. symport
d. transmembrane channel
e. biport
A
c
21
Q
- The sodium-potassium pump helps to make the cell interior _________ charged by __________.
a. negatively; pumping negative ions into the cell.
b. negatively; pumping 3 sodium ions out of the cell for every 2 potassium ions pumped in.
c. negatively; pumping 3 potassium ions out of the cell for every 2 sodium ions pumped in.
d. positively; pumping 3 sodium ions into the cell for every 2 potassium ions pumped out.
e. positively; pumping 3 potassium ions into the cell for every 2 sodium ions pumped out.
A
b
22
Q
- What is largely responsible for establishing the resting potential of neurons and other cells?
a. H+/K+ pump
b. Na+/K+pump
c. Ca2+ ATPase
d. Na+/Ca2+ pump
e. Na+ ATPase
A
b
23
Q
- The tendency of an electrolyte to diffuse between two compartments depends upon ________.
a. a chemical or concentration gradient
b. an electric potential gradient
c. an osmotic gradient
d. a and b
e. a, b, and c
A
d
24
Q
- Which of the following statements about lipid rafts is/are correct?
a. Lipid rafts are often enriched with sphingosine.
b. Lipid rafts are often enriched with glycerol.
c. Lipid rafts help cluster integral proteins that work together.
d. a and b.
e. a, b, and c.
A
e
25
6. Which of the following statements about cholesterol is NOT true?
a. At low temperatures, cholesterol increases the fluidity of membranes.
b. Cholesterol is often found concentrated in lipid rafts.
c. At high temperatures, cholesterol decreases fluidity of the membranes.
d. Cholesterol is not found in plant cell membranes.
e. Cholesterol is a lipid common to all animal cells.
d
26
The outward pressure exerted by a plant cell’s membrane on the surrounding cell wall is specifically known as _______.
a. osmotic pressure
b. cytoplasmic pressure
c. turgor pressure
d. plasmolytic pressure
e. cellular pressure
c
27
An amoeba living in freshwater must expel water from its cell using a contractile vacuole. The water enters the vacuole by the process of _______, passing through ________, and is then dumped into the extracellular environment by a process of _______.
a. diffusion; aquaporin channels; endocytosis
b. osmosis; aquaporin channels; exocytosis
c. diffusion; the lipid bilayer; exocytosis
d. active transport; aquaporin channels; exocytosis
e. osmosis; aquaporin channels; endocytosis
b
28
Which of the following compounds cannot cross the cell’s membrane without the aid of carrier or transporter proteins?
a. oxygen
b. glucose
c. water
d. testosterone
e. carbon dioxide
b
29
Which of the following would not occur within a cell’s membrane in an animal preparing for winter hibernation?
a. The cholesterol content of the membranes will increase.
b. There will be increased desaturation of the membrane’s lipids.
c. There will be increased activity of acyltransferases.
d. The fatty acid chains will be lengthened.
e. More double bonds on the lipids’ hydrocarbon tails will occur.
d
30
Which type of membrane pump has been associated with some cancer cells becoming resistant to chemotherapy drugs?
a. P-type ATPase
b. V-type ATP
c. ABC-type ATPase
d. Symport pump
e. Antiport pump
c
31
Sound waves cause cilia on cells within the ear to bend. The bending of the cilia opens ion channels, thereby initiating a change in the electric potential across the cell’s membrane. The initial movement of the ions across the cell’s membrane in response to the cilia’s movement is an example of ___.
a. voltage-gated diffusion
b. voltage-gated active transport
c. facilitated active transport
d. mechanically-gated diffusion
e. ligand-gated transport
d
32
How do cells in the body of a multicellular organism usually communicate with each other?
a. intracellular messenger molecules
b. direct connection by cells through long projections
c. extracellular messenger molecules
d. electrical signals between cells
e. ion transport between cells
c
33
What allows cells to respond to an extracellular messenger molecule?
a. They must have ion channels.
b. They must have a lipid bilayer that allows a response.
c. They must have receptor proteins exposed on the inner plasma membrane surface.
d. They must express transmembrane receptors that specifically recognize and bind that particular messenger molecule.
e. They must have nuclear membranes.
d
34
Where may second messengers be found?
a. diffusing through the cytoplasm
b. in the nuclear membrane
c. embedded in the membrane lipid bilayer
d. a and b
e. a and c
e
35
Where may second messengers be found?
a. diffusing through the cytoplasm
b. in the nuclear membrane
c. embedded in the membrane lipid bilayer
d. a and b
e. a and c
e recall that DAG is embedded in the cell’s plasma membrane
36
What strategies can be used to turn off the cell signaling response when it is necessary to do so?
a. elimination of the extracellular messenger molecule
b. internalization of activated receptors and degradation of the receptor and its ligand
c. internalization of activated receptors and their ligand, degradation of the ligand and return of the receptor to the cell surface
d. degradation of activated signaling proteins
e. all of the above
e
37
If the receptor is degraded along with its ligand after internalization, what is the effect on the cells ability to respond to a hormone?
a. The response is enhanced.
b. The cell has increased sensitivity to subsequent stimuli.
c. The cell has decreased sensitivity to subsequent stimuli.
d. The cell exhibits no change in responsiveness to subsequent stimuli.
e. a and b
c
38
What is the major effect of activated steroid receptor proteins?
a. activation of cell division
b. initiates membrane transport of ions
c. an increase in the rate of gene transcription
d. c and e
e. a decrease in the rate of gene transcription
d
39
What is the major effect of activated steroid receptor proteins?
a. activation of cell division
b. initiates membrane transport of ions
c. an increase in the rate of gene transcription
d. c and e
e. a decrease in the rate of gene transcription
d steroids can bind specific transcription factors – these factors can either increase or decrease gene expression, depending on which response element they bind on the proximal promoter
40
Place the following events in the proper order.
