• University of California, Davis

• BIS 104

Ch9 1. In the disease leukocyte adhesion deficiency, leukocytes cannot stop rolling at the site of a wound. Normally leukocytes are signaled through a ___________ pathway to activate ___________ to induce tight binding and eventually migration out of the vein.

A. GPCR; integrins

B. RTK; selectin

C. GPCR; ICAM

D. RTK; cytokine

E. GPCR; endothelial adhesion molecule

Ch 9 2. Antibody binding stimulates maturation of B-cells. Signaling occurs through a __________ and causes antibodies to be made without _____________.

A. GPCR; an IG domain

B. Tyrosine kinase; a trans-membrane span

C. GPCR; an Fc region

D. Tyrosine kinase; a Fab region

E. GPCR; a heavy chain

Ch 9 3. Will B-cell-mediated IgG secretion be effective against a Listeria infection?

A. Yes

B. No

1. Earl Sutherland performed a set of experiments discussed in the text. In brief, he

broke open liver cells, and separated soluble supernatant 1 from a membrane pellet.

Then he resuspended the membrane, added epinephrine, and spun again to get a

supernatant 2. He found that supernatant 2 plus supernatant 1 efficiently stimulated the

breakdown of glycogen. What essential signaling component was in Supernatant 1?

A. The β-adernergic receptor

B. Epinephrine

C. cAMP

D. Glycogen Phosphorylase Kinase

E. A stimulatory heterotrimeric G protein

2. Viagra induces blood flow by relaxing the smooth muscles surrounding blood vessels.

This is accomplished __________________.

A. by stimulating the nitric oxide transmembrane receptor which increases cAMP.

B. by blocking cGMP phospho diesterase.

C. by blocking the nitric oxide transmembrane receptor which activates tyrosine kinase

activity.

D. by inactivating guanylyl cyclase.

E. through IP3 signaling which blocks Ca++ release in muscles.

3. Grb2 is an important player we discussed in the EGF receptor pathway. You have been

given a cell line that does not express Grb2 and is therefore unable to respond to EGF.

What new protein could you engineer and express to make the cell able to respond and

up-regulate a signal in response to EGF?

A. Add a stretch of Prolines to Ras.

B. Add a GEF to the EGF receptor.

C. Add an SH3 domain to Ras.

D. Add an SH2 domain to SOS.

E. Add a GEF to SOS.

4. Which clathrin adaptor protein is involved in internalization of G-protein coupled

receptors?

A. Arrestin

B. GGA

C. BARK

D. AP2

E. triskelion

5-6. Using sequential differential centrifugation steps, you fractionate cellular organelles. You then run the fractions on an SDS-PAGE gel and detect your favorite proteins (A-E) by western analysis to determine which fraction they are in, resulting in the following results:

5. Which protein is most likely to be Raf?

A. Protein A

B. Protein B

C. Protein C

D. Protein D

E. Protein E

6. You closely examine the sequences of the proteins. Which protein is most likely to be a receptor tyrosine kinase?

A. Protein A

B. Protein B

C. Protein C

D. Protein D

E. Protein E

7. Cholera toxin and pertussis toxin both lead to abnormal levels of cell secretion of

fluids. Cholera toxin leads to diarrhea and dehydration. Pertussis toxin causes Whooping

cough. Choose the statement below that best describes the molecular mechanisms of

these two toxins.

A. both Cholera and Pertusis toxin leads to an increase of cAMP

B. Cholera toxin blocks inhibitory Gα, while Petrussis toxin blocks stimulatory Gα

C. Cholera toxin increases cAMP and pertussis toxin decreases cAMP

D. Cholera toxin blocks GEF activity of Gα, but Pertussis toxin blocks the GAP of a

different Gα

E. both Cholera and Pertussis toxin block the hydrolysis of GTP in Gα, leading to an

increase in cAMP

8. Different signaling pathways can converge on the same target. For example, both

acetylcholine and EGF both activate phospholipase C (PLC) proteins. PLC γ is activated

by EGF and PLC β is activated by acetylcholne. What does PLC γ have that PLC β lacks?

A. A GEF domain

B. A GAP domain

C. An SH3 domain

D. An SH2 domain

E. A Ras interaction domain

9. Over 30% of all cancers have mutations that over-activate Ras. These mutations

usually block the ________ activity of Ras. This causes Ras to interact with _______.

A. GTPase; Raf

B. GEF; Rab

C. kinase; Ran

D. GAP; MAPKK

E. GEF; Raf

10. In Cell Biology, we learned about the molecular mechanisms of many

pharmaceuticals. A third of all pharmaceuticals are targeted against which of the

following classes of proteins?