1 – Activation of one or more cellular signaling proteins.
2 – Dissociation of G-alpha from the G protein complex.
3 - Production of a second messenger, like cAMP.
4 – Replacement of GDP by GTP on the G-alpha after interaction with an activated GPCR.
5 – Conformational change in the G-alpha subunit causing a decreased affinity for the G-beta and gamma subunit.
6 - G-alpha subunit with its attached GTP activates an effector like adenylyl cyclase.
a. 4 – 5 – 2 – 6 – 3 – 1
b. 5 – 4 – 2 – 6 – 3 – 1
c. 4 – 6 – 2 – 5 – 3 – 1
d. 4 – 5 – 2 – 3 – 1 – 6
e. 1 – 5 – 2 – 4 – 3 – 6
a
41
How does IP3 get from the plasma membrane where it is made to the receptor on the SER?
a. It is carried there by a transport molecule.
b. It diffuses.
c. It crawls.
d. It osmoses.
e. It is moved enzymatically.
b
42
Both the glucagon and epinephrine receptor ___________.
a. directly activate adenylyl cyclase
b. indirectly activate adenylyl cyclase
c. directly activate the same type of heterotrimeric G protein
d. a and c
e. b and c
e
43
Insulin __________.
a. functions as an extracellular messenger molecule
b. informs the cells of the body that blood-glucose levels are high
c. directly transports glucose into the cell
d. a and b
e. a and c
d
44
The concentration of calcium ions in the ER lumen, the plant cell vacuole and the extracellular space are on average more than _______ times higher than in the cytosol.
a. 10
b. 100
c. 1,000
d. 10,000
e. 1,000,000
d
45
The enzyme that terminates the response to cAMP through the destruction of cAMP molecules present in the cell is called
phosphodiesterase
46
The generic term for an extracellular messenger molecule that binds to transmembrane receptors is a _________________.
ligand
47
In the absence of insulin, where is the GLUT4 glucose transporter generally located?
______________________________
membrane vesicles in the cytoplasm of insulin-responsive cells
48
The enzyme that is, in some cases, activated by a receptor brings about the cellular response by generating a second messenger. Such an enzyme is called a(n) __________.
effector
49
Which statement about heat shock proteins is not correct?
a. Heat shock proteins help refold unfolded proteins following cold stress.
b. Heat shock proteins recognize exposed hydrophilic amino acids on the surface of unfolded proteins.
c. A mild heat shock can result in enhanced cell survival due to accumulation of extra heat shock proteins.
d. Heat shock proteins are sometimes referred to as molecular chaperones.
e. Extra heat shock protein synthesis has been associated with improved tolerance to anoxia.
b
50
Which statement about prions or their associated disorders is not correct?
a. Scrapie is a disease of sheep caused by a misfolded protein.
b. The normal prion protein PrPC is comprised mostly of alpha helices while the mutant prion protein PrPSc is comprised mostly of beta sheets.
c. The PrPC protein and the PrPSc protein have the same primary protein structure.
d. When PrPC protein comes in contact with PrPSc protein, it causes the PrPSc protein to refold into a PrPC configuration.
e. People can acquire a prion-associated disease by eating beef from an animal infected with bovine spongiform encephalopathy (BSE).
d
51
Which statement about proteasomes is not correct?
a. Proteasomes found within the nucleus will degrade old, malfunctioning proteins.
b. Proteasomes degrade proteins that are tagged with a chain of ubiquitin proteins.
c. Proteasomes are found within the lumen of the endoplasmic reticulum.
d. The N-end rule is one factor that determines when a proteasome will target a particular protein.
e. Proteasomes unfold proteins before cutting them into pieces.
c
52
The position or the type of phospholipids found in a cell’s membrane can be altered by:
a. enzymatic modification of the head groups.
b. flippases.
c. phospholipid transfer proteins.
d. a and b
e. a, b, and c
e
53
Which protein facilitates the final step of fusion of a vesicle to a target membrane?
a. Rab proteins
b. clathrin
c. SNAREs
d. tethering proteins
e. none of the above
c
54
Which statement about lysosomes is not correct?
a. The pH inside an activated lysosome is below 7.
b. Lysosomes contain about 50 different hydrolytic enzymes.
c. The membrane of a lysosome has vATPase integral proteins.
d. Proteins destined for the lysosomes are tagged with phosphorylated mannose residues.
e. Proteins destined for the lysosomes leave the Golgi apparatus in COP-II coated vesicles.
e
55
A lysosomal storage disease ______________.
a. is caused by the absence of one type of hydrolytic enzyme within a lysosome
b. is characterized by the accumulation of an undigested compound within lysosomes
c. is caused by bacteria that inhibit fusion of the primary lysosome with an endocytotic vesicle
d. a and b
e. a, b, and c
d
56
Receptor-mediated endocytosis first produces ______ just inside the cell’s plasma membrane, which then coalesce (i.e. come together) to then form ______.
a. endosomes; late endosomes
b. endocytotic vesicles; early endosomes
c. endocytotic vesicles; lysosomes
d. clathrin-coated vesicles; lysosomes
e. early endosomes; endocytotic vesicles
b
57
What would happen to an Amoeba cell if it was treated with a drug that inhibited the salt pumps on the contractile vacuole’s membrane?
a. The contractile vacuole would fill normally and the cell would be able to expel excess water normally.
b. The contractile vacuole would fill too quickly with water and the cell would burst.
c. The contractile vacuole would fail to fill with water and the cell would burst.
d. The contractile vacuole would fill too quickly and the cell would shrink.
e. The contractile vacuole would fail to fill and the cell would shrink.
c
58
Water resorption by kidney cells can be increased by which process?
a. Opening of aquaporin channels on the cell’s outer plasma membrane.
b. Active transport of water through aquaporin channels on the cell’s outer plasma membrane.
c. Transport of vesicles carrying aquaporin channels to the cell’s outer plasma membrane.
d. Increasing fluidity of the plasma membrane by addition of more cholesterol.
e. Water resorption rates by kidney cells cannot be altered.
c
59
Acetylcholine binds to a sodium channel on a neural cell, opening the channel to allow sodium ions to flow quickly into the cell from a region of high sodium concentration to a region of low sodium concentration. This process is an example of _____________.
a. Ligand-gated facilitated diffusion
b. Repolarization
c. Mechanically-gated channel transport
d. Direct active transport
e. Voltage-gated active transport
a
60
A signal that is transmitted from one cell to its immediate neighbour is considered a(n) _____ signal.
a. autocrine
b. endocrine
c. paracrine
d. apocrine
e. exocrine
c
61
Which statement about cortisol hormone signaling is not correct?
a. Cortisol is hormone released by the adrenal glands during stress.
b. Cortisol is considered a hydrophobic signalling molecule.
c. Cortisol signalling does not require a receptor.
d. Cortisol induces cells to produce more glucose.
e. Cortisol promotes expression of the PEPCK gene, which encodes a protein involved in gluconeogenesis.
c
62
Which statement about GPCR signalling is correct?
a. A GPCR receptor binds to the beta (β) subunit of the G-protein.
b. The G-protein is composed of four subunits.
c. The alpha (α) subunit of the G-protein binds GTP after it binds to the effector protein adenylyl cyclase.
d. Hydrolysis of GTP causes the G-protein to detach from the effector adenylyl cyclase.
e. A GPCR can be deactivated by binding directly to clathrin, which induces the receptor to be drawn into the cell by endocyctosis.
d
63
Which statement(s) about receptor tyrosine kinases (RTKs) and/or GPCRs is/are correct?
a. A single RTK subunit has one transmembrane domain while GPCR proteins have seven.
b. The functional RTK receptor works as a dimer.
c. RTKs phosphorylate other proteins as part of the signal transduction process.
d. two of the above statements are correct.
e. a, b, and c are correct
e
64
Which second messenger molecule is initially responsible for preventing polyspermy?
a. calcium
b. cAMP
c. DAG
d. IP3
e. protein kinase C
a
65
A cell receives a signal to grow, and simultaneously receives another signal to resorb more glucose. The second signal causes the first signal to be temporarily ignored. This is an example of signal ______.
a. divergence
b. convergence
c. cross-talk
d. interconnection
e. restriction
c
66
The smooth endoplasmic reticulum is especially abundant in cells that synthesize considerable amounts of ______________.
a. toxins
b. proteins
c. enzymes
d. lipids
e. nucleic acids
d
67
The signal peptide of a newly-forming protein __________________.
a. is a stretch of positively charged amino acids
b. passes completely through the translocon and into the ER lumen before the rest of the newly translated protein passes through this channel
c. binds to the signal recognition particle
d. two of the above
e. a, b, and c
c
68
The protein disulphide isomerase found within the RER lumen ____________.
a. lacks a signal peptide sequence
b. synthesizes steroids
c. helps fold proteins
d. more than one of the above
e. none of the above
c
69
An integral protein ____________.
a. contains at least one transmembrane domain
b. might serve as a ion channel
c. may be glycosylated
d. two of the above
e. a, b, and c
e
70
The Golgi apparatus is involved in:
a. processing proteins that might end up on the cell’s outer membrane surface.
b. modifying proteins.
c. producing components of lysosomes.
d. two of the above
e. a, b, and c
e
71
Which type of glycosylations occur in the Golgi apparatus, but not the endoplasmic reticulum?
a. N-linked glycosylations
b. O-linked glycosylations
c. P-linked glycosylations
d. More than one of the above
e. None of the above
b
72
Which coat protein is involved in retrograde vesicle movements?
a. COP-I
b. COP-II
c. Clathrin
d. ARF1
e. More than one of the above.
a
73
Which of the following statements about the KDEL sequence is not correct?
a. The KDEL sequence is a stretch of amino acids that binds to an integral protein.
b. A protein with a KDEL sequence attaches to a KDEL receptor, which in turn, can interact with a coat protein.
c. The KDEL sequence helps proteins move in an anterograde direction through the endomembrane system.
d. The KDEL sequence can be found on BiP, a protein found in the endoplasmic reticulum.
e. The KDEL sequence is comprised of four amino acids.
c
74
Which statement about glycolipids and/or sphingolipids is not correct?
a. Accumulation of sphingolipids increases membrane fluidity.
b. Sphingolipids with sugar groups attached are called glycolipids.
c. Glycolipids play a role in electrical conduction of nerve cells.
d. Some viruses target glycolipids as a means of infecting cells.
e. Sphingolipids can play roles in cell-to-cell signaling.
a
75
Which of the following increases cell membrane fluidity at low temperatures?
a. Increasing the length of the fatty acid chains of the membrane phospholipids.