A. GPCR

B. RTK

C. Oncogenes

D. Channels

E. G-proteins

11. The thyroid stimulating hormone (TSH) stimulates the thyroid to secrete thyroid

hormone. A patient present in your office with a benign tumor on his thyroid that is

secreting large amounts of thyroid hormone, even without stimulation by TSH. You

sequence the gene encoding the TSH receptor from the tumor cells. It is a predicted

seven trans-membrane receptor. When the results come back from the DNA sequencing

lab, you’re stumped. You find point mutations in the third intracellular loop of the TSH

receptor. Luckily your intern has just earned an A in Cell Biology. She knows why the

patient’s thyroid is hyperactive. What does she propose?

A. The point mutation is causing a conformational change that makes the GEF of the

receptor constitutively active.

B. The point mutation is leading to a constitutive recruitment of an SH2 protein, leading

to a constitutive activation of the Ras/MAPK pathway.

C. The mutant TSH receptor is unable to bind TSH.

D. The point mutation is blocking the phosphorylation site of a G-protein receptor

kinase, blocking the internalization of the receptor.

E. The mutant TSH receptor is a receptor tyrosine kinase, and the point mutation

changes an important tyrosine.

2. A null mutation in the S. pombe gene wee1 will lead to __________ yeast because

___________.

A. Larger; cdc25 is inactivated

B. Smaller; T14 and Y15 remain unphosphorylated

C. Larger; T14 and Y15 are phosphorylated

D. Smaller; T161 is unphosphorylated

E. Smaller; T14 and Y15 are phosphorylated

2. You isolate a serine to alanine mutation in the C-terminus of the beta-adrenergic

receptor. You propose that this will lead to ______ failing to directly bind to the protein,

resulting in _______________.

A. BARK; a decrease in cAMP production.

B. G-alpha inhibitory; an increase in cAMP production.

C. G-alpha stimulatory; a decrease in cAMP production.

D. Clathrin; an increase in cAMP production.

E. Arrestin; an increase in cAMP production.

4. Which of the following pairs of antigens could be resolved using two antibodies and

an immunofluorescence microscope?

A. The SRP receptor in the GDP state and translocons

B. N-acetylglucosamine phsophotransferase and Arf1

C. Translocons and BiP

D. cis and trans Golgi of an animal cell

E. SRP in the GDP form and signal peptidase

5. In a mutant screen for genes that affect cell division, you isolate a cDNA and

determine its sequence. After analyzing the predicted amino acid sequence of the

protein you produce the above hydrophobicity plot. You predict that the protein is

_________ with Domain A _________.

A. a single pass membrane protein; outside the cell

B. a single pass membrane protein; in the cytoplasm

C. a double pass membrane protein; outside the cell

D. a double pass membrane protein; in the cytoplasm

E. a four pass membrane protein; in the membrane

6. This protein is likely a member of the _________ super family.

A. LDL receptor

B. Nuclear Hormone Receptor

C. NO receptor

D. Receptor Tyrosine Kinase

E. G-Protein Coupled Receptors

7. Closer analysis of the wild type amino acid sequence in domain A shows the following

amino acids: NPAY. However, in the mutant you isolated the predicted coding sequence

reveals a single amino acid change: APAY. Based on this mutation you predict this

protein will not be __________ and therefore fail to _________.

A. glycocylated; exit the ER

B. glycocylated; be internalized

C. incorporated into endocytotic vesicles; bind to adaptor proteins

D. phosphorylated; bind to SH2 domains

E. phosphorylated; bind to SH3 domains

8. You add a KDEL sequence to the C-terminus of this protein. Where would you now

find the bulk of this protein?

A. In the cytosol

B. In the membrane of the lysosome

C. In the plasma membrane

D. In the ER membrane

E. In the Golgi membrane

11. Which of the following pairs of antigens are far enough away so that they can be

resolved using a light microscope?

A. GPCR and PKA

B. The GEF for Ras and the EGF receptor

C. Adenylyl cyclase and β-adrenergic receptor

D. MAPK and transcription factors

E. Ras-GTP and Raf

13. You add a PKKKRKV to the middle of an otherwise normal BiP. Where would you now

predict the new protein to localize?

A. The ER

B. Secreted outside the cell

C. The Golgi

D. The nucleus

E. The cytoplasm

For questions 14-17: Midtermase is a soluble enzyme that is normally in the lysosomes of cells. The isolated acid hydrolase is a glycoprotein with a predicted molecular weight (just the protein) of 36 kD. It only has one asparagine in its sequence.