b. Increasing saturation of the fatty acid chains of the membrane phospholipids.
c. Increasing desaturase activity.
d. Decreasing the concentration of cholesterol within the membrane.
e. Increasing glycolipid concentration in the membrane.
c
76
Which of the following is typically the least abundant macromolecule within a cell’s plasma membrane?
a. Carbohydrates
b. Lipids
c. Proteins
d. Cholesterol
e. Water
a
77
Which ion transporter is considered the most important in terms of establishing the resting potential of electrically-sensitive cells (such as neurons and muscle cells)?
a. The v-ATPase
b. The H+/K+ ATPase
c. The Ca2+ pump
d. The Na+/K+ pump
e. The Na+/Ca2+ exchanger
d
78
______ transporters are most commonly associated with the development of resistance to chemotherapeutic drugs.
a. V-ATPase
b. ABC
c. P-type
d. glucose
e. none of the above
b
79
Which statement about the Na+/glucose cotransporter is true?
a. Inhibition of the Na+/glucose cotransporter can prevent severe water loss into the intestine during cholera infections.
b. The Na+/glucose cotransporter moves both molecules by diffusion.
c. The Na+/glucose cotransporter allows sodium to move down a concentration gradient while glucose moves against a concentration gradient.
d. Activity of the Na+/glucose cotransporter does not affect water movement across the cell’s membrane.
e. More than one of the above statements is true.
c
80
In cystic fibrosis patients, the ____ is defective in lung cells. The defect __________.
a. Na+/K+ pump ; increases water flow out of lung cells by osmosis
b. Cl- channel; reduces water flow out of lung cells by osmosis
c. Na+/K+ pump ; reduces water flow out of lung cells by osmosis
d. Cl- channel ; increases water flow out of lung cells by osmosis
e. Na+ channel ; increases water loss into the lungs by osmosis
b
81
Which of the following events can occur after glucagon binds its receptor on the cell’s surface?
a. Glycogen breakdown is increased.
b. Glycogen synthesis is inhibited.
c. Gluconeogenesis is induced by increasing expression of the PEPCK gene.
d. Two of the above can occur.
e. a, b, and c
e
82
Which of the following events does not occur when a cell needs to stop glucagon-induced signalling?
a. Phosphodiesterase activity increases.
b. Glycogen synthase is phosphorylated.
c. The GTP attached to a G-protein subunit is hydrolyzed.
d. Arrestin binds to the glucagon receptor.
e. The glucagon receptor is endocytosed.
b
83
Which of the following is not regulated by a GPCR?
a. Insulin-induced uptake of glucose in muscle cells.
b. Vasopressin-induced resorption of water by kidney cells.
c. Odorant reception by cells in the sinuses.
d. Acetylcholine-induced contraction of smooth muscle cells.
e. None of the above are GPCR-regulated.
a
84
If a cell is subjected to a heat stress, which of the following events may occur?
a. Various cellular proteins may unfold.
b. Heat shock proteins can bind to unfolded proteins and help refold them.
c. The cell may stop protein synthesis until the heat stress is over.
d. Two of the above statements are true.
e. a, b, and c
e
85
A protein destined to enter into the lumen of the rough endoplasmic reticulum:
a. possesses a hydrophobic signal peptide
b. possesses a positively charged signal peptide
c. is synthesized on a free ribosome within the cytoplasm, unfolded by chaperones, and then fed through a channel to enter the lumen of the RER
d. more than one of the above
e. none of the above
a
86
What proteins are involved in helping a vesicle from the ER recognize, attach (tether) to, and eventually fuse with the Golgi?
a. Rab proteins
b. SNARE proteins
c. Tethering proteins
d. All of the above
e. None of the above
d
87
All of the following are true about the endoplasmic reticulum (ER) except:
a. synthesis of detoxification enzymes in liver cells occurs in the smooth ER
b. proteins are glycosylated in the rough ER
c. the rough ER is the primary site of Ca2+ storage in muscle cells
d. lipid biosynthesis occurs in the smooth ER
e. integral proteins are synthesized by ribosomes on the rough ER
c
88
How and/or where do ribosomes attach to the rough endoplasmic reticulum (RER)?
a. Ribosomes attach to translocons found on the RER.
b. The attachment is assisted by the interaction of the signal recognition particle (SRP) binding to a receptor on the RER.
c. The ribosome binds to the RER, then binds the mRNA, and begins translation.
d. a and b
e. a, b, and c
d
89
What process is responsible for organelle turnover in the cell and carries out the regulated destruction of the cell's own organelles for the purpose of recycling the components of which they are made?
a. autolysis
b. phagocytosis
c. apoptosis
d. autophagy
e. heterophagy
d
90
A cell can respond quickly to an extracellular signal if _______.
a. the cell does not require a receptor for the signal molecule
b. the response does not require some of its proteins to be altered
c. the response does not require new gene transcription or protein synthesis
d. it is dead
e. it is bored
c
91
What feature of the lipid rafts may explain their thicker, gel-like state as compared to the surrounding more fluid membrane regions?
a. The fatty acid tails are more unsaturated.
b. The fatty acid tails are more saturated.
c. The fatty acid tails are longer.
d. a and c
e. b and c
e
92
The lipid composition on the endoplasmic reticulum’s membranes (including inner and outer sides of the membrane) can be altered by ________.
a. enzymes that change the polar head groups of the lipids
b. flippases
c. chaperone proteins
d. a and b
e. a, b, and c
d
93
Which of the following statements about mad cow disease is correct?