14. You mutate the single asparagine residue. Where would Midtermase now localize?

A. Lysosome

B. Cytosol

C. Secreted out of the cell

D. Trans-Golgi network

E. ER

The mRNA encoding midtermase was isolated and used in an in vitro translationtranslocation study. Five separate tubes were set up, each containing the mRNA for Midtermase, S35 Methionine, and all other ingredients necessary to achieve translation of the protein. The following reagents were added to the tubes:

Tube A: nothing else

Tube B: Salt-striped microsomes + protease Tube C: Microsomes + protease

Tube D: Microsomes + tunicamycin Tube E: Microsomes + GTP-γ-S

You were about to load an SDS-PAGE of each of the five samples, but dropped the unlabeled tubes! You randomly picked them up and loaded them into the gel. After detecting the radioactive bands in the SDS-PAGE gel, you saw the following pattern in the 5 lanes of the protein:

Questions 15-17: Which tube goes with which lane?

15. Which tube was loaded in lane 2? (Answer A through E)

Tube E

16. Which tube was loaded in lane 3? (Answer A through E)

Tube B

17. Which tube was loaded in lane 5? (Answer A through E)

Tube D

18. A Familial Hypercholesterolemia patient presents that is unable to internalize LDL

from the blood. Tests determine that she makes LDL receptors, but they are mutant. The

LDL receptors efficiently bind LDL on the plasma membrane, but are not observed in

coated pits. The mutation in the receptor is in ________.

A. The extracellular domain of the receptor.

B. The Clathrin binding domain.

C. The AP-2 binding domain.

D. The GGA binding domain.

E. A Tyrosine that is phosphorylated by a protein kinase.

20. Different signaling pathways can converge on the same target. For example, both

acetylcholine and EGF both activate phospholipase C (PLC) proteins. PLC γ is activated

by EGF and PLC β is activated by acetylcholine. What does PLC γ have that PLC β lacks?

A. A GAP domain

B. An SH3 domain

C. A GEF domain

D. An SH2 domain

E. A Ras interaction domain

21. Normally, the H+ proton ATPase pump is found in the lysosomal membrane. In the

cells from I-cell patients, the H+ ATPase pump fails to be _____ and is localized ____?

A. modified with sugar; in the lysosome

B. modified with phosphate; to the plasma membrane

C. modified with sugar; outside of the cell

D. translocated; in the cytosol

E. modified with phosphate; in the endoplasmic reticulum

23. In BIS 104, we learned about the molecular mechanisms of many pharmaceuticals.

A third of all pharmaceuticals are targeted against which of the following classes of

proteins?

A. Proto-Oncogenes

B. Tumor Supressors

C. G-proteins

D. GPCR

E. RTK

25. When you were a child, you were (hopefully) vaccinated for measles. You therefore

have ______ in your blood that will allow you to quickly respond to an exposure of

measles today by rapidly differentiating and secreting ________.

A. Memory B cells; IgG

B. Leukocytes; IgG and IgM

C. T cells; IgM

D. B cells; IgM

E. Plasma cells; IgG

28. In class we talked about the estrogen receptor. Which answer best describes the

estrogen receptor?

A. The estrogen receptor bind to estrogen in loops 2-3 of its extracellular domain

B. High activity of the estrogen receptor leads to an increase in uterine cancer

C. The estrogen receptor is a transcription factor.

D. Estrogen induces dimerization of the estrogen receptor

E. Tamoxifin induces activity of the estrogen receptor in breast tissue

30. Cholesterol in animal cells functions to _______________.

A. Stiffen the membrane and decrease the melting point

B. Fluidize the membrane and increase ion flow

C. Solubilize the membrane and decrease the melting point

D. Stiffen the membrane and increase the melting point

E. Stabilize the membrane and decrease ion flow

31. Pertusis toxin is produced by bacteria and leads to whooping cough. This infects 50

million people a year, killing over 350,000 world wide. It causes epithilal cells lining the

airways to secrete extra fluids. Like cholera toxin, pertusis toxin also leads to very high

levels of cAMP in the affected epithelial cells, but these two toxins work by different

mechanisms. What is the molecular mechanism of pertusis toxin?

A. It blocks GTPase activity of stimulatory Gα-protein

B. It binds to the ligand binding site of a GPCR, activating the GEF

C. It blocks GTPase activity of inhibitory Gα-protein

D. It locks stimulatory Gα-protein in the GDP form

E. It locks inhibitory Gα-protein in the GDP form

34. Antibody binding stimulates maturation of B-cells. Signaling occurs through a

__________ and causes antibodies to be made without _____________.

A. Tyrosine kinase; a Fab region

B. Tyrosine kinase; a trans-membrane span

C. GPCR; a Fc region

D. GPCR; a heavy chain

E. GPCR; an IgG domain

35. In patients with certain thyroid cancers, cells secrete thyroid hormone in the

absence of ligand for the thyroid stimulatory hormone receptor. Amino acid

substitutions in the third intracellular loop of the thyroid stimulatory hormone receptor

argue that this is caused by a dominant mutation that activates _______________ in the

absence of ligand.