a. A person may suffer from damage to brain cells if s/he eats meat from a cow with this disease.
b. This disease is caused by a mis-folded prion protein.
c. The disease-associated form of the prion protein tends to aggregate into elongated fibers.
d. a and b
e. a, b, and c
e
94
A newly synthesized protein has two “start transfer” sequences and one “stop transfer” sequence. Which of the following statements about the protein is correct?
a. The mature protein will be found in the cytoplasm and not within the membrane.
b. The protein will have three transmembrane domains.
c. The protein is a peripheral membrane protein.
d. More than one of the above is true.
e. None of the above is true.
b
95
Which of the following statements about lysosomes is NOT correct?
a. Lysosomes can contain about 50 different types of hydrolytic enzymes.
b. Lysosomal membranes contain V-type pumps.
c. Lysosomal enzymes function optimally at pH 6.5-7.0.
d. Lysosomes help degrade worn out organelles.
e. Lysosomes that are missing a particular enzyme can become congested with certain macromolecules.
c
96
. After epinephrine binds to its GPCR on a smooth muscle cell, the G-protein activates phospholipase C to produce which second messenger molecules?
a. Inositol triphosphate (IP3)
b. Diacylglycerol (DAG)
c. cAMP
d. a and b
e. a, b, and c
d
97
. All of the statements about cholesterol are correct EXCEPT
a. Cholesterol can disrupt the close packing of fatty acid chains
b. At low temperatures, cholesterol prevents membranes from freezing by increasing fluidity
c. At high temperatures, cholesterol interacts with phospholipids to increase fluidity
d. Bacteria do not have cholesterol in their membranes
e. Cholesterol can comprise as much as 50% of some animal cell membranes.
c
98
. A(n) ________________ membrane protein may be found entirely outside the lipid bilayer on the extracellular surface, and can be associated with the membrane lipids’ polar heads by ___________ bonds.
a. integral; covalent
b. peripheral; noncovalent
c. lipid-anchored protein; noncovalent
d. peripheral; covalent
e. integral; noncovalent
b
99
Which statement is NOT correct about proteasomes?
a. The amino acid on the N-terminal of a protein can affect whether the protein is sent to the proteasome.
b. A protein with multiple ubiquitin proteins attached will be sent to the proteasome.
c. A mis-folded protein that cannot be folded properly will be sent to the proteasome.
d. When a protein is tagged with ubiquitin, the protein and the ubiquitin are degraded together.
e. The proteasome is a tube-like structure, comprised of four rings, with the central rings having a proteolytic function.
d
100
How does a freshwater protozoan fill its contractile vacuole with water?
a. Active transport is used to move salt ions into the vacuole, and water flows in by diffusion.
b. Active transport is used to pump water into the vacuole through aquaporins.
c. Diffusion of ions into the vacuole is followed by diffusion of water.
d. More than one of the above.
e. None of the above.
a
101
When glucagon binds to its receptor on a liver cell, which of the following is NOT involved in helping the cell release glucose?
a. Glycogen synthase is activated.
b. A transcription factor binds to the PEPCK gene promoter.
c. Protein kinase A (PKA) phosphorylates another kinase.
d. A G-protein subunit activates adenylyl cyclase.
e. cAMP activates PKA.
a
102
Which of the following oligosaccharide chains is/are assembled in both the ER and the Golgi complex (i.e. not just the ER, and not just the Golgi)?
a. O-linked oligosaccharides
b. N-linked oligosaccharides
c. glycogen
d. a and b
e. a, b and c
b
103
Which coated vesicles move materials in an anterograde direction from the ER to the Golgi complex?
a. COP-II -coated vesicles
b. COP-I -coated vesicles
c. Clathrin -coated vesicles
d. a and b
e. a and c
a
104
The KDEL sequence ____________.
a. is a stretch of amino acids that helps a protein be transported into the nucleus
b. allows a protein to move in a retrograde direction from the Golgi to the ER
c. of a protein binds directly to COP-I proteins, without any protein involved
d. binds to the signal recognition protein (SRP)
e. More than one of the above is correct.
b Correct response rate: 62%. The protein possessing the KDEL sequence does not bind directly to the COP-I protein; it binds to the KDEL receptor (and the receptor and coat protein are two separate proteins) The KDEL sequence is inside the ER lumen – the COP-I protein is on the other side of the membrane.
105
A cell uses receptor mediated endocytosis to acquire an extracellular nutrient. The nutrient will be found in a series of membrane-bound compartments, in the following sequential order:
a. clathrin-coated vesicle; late endosome; early endosome; lysosome
b. endocytotic vesicle; early endosome; late endosome; lysosome
c. early endosome; Golgi; late endosome; exocytotic vesicle
d. COP-I coated vesicle; early endosome; late endosome; lysosome
e. exocytotic vesicle; lysosome; early endosome; late endosome
b
106
. After a cell has produced enough glucose following glucagon stimulation, which of the following activities is NOT a step that will stop glucose production?
a. The cell will begin converting cAMP to AMP using phosphodiesterase.
b. Glycogen synthase is phosphorylated.
c. The GTP on the Gα subunit of the G-protein will be hydrolyzed into GDP.
d. G-protein receptor kinase (GRK or GPRK) phosphorylates the glucagon receptor.
e. The glucagon receptor is endocytosed.
b
107
. Which of the following statements about odorant reception is true?
a. Odorant receptors are Receptor Tyrosine Kinases (RTKs).
b. Dogs have fewer odorant receptors than humans.
c. cAMP is a secondary messenger molecule produced when an odorant binds to its receptor.