A. wee1

B. IP3 receptors

C. Gα

D. PLCβ

E. cdc25

37. Defects in the gene CFTR are responsible for the disease Cystic fibrosis. The most

common mutation in CFTR is a deletion of F508. You examine the localization of the

F508 deletion mutant CFTR in the cell and find it accumulated in the ER and nowhere

else. Which of the following statements best explains your results.

A. The CFTR gene encodes a Cl- channel that normally localizes in the ER membrane.

The mutation blocks the Cl- channel from opening.

B. The CFTR protein is normally in the plasma membrane. The F508 mutation must

block the plasma membrane address peptide of the CFTR protein.

C. The CFTR protein is normally in the plasma membrane. The F508 mutation fails to

fold and is retained in the ER by the chaperone calnexin.

D. The CFTR protein is normally in the plasma membrane. The F508 mutation fails to

fold and is retained in the ER by trimming off all its glucoses.

E. The CFTR gene encodes a Na+ channel, and the mutation leads to high intracellular

levels of Na+.

40. You isolate a mutation that disrupts the activity of the Ran GAP. In such a cell you

notice that E2F is in the wrong cellular compartment. Why?

A. E2F can no longer bind Ran

B. Ran is stuck in the GDP form

C. β-importin is stuck to Ran

D. α-importin is stuck in the cytoplasm

E. β-importin is stuck in the nucleus

41-42. Using sequential differential centrifugation steps, you fractionate cellular organelles from a wild-type and mutant cell line. You then run the fractions on SDSPAGE and use antibodies against the C-terminus of your protein to identify which fractions your protein is in. Normally you find your favorite protein in the total cell lysate, the 600 xg supernatant and the 15,000 xg pellet. In the mutant cell line your favorite protein is still in the total cell lysate and the 600 xg supernatant, but is now instead in the 15,000 xg supernatant and the 100,000 xg supernatant. Also, you notice the mutant protein runs faster and further on the SDS-PAGE than the wild-type form.

41. You conclude which of the following about your protein?

A. The wild-type version is in the nucleus and the mutant version in the cytoplasm.

B. The wild-type version is in the ER or Golgi and the mutant form is secreted.

C. The wild-type version is in the mitochondria and the mutant in the nucleus.

D. The wild-type is in the lysosome and the mutant version is secreted from the cell.

E. The wild-type version is in the lysosome and the mutant version in the ER.

42. Why does the mutant version migrate much faster than the wild-type version? From

what you’ve learned in BIS104, propose the best hypothesis for what the mutation is in.

A. The mutation is in Clathrin.

B. The mutation is a point mutation changing a Serine to an Alanine.

C. The mutation knocks out the enzyme N-acetyl-glucosamine-phosphotransferase.

D. The mutation is a point mutation changing an Asparagine to an Alanine.

E. The mutation deletes the last four amino acids of the protein (KDEL).

43. Regulation of Raf by both the EGF receptor and the epinephrine receptor is an ex of

_________.

A. Convergence

B. IP3 signaling

C. G-protein regulation

D. Crosstalk

E. Convergence

49. You mutate a protein that normally has the following amino acids: P-N-Y-E-E-I-P.

However, in the mutant you isolated the predicted coding sequence reveals a single

amino acid change: P-N-A-E-E-I-P. Based on this mutation you predict this protein will not

be __________ and therefore fail to _________.

A. phosphorylated; bind to SH2 domains

B. phosphorylated; bind to SH3 domains

C. translocated; bind to SRP

D. ubiquitinated; be degraded

E. endocytozed; bind to adaptor proteins

50. Nitric Oxide (NO) induces blood flow by relaxing the smooth muscles __________.

A. by blocking cGMP phosphodiesterase.

B. by blocking the nitric oxide GPCR which activates guanylyl cyclase

C. by increasing cGMP by activating guanylyl cyclase.

D. through IP3 signaling which blocks Ca++ release in muscles.

E. by stimulating the nitric oxide GPCR which increases cAMP

For questions 52-53: You clone a cDNA encoding a possible transmembrane protein. The mRNA made from the cDNA is translated in vitro in the presence of 35S methionine and treated as indicated below

before being resolved by SDSPAGE and visualized by autoradiography

52. Assume there are no charged residues near

the first transmembrane domain. Where do you

expect the N-terminus of the protein to be

immediately after translation of the whole

protein.

A. Cleaved off the rest protein

B. Buried in the translocon

C. In the cytoplasm

D. In the ER lumen

E. In the hydrophobic part of lipid bi-layer

53. Which of the following best describes the

topology of the protein?

A. It crosses the membrane five times with its C

terminus outside the cell.

B. It crosses the membrane four times with its Cterminus outside the cell.

C. It crosses the membrane six with its C-terminus outside the cell.

D. It crosses the membrane five times with its C-terminus in the cytosol.

E. It crosses the membrane four times with its C-terminus in the cytosol.

54. You delete the first eight AND the last four amino acids of BiP. Where would you now

predict the majority of BiP to now localize?

A. Outside the cell

B. The Golgi

C. The nucleus

D. The ER

E. The cytoplasm

57. If you wanted to target a normally cytoplasmic protein to be secreted outside the

cell, what would you add to it?

A. NPXY

B. KDEL

C. PNYEEIP

D. KKKRK

E. FVIILFVL

58. Assume this is a plasma membrane protein. Where are the N and C terminal ends of

the protein?

A. The N-terminus is in the cytoplasm and the C-terminus outside of the cell

B. Both are inside the cell

C. Both are outside the cell

D. The N-terminus is outside of the cell and the C-terminus in the cytoplasm

E. The N-terminus is imbedded in the lipid bi-layer and the C-terminus is outside the cell

59. In the rigor state, a motor is attached to a cytoskeletal element. Compare and

contrast the rigor state of Myosin II to conventional kinesin-1.

A. Myosin is in rigor when no nucleotide is present and kinesin is in rigor when

nonhydrolyzable ATP is present.

B. Myosin is in rigor with non-hydrolyzable ATP is present and kinesin is in rigor with no

nucleotide.

C. Myosin is in rigor with non-hydrolyzable ATP is present and kinesin is in rigor with

non-hydrolyzable GTP.

D. Myosin is in rigor when no nucleotide is present and kinesin is in rigor when

nonhydrolyzable GTP is in the tubulin.

E. Both Myosin and kinesin are in rigor when no nucleotide is present.

61-62. Using sequential differential centrifugation steps, you fractionate cellular organelles. You then run the fractions on an SDS-PAGE gel and detect your favorite

proteins (A-E) by western analysis to determine which fraction they are in, resulting in the following results:

61. Which protein is most likely to be Adenylyl

cyclase?

A. Protein A

B. Protein B

C. Protein C

D. Protein D

E. Protein E

62. Which protein is most likely to be the

estrogen receptor in the presence of estrogen?

A. Protein A

B. Protein B

C. Protein C

D. Protein D

E. Protein E

63. When the rapid DNA damage checkpoint is activated in G2, which of the following

occurs?

A. Chk1 is in the non phosphorylated form

B. Wee1 activity is activated by chk1

C. Cdc25 is removing phosphates from CDK

D. Cdc25 is removing phosphates from cyclinB

E. Cdc25 is in the cytoplasm

66. SOS is an important player we discussed in the EGF receptor pathway. You have

been given a cell line that does not express SOS and is therefore unable to respond to

EGF. What new protein could you engineer and express to make the cell able to

respond and up-regulate a signal in response to EGF?

A. Add an SH3 domain to Ras.

B. Add an SH2 domain to a Ras GEF.

C. Permanently attach Ras to the membrane.

D. Add a stretch of Prolines to Ras.

E. Add a GEF to the EGF receptor.

5. cAMP is an important second messenger we learned about. What does cAMP do?

A. cAMP induces a G-alpha protein

B. cAMP inhibits the regulatory subunit of protein kinase A

C. cAMP induces the intracellular levels of Ca++

D. cAMP activates phospholipase C

E. cAMP activates protein kinase C

8. Arf1 is the G protein for COP I vesicles that acts analogously to Sar1 for COP II

vesicles. Where would you expect to find the GEF for Arf1?

A. The cis-Golgi membrane

B. On COP II vesicles

C. The cytoplasm

D. Associated with COP I components

E. The ER membrane

Questions 11-13: A culture of cells was first treated with nocodazole (which antagonizes microtubule formation and hence arrests cells at the beginning of mitosis) for 24 hours to synchronize the cell population. The nocodazole was then removed from the cell culture and the culture was then continuously incubated with H3- thymidine for the next 48 hours. The amount of incorporation of H3- thymidine into the cells was plotted as a function of time after the start of incubation with H3-thymidine. Assume M-phase is less than 1 hour. These results are shown in the figure right.

11. How long is the cell cycle of this cell type?

A. 5 hours

B. 10 hours

C. 20 hours

D. 25 hours

E. 35 hours

12. How long is S-phase in this cell type?

A. 1 hour

B. 5 hours

C. 8 hours

D. 15 hours

E. 25 hours

13. How long is G1 in this cell type?

A. 1 hour

B. 5 hours

C. 10 hours

D. 15 hours

E. 20 hours

14. BiP is normally a component of the ER lumen. You add a PKKKRKV to the middle of

an otherwise normal BiP. Where would you now predict the new protein to localize?

A. The ER

B. Secreted outside the cell

C. The Golgi

D. The nucleus

E. The lysosome

15. You remove a KKVI sequence from the C-terminus of the KDEL receptor. Where

would you now find the majority of BiP?