d. Dogs have fewer types of GPCRs in their noses than humans.
e. An odorant receptor can bind only one type of odorant molecule.
c
108
Which of the following statements about the sodium-potassium (Na+/K+) ATPase is NOT correct?
a. The Na+/K+ ATPase moves 3 sodium ions out of the cell for every 2 potassium ions it brings in.
b. The Na+/K+ ATPase is P-type pump.
c. The Na+/K+ ATPase uses indirect active transport to transport Na+ ions.
d. About a third of the cell’s energy is needed to drive the Na+/K+ ATPase.
e. A cell’s resting potential can be established by the Na+/K+ ATPase
c
109
Which of the following statements about calcium transport are correct?
a. High concentrations of calcium outside the cell can be maintained using a calcium-specific pump.
b. High concentrations of calcium can be found within the sarcoplasmic reticulum (ER) of some cells.
c. The cytoplasm of a resting muscle cell typically has a higher calcium concentration than the exterior of the cell.
d. a and b
e. None of the above are correct.
d
110
Which of the following transporters are most often associated with cancer cells developing an ability to tolerate chemotherapy agents?
a. Antiporters
b. Ligand-gated channels
c. V-type pumps
d. P-type pumps
e. ABC-type pumps
e
111
Which is not true about the response of cells to insulin?
a. Diets rich in fats and sugars can increase the risk of acquiring insulin receptor insensitivity.
b. Insulin binds to a RTK receptor that then transduces a signal to the cell to increase glucose uptake.
c. Glucose uptake by a cell occurs very soon after insulin reception because the cell begins to synthesize glucose transporters.
d. Type II diabetes can result from either a defective insulin receptor or a defective insulin-responsive signal transduction pathway within the cell.
e. Insulin insensitivity can be corrected in some diabetic mice by suppressing a protein tyrosine phosphatase (PTP) gene.
c
112
The activation of a common effector by a variety of different receptors is called _________.
a. divergence
b. convergence
c. crosstalk
d. transvergence
e. coherence
b
113
. _________ signaling occurs when a cell stimulates a neighbouring cell, whereas ______ signaling occurs when a cell stimulates itself.
a. Paracrine; endocrine
b. Paracrine; autocrine
c. Endocrine; synaptic
d. Autocrine; paracrine
e. Synaptic; paracrine
b
114
Which statement about cortisol (corticosteroid) signaling is NOT correct?
a. Cortisol activates transcription of the PEPCK gene to produce glucose.
b. Cortisol binds to a receptor on the cell’s surface.
c. Cortisol binds an intracellular protein that then acts as a transcription factor.
d. Cortisol is a hormone that stimulates targeted cells to produce glucose.
e. Cortisol is produced when an animal is stressed.
b
115
Which statements are true about second messenger molecules?
a. Second messenger molecules can amplify the intensity of a signal within a cell.
b. Second messenger molecules can help synchronize several cellular activities within a cell.
c. Cyclic AMP (cAMP) is a second messenger molecule stored within the ER.
d. a and b
e. a, b, and c
d
116
How does vasopressin affect the function or location of aquaporins?
a. It causes them to be targeted for destruction by proteasomes.
b. It causes vesicles carrying aquaporins to move to the cell’s surface.
c. It causes them to be removed from the membrane by endocytosis.
d. It causes them to be synthesized by the cell.
e. It causes them to be phosphorylated and opened.
b
117
Substance X is at higher concentration outside the cell than inside. A cell uses a channel to bring in substance X. The channel is opened when substance Y binds to it. This can be most accurately described as an example of ________.
a. passive transport
b. diffusion
c. ligand-gated facilitated diffusion
d. cotransport
e. indirect active transport
c
118
Which of the following statements is NOT correct about the endoplasmic reticulum (ER)?
a. The smooth ER (SER) is a site for calcium ion storage in cells.
b. N-glycosylation occurs in the rough ER (RER).
c. The RER is covered with ribosomes.
d. The RER is the primary site of synthesis of steroids.
e. The SER is a site of lipid biosynthesis.
d
119
Which type of macromolecule best describes the identity of the ABO antigens on the surface of red blood cells?
a. Glycolipids
b. Carbohydrates
c. Proteins
d. Glycoproteins
e. Lipids
a
120
What is the relevance of mannose-6-phosphate to lysosomes?
a. It is the sugar that lines the interior of a lysosome’s membrane.
b. It is a sugar added to proteins destined to be digested by the lysosomes.
c. It is a receptor for lysosomal lipids.
d. It is a sugar added to proteins that enables them to be transported into lysosomes.
e. It creates an acidic pH environment within the lysosomes.
d
121
Which of the following is/are true about a hydrophilic signaling molecule?
a. Its receptor is located in the cytoplasm of the target cell.
b. Once bound to its receptor, the receptor might bind another protein.
c. Once bound to its receptor, the receptor might dimerize and act as transcription factor.
d. More than one of the above
e. None of the above
b
Note: The most common incorrect answer was D, but only B is true. A is incorrect because a hydrophilic signaling molecule cannot pass through the membrane, so its receptor is embedded in the cell’s membrane. C is incorrect because a membrane bound protein cannot act as a transcription factor.
122
During the unfolded protein response, the cell can activate sensors that will direct the cell to:
a. increase transcription of genes that encode chaperone proteins.
b. stop or slow down translation of non-chaperone proteins.
c. begin cell division.
d. a and b
e. a, b, and c
d
123
Two signals, coming from two different receptors on the same cell, produce the same response in the cell. This is an example of:
a. signal crosstalk
b. signal divergence
c. signal convergence
d. signal transduction
e. signal cancelling
c
124
A molecular chaperone is a protein that:
a. helps newly synthesized proteins fold into the proper three dimensional structure.
b. helps heat denatured proteins refold back into their original shape.
c. can refold proteins in cells subjected to anoxia.
d. a and b
e. a, b, and c
e
125
The Golgi apparatus is involved in:
a. processing proteins that might end up on the cell’s outer membrane surface.
b. modifying proteins.
c. producing enzymes that will function in lysosomes.
d. two of the above
e. a, b, and c
d or e
Note: It seems that some people interpreted “producing enzymes” to mean “synthesizing enzymes”, and thought that the synthesis only occurs in the ER, with further modifications to the protein as not part of the synthesis process. While I would consider a modification part of the production process, I will concede that some people didn’t see it that way. I will therefore accept either D or E as correct.
126
A protein that needs to be moved from the Golgi back to the ER will have a _____ sequence. This protein will attach to a receptor that can recruit a _____ coat protein.
a. KKXX; COP-I
b. KDEL; COP-I
c. KKXX; COP-II
d. KDEL; KKXX
e. None of the above are correct
b
127
Scrapie and bovine spongiform encephalopathy (mad cow disease) are both:
a. characterized by neural malfunctioning and loss of muscle control.
b. caused by a misfolded protein.
c. caused by a form of protein that can aggregate into fibers.
d. Two of the above are correct.
e. Three of the above are correct.
e
Note: These diseases are caused by a normal prion protein that has folded improperly. The disease-causing protein (PrP-Sc) itself has the same amino acid sequence as its normal counterpart(PrP-C), but it has folded improperly, and causes other PrP-C to also misfold. These misfolded proteins then stick together to form fibers.
128
An amoeba fills its contractile vacuole with water by:
a. pumping ions into the vacuole, and the water follows by osmosis.
b. opening gated aquaporins on the vacuole’s membrane.
c. active transport of water.
d. removing ions from the vacuole, leaving the water behind.
e. pumping ions into the vacuole, allowing water to diffuse in, and then removing the salts from the vacuole by active transport before exocytosis of the water.
a
129
The position or the type of phospholipids found in a cell’s membrane can be altered by:
a. enzymatic modification of the polar head groups.
b. flippases.
c. phospholipid transfer proteins.
d. a and b
e. a, b, and c
e
130
A vesicle leaving the ER, heading to the Golgi, is initially covered with _______ proteins, but a GTPase known as _______ hydrolyzes GTP to GDP to cause the vesicle to lose its coat.
a. COP-II ; Sar1
b. COP-I ; Sar1
c. Clathrin ; Arf1
d. COP-I ; Arf1
e. COP-II ; Arf1
a
131
Which proteins facilitates the final step of fusion of a vesicle to a target membrane?
a. Rab proteins
b. clathrin proteins
c. SNAREs
d. tethering proteins
e. none of the above
c
132
Which of the following statements about lysosomes is NOT correct?
a. Lysosomes can contain about 50 different types of hydrolytic enzymes.
b. Lysosomal membranes contain V-type pumps.
c. Lysosomal enzymes function optimally at pH 8.0.
d. Lysosomes help degrade worn out organelles.
e. Lysosomes that are missing a particular enzyme can become congested with certain macromolecules.
c
Note: Lysosomes use V-type pumps to pump protons into the lysosome, thereby reducing the pH to around pH 5. pH 8.0 is considered basic.
133
Within the lumen of a vesicle are cargo proteins that are specifically meant to move from the ER to the Golgi. Which of the following describes proteins that bind directly to those specific cargo proteins?
a. They are receptor proteins
b. They are integral proteins
c. They are coat proteins
d. a and b
e. a, b, and c
d
134
Which of the following statements about the translocon is/are correct?
a. The translocon’s inner lining can bind a protein’s signal sequence.
b. A ribosome can be guided to the translocon by the signal recognition particle (SRP).
c. Translocons are found on the smooth endoplasmic reticulum (SER).
d. a and b
e. a, b and c
d
135
What is a stop transfer sequence?
a. It is a stretch of hydrophobic amino acids on an integral protein.
b. It is a cell surface receptor that controls endocytosis.
c. It is a group of carbohydrates on a protein.
d. It is a signal that sends a protein to the proteasome for destruction.
e. None of the above are correct.
a
136
A steroid hormone is an example of a ______ signal that binds to an ________receptor.
a. lipophobic ; intracellular
b. lipophobic ; intracellular
c. lipophilic ; intracellular
d. lipophilic ; extracellular
e. lipophobic ; extracellular
c
137
All of the statements about cholesterol are correct, except:
a. Cholesterol disrupts close packing of fatty acid chains.
b. At low temperatures, cholesterol prevents membranes from freezing by increasing fluidity.
c. At high temperatures, cholesterol interacts with phospholipids to increase fluidity.
d. Bacteria do not have cholesterol in their membranes.
e. Cholesterol can comprise as much as 50% of some animal cell membranes.
c
138
A GPCR is what type of protein?
a. A cytosolic protein
b. An integral protein
c. A peripheral protein
d. A lipid-anchored membrane protein
e. A nuclear protein
b
139
Vasopressin can induce kidney cells to collect water from urine. The collection of water is achieved by________________.
a. GPCR-induced movement of aquaporins to the kidney cells’ plasma membranes.
b. GPCR-induced opening of the voltage-gated aquaporin channels on the kidney cells.