A. Outside the cell

B. The ER

C. The cytoplasm

D. The Golgi

E. The lysosome

17. You isolate a loss-of function mutation in a bacterial gene that codes for a enzyme

that normally de-saturates fatty acids. What effect on the properties of the membrane

would you expect such a mutation to have?

A. An increase in the number of carbon double bonds and an increase in membrane

fluidity.

B. An increase in the number of carbon double bonds and a decrease in membrane

fluidity.

C. A decrease in the number of carbon double bonds and an increase in membrane

fluidity.

D. A decrease in the number of carbon double bonds and a decrease in membrane

fluidity.

E. An increase in the number of carbon double bonds and an increase in the levels of

cholesterol.

18. Which statement BEST describes the role of metalloproteases in cancer progression.

A. Metalloproteases induce cell growth and division and act as oncogenes.

B. Metalloproteases block metastasis, and therefore act as tumor suppresors.

C. Metalloproteases degrade growth factors and therefore act a tumor suppressors.

D. Metalloproteases play a role in apoptosis (programmed cell death).

E. Metalloproteases help recruit blood vessels to the tumor.

For questions 19-21: You clone a cDNA encoding a possible transmembrane protein. The mRNA made from the cDNA is translated in vitro in the presence of S 35 methionine and treated as indicated below before being resolved by SDS-PAGE and visualized by autoradiography.

19. Why is the protein in lane 3 smaller than the one in

lane 1?

A. The protein in lane 3 is cytoplasmic

B. The protein in lane 3 fails to be translocated into

microsomes

C. The protein in lane 1 has been N-linked glycosylated

D. The protein in lane 3 is missing its signal peptide and is

not glycosylated

E. The protein in lane 3 is unfolded

20. Which of the following best describes the topology of the protein?

A. It crosses the membrane three times with its N-terminus in the cytosol

B. It crosses the membrane five times with its C-terminus in the ER lumen.

C. It crosses the membrane four times with its N-terminus in the ER lumen.

D. It crosses the membrane three with its N-terminus in the cytosol.

E. It crosses the membrane three with its N-terminus in the ER lumen.

21. Why is there no protein in the last lane (lane 6)?

A. Lane 6 is missing signal peptidase

B. In lane 6, the translocon is always open

C. Lane 6 is missing SRP receptor

D. Lane 6 is missing SRP

E. In lane 6, the microsomes are permeable to the protease

27. Adding ARP2/3 to the A part of the graph, will ______ of actin filaments by ______.

A. enhance growth; by lowering the critical concentration

B. shorten phase A; enhancing nucleation

C. enhance nucleation; sequestering G-actin

D. prevent growth; sequestering F-actin

E. prevent nucleation; blocking ActA

29. You isolate a mutation in which Ran is stuck in a GDP-bound form. In such a cell you

notice that a GFP with a nuclear localization signal (NLS) that normally is targeted to the

nucleus is no longer seen in the nucleus. Why?

A. β-importin is sequestered by Ran

B. α-importin is stuck in the cytoplasm

C. β-importin is stuck in the nucleus

D. The NLS-GFP can no longer bind Ran

E. You need GTP hydrolysis to see GFP fluorescence

33. Nitroglycerin, which produces NO, induces blood flow by relaxing the smooth

muscles surrounding blood vessels. This is accomplished __________________.

A. by stimulating the nitric oxide transmembrane receptor which increases cGMP.

B. by blocking cGMP phospho diesterase.

C. by increasing cGMP by activating guanylyl cyclase.

D. through IP3 signaling which blocks Ca++ release in muscles.

E. by blocking the nitric oxide transmembrane receptor which activates gunylyl cyclase

34. If you wanted to target a normally cytoplasmic protein to be secreted outside the

cell, what would you add to it?

A. KDEL

B. LVIFILFV

C. PNYEEIP

D. KKKRK

E. NPXY

35. Earl Sutherland performed a set of experiments we discussed in class. In brief, he

broke open liver cells, and separated soluble supernatant 1 from a membrane pellet.

Then he resuspended the membrane, added epinephrine, and spun again to get a

supernatant 2. He found that supernatant 2 plus supernatant 1 efficiently stimulated the

breakdown of glycogen. What essential signaling component was in Supernatant 2?

A. The β-adernergic receptor

B. Epinephrine

C. cAMP

D. Glycogen Phosphorylase Kinase

E. A stimulatory heterotrimeric G protein

36. We discussed amplification in the fight or flight pathway. How many molecules of

glucose are secreted in response to one molecule of epinephrine?

A. 10

B. 100

C. 1,000

D. 100,000

E. 100,000,000

37. Retrograde traffic from the cis golgi to the ER is important to keep ER proteins in the ER. Type 1 transmembrane proteins targeted to the ER have a _______ signal and return to the ER in ________ coated vesicles.

A. KKXK; COPII

B. KDEL; COPI

C. PKKKRKV; COPII

D. KKXK; COPI

E. KDEL; COPII

38. SOS is an important player we discussed in the EGF receptor pathway. You have

been given a cell line that does not express SOS and is therefore unable to respond to

EGF. What new protein could you engineer and express to make the cell able to respond

and up-regulate a signal in response to EGF?

A. Add an SH2 domain to a Ras GEF.

B. Add a GEF to an SH3 protein.

C. Add a stretch of Prolines to Ras.

D. Add a GEF to the EGF receptor.

E. Add an SH3 domain to Ras.

42. Kinesin is used for many different things in the cell. Which of the following is NOT a

role for a kinesin?

A. Movement of flagellum

B. Movement of chromosomes in prometaphase

C. Keeping the spindle poles apart in mitosis

D. Transport of neurotransmitters down the axon towards the synapse

E. Vesicle trafficking from the Golgi to the ER

44. Of the different types of clathrin adaptor proteins we discussed in class, which one is

involved in internalization LDL receptors?

A. Arrestin

B. GGA

C. BARK

D. AP2

E. triskelion

45. You add a KDEL sequence to the C-terminus of Grb2. Where would you now find

Grb2?

A. In the Golgi

B. In the nucleus

C. In the ECM

D. In the ER

E. In the cytoplasm

46. What is the key player in the astral repulsion force?

A. Dynein at the centrosome

B. Actin-myosin contraction

C. Kinesin-13

D. Chromokinesin

E. Bi-polar kinesin-5

47. A mutation in Ras locks it in a GTP form. This mutant form of Ras acts as ______.

A. a proto-oncogene

B. an oncogene

C. a tumor suppressor

D. a GEF for Raf

E. a kinase for Raf

48. You isolate a secretion defective mutant strain in yeast that has a very large ER and

no ER derived vesicles. A mutation disrupting which of the following proteins could lead

to such a phenotype?

A. The G protein ARF1 stuck in the GDP form

B. A t-SNARE in the ER membrane

C. A COPI complex component

D. The GEF protein Sec12

E. The GAP protein in COPII complex

49. The rare lysosomal storage disease I-cell disease was used to discover the

mechanism of lysosomal targeting of acid hydrolases. In these patients lysosomal

enzymes are secreted into the blood, and the lysosome becomes bloated with

undegraded material. Which of the following proteins would you hypothesize is deficient

in I-cell disease patients?

A. Clathrin

B. Glucosidase

C. Dynamin

D. NAG-phosphotransferase

E. Calnexin

52. Listeria monocytogenes recruits actin from the host cell to create an actin tail used

to move around in the cell. What is the protein encoded by the bacteria that is used to

polymerize actin?

A. Act A

B. WASP

C. ARP2/3

D. CapZ

E. profilin

53. Which protein is most likely to cross the membrane seven times?

A. Protein A

B. Protein B

C. Protein C

D. Protein D

E. Protein E

54. Which protein is most likely to be marked with a manose-6-phosphate?

A. Protein A

B. Protein B

C. Protein C

D. Protein D

E. Protein E

55. Which protein is most likely to have a PKKKRKV

sequence?

A. Protein A

B. Protein B

C. Protein C

D. Protein D

E. Protein E

5. Which protein is most likely to be the β-adrenergic

receptor?

A. Protein A

B. Protein B

C. Protein C

D. Protein D

E. Protein E

6. Which protein is most likely to be PKA?

A. Protein A

B. Protein B

C. Protein C

D. Protein D

E. Protein E

7. Which protein is most likely to be E2F?

A. Protein A

B. Protein B

C. Protein C

D. Protein D

E. Protein E

57. The mRNA for a secreted protein is isolated and placed in a test tube in the presence of reticulocyte lysate (all the substances required for in vitro protein synthesis). The protein is then produced in the presence or absence of microsomes. The protein produced in the presence of microsomes is slightly smaller than the protein produced in the absence of microsomes. What is different about these two proteins?

A. The protein produced without microsomes has a signal patch.

B. The protein produced with microsomes is a trans-membrane protein.

C. The protein produced without microsomes has a secretory signal.

D. The protein produced with microsomes contains a secretory signal.

E. The protein produced without microsomes has an extra 10 hydrophobic amino acids

at its C-terminus.

59. Microtubules undergo dynamic instability, and proteins regulate the switches

between growing and shrinking. Which of the following is a true statement?

A. MAP2 prevents catastrophes and kinesin-13 prevents rescues.

B. MAP2 and kinesin-14 regulate how microtubules attached to the kinetochore undergo

flux.