c. aquaporin using active transport to move the water.
d. More than one of the above.
e. None of the above.
a
140
Glucose uptake from the intestinal lumen into the cells can involve the cotransport of sodium. Which of the following statements is true about this particular process?
a. Na+ and glucose diffuse into the cells by gated channels.
b. The Na+ and glucose enter the cells by P-type pumps.
c. An antiport pump moves the glucose into the cell while Na+ moves out.
d. This glucose uptake mechanism is an example of indirect active transport.
e. This glucose uptake mechanism can be inhibited by the cholera toxin.
d
Note: The sodium-glucose cotransporter uses indirect active transport to bring glucose into the cell (A is therefore incorrect). This pump is not a P-type pump – that term applies only to direct active transporters (hence B is incorrect). It is an example of symport (both ions move into the cell together), but the sodium is initially pumped out of the cell by the K+/Na+ ATPase (hence C is incorrect). This transporter is not affected by the cholera toxin – the toxin interferes with a G-protein that activates adenylyl cyclase (hence D is incorrect).
141
A cell uses receptor mediated endocytosis to acquire an extracellular nutrient. The endocytotic vesicle will next fuse with:
a. a clathrin-coated vesicle
b. the early endosome
c. the trans-Golgi network
d. the late endosome
e. a lysosome
b
142
Which of the following statements about ATPases is NOT correct?
a. P-type ATPases are all transmembrane proteins.
b. vATPases are involved in the pumping of protons into lysosomes.
c. Drug-resistant cancer cells can have increased numbers of P-type ATPases on the cell’s membrane.
d. P-type ATPases are phosphorylated following ATP hydrolysis.
e. ABC transporters have both an ATP-binding domain and a substrate-binding domain.
c
143
If an unfolded protein cannot be refolded correctly, it ___________.
a. is tagged with a single ubiquitin protein and sent to the proteasome.
b. is tagged with polyubiquitin and sent to the proteasome.
c. remains bound to a chaperone indefinitely.
d. will likely result in death of the cell.
e. is exocytosed out of the cell.
b
144
The hair cells within our ears respond to sound waves and send a signal to our brain by first using which type of channel or transporter?
a. Ligand-gated channel
b. Ion-gated channel
c. Voltage-gated channel
d. Mechanically-gated channel
e. None of the above
d
145
What feature(s) of the lipid rafts may explain their thicker, gel-like state as compared to the surrounding more fluid membrane regions?
a. The fatty acid tails are more unsaturated.
b. The fatty acid tails are more saturated.
c. The fatty acid tails are longer.
d. a and c
e. b and c
e
146
Which of the following statements about the sodium-potassium (Na+/K+) ATPase is NOT correct?
a. The Na+/K+ ATPase moves 3 sodium ions out of the cell for every 2 potassium ions it brings in.
b. The Na+/K+ ATPase is P-type pump.
c. The Na+/K+ ATPase uses indirect active transport to transport these two ions.
d. About a third of the cell’s energy is needed to drive the Na+/K+ ATPase.
e. A cell’s resting potential can be established by the Na+/K+ ATPase.
c
147
A GPCR signaling pathway needs to be shut down. Which of the following activities could be part of this process?
a. Phosphorylation of a G-protein
b. Clathrin-mediated endocytosis
c. Hydrolysis of GDP
d. Attachment of arrestin to the G-protein
e. Binding of the alpha subunit of the G-protein to adenylyl cyclase
b
Note: A is incorrect because the GPCR is phosphorylated, not the G-protein. C is incorrect because ATP is hydrolysed, not ADP. D is incorrect because arrestin binds the GPCR, not the G-protein. E is incorrect because binding of the alpha subunit to adenylyl cyclase continues to keep the signalling active.
148
Which of the following will not assist in the production or release of glucose into the blood from a liver cell?
a. Binding of glucagon to a GPCR on the cell’s surface.
b. Binding of cortisol to a transcription factor protein within the cell.
c. Dephosphorylation of glycogen synthase.
d. Binding of epinephrine to a GPCR on the cell’s surface.
e. Activation of protein kinase A (PKA).
c
149
Which of the following statements about odorant reception is true?
a. Odorant receptors are Receptor Tyrosine Kinases (RTKs).
b. Dogs have fewer odorant receptors than humans.
c. cAMP is a secondary messenger molecule produced when an odorant binds to its receptor.
d. Dogs have fewer types of GPCRs in their noses than humans.
e. An odorant receptor can bind only one type of odorant molecule.
c
150
Which second messenger molecule is initially responsible for preventing polyspermy?
a. cAMP
b. DAG
c. IP3
d. calcium
e. protein kinase C
d
151
In cystic fibrosis, the mucous within the lungs becomes thick and viscous because:
a. a defective chloride channel reduces water movement out of the lung cells.
b. too many sodium channels are at the lung cell surface, causing excess sodium secretion, followed by osmotic flow of water.
c. too many chloride channels allow the excessive flow of chloride out of the lung cell and into the mucous.
d. too much mucous is secreted from the lung cells
e. none of the above
a
152
Which statement about insulin signalling is true?
a. The insulin receptor is a GPCR.
b. After insulin binds to its receptor, the receptor becomes phosphorylated.
c. Type II diabetes is caused by an overly sensitive insulin receptor.
d. Insulin stimulates liver cells to release glucose into the bloodstream.
e. The functional insulin receptor is comprised of a single protein.
b
Note: The insulin is an RTK, not a GPCR. The receptor functions as a dimer, meaning it is comprised of two proteins, not one.