C. MAP2 increases the rate of rescues, and Kinesin-13 increases the rate of

catastrophes.

D. Kinesin-13 induces catastrophes, while kinesin-14 prevents catastrophes.

E. Tau stabilizes microtubules, while MAP2 destabilizes them.

60. What is the key player in pushing the spindle poles apart?

A. Kinesin-13

B. Kinesin-14

C. Chromokinesin

D. Kinesin-5

E. Dynein at the kinetochore

3. Signal pathways crosstalk to one another. One example is that _______ activates Raf,

but _______ inactivates Raf.

A. Ras GTP; PKA

B. Ras GDP; phospholipase C

C. EGF; PLC

D. MAPK; a GAP for Ras

E. cAMP; SOS

4. Different signaling pathways can converge on the same target. For example,

acetylcholine activates ______________, while EGF activates _______________.

A. Phospholipase C γ (that has an SH2 domain); Phospholipase C β (that is activated by a

Gα)

B. Phospholipase C γ (that has an GEF domain); Phospholipase C β (that is activated by a

Gβγ)

C. Phospholipase C β (that is activated by a Gα); Phospholipase C γ (that has an SH2

domain)

D. Phospholipase C γ (that is activated by a Gα); Phospholipase C β (that has an SH2

domain)

E. Phospholipase C γ (that has an Ras GEF domain); Phospholipase C β (that is activated

by IP3)

8. Which of the following cellular signals displays the highest level of amplification?

A. Estrogen

B. Epinephrine

C. IP3

D. EGF

E. Nitric Oxide

9. In the disease leukocyte adhesion deficiency, leukocytes can not stop rolling at the

site of a wound. Normally leukocytes are signaled through a ___________ pathway to

activate ___________ on the leukocyte to induce tight binding and eventually migration

out of the vein.

A. GPCR; ICAM

B. RTK; cytokine

C. GPCR; endothelial adhesion molecule

D. GPCR; integrins

E. RTK; selectin

12. Microtubules undergo dynamic instability, and proteins regulate the switches

between growing and shrinking. Which of the following is a true statement?

A. MAP2 increases the rate of rescues, and Kinesin-13 increases the rate of

catastrophes.

B. Kinesin-13 induces catastrophes, while kinesin-14 prevents catastrophes.

C. Tau stabilizes microtubules, while MAP2 destabilizes them.

D. MAP2 prevents catastrophes and kinesin-13 prevents rescues.

E. MAP2 and kinesin-14 regulate how microtubules attached to the kinetochore undergo

flux

19. An infant, that is unable to acquire antibodies properly from his mother's breast

milk, is born. Tests determine that he makes receptors for the antibodies, but they are

mutant, containing a tyrosine to cystine mutation. The antibody receptors efficiently

bind the antibodies on the plasma membrane, but are not observed in coated pits. The

mutation in the receptor is in ________.

A. The signal peptidase recognition sequence.

B. The Clathrin binding domain.

C. The domain that binds to the mother’s antibodies.

D. The AP-2 binding domain.

E. The GAP activity domain.

22. Dynein is used for many different things in the cell. Which of the following is NOT a

role for dynein?

A. Movement of cilia

B. Movement of kinetochores in prometaphase towards the centrosome

C. Keeping the spindle poles apart in mitosis by pulling on them from the cortex

D. Transport of vesicles in the axon towards the cell body

E. Vesicle trafficking from the Golgi to the ER

24. Which of the following statements best describes the role of Protein A?

A. Protein A is an important reagent in western blotting

B. Protein A is an important component for translocation

C. Protein A is an important reagent for immunoprecipitations

D. Protein A comes from Listeria

E. Protein A binds the Fab region

53. Defects in the gene CFTR are responsible for the disease Cystic fibrosis. The most

common mutation in CFTR is a deletion of F508. This mutation results in the addition of

glucose to the CFTR protein and its binding to ________. Normally the CFTR protein

localizes to the plasma membrane. The mutant CFTR protein ends up ___________.

A. calnexin; in the cytosol for degredation

B. BiP; secreted outside the cell

C. Calnexin; in the plasma membrane

D. KDEL receptor; in the ER

E. BiP; the lysosome for degradation

11. BiP is normally a component of the ER lumen. You add a "stop transfer" signal of

about 20 hydrophobic amino acids to the middle of the BiP protein sequence. Where

would you now predict the bulk of BiP to localize?

A. The ER lumen

B. The ER membrane

C. The plasma membrane

D. The nuclear envelope

E. Secreted outside the cell

D. Protein A comes from Listeria

E. Protein A binds the Fab region

53. Defects in the gene CFTR are responsible for the disease Cystic fibrosis. The most

common mutation in CFTR is a deletion of F508. This mutation results in the addition of

glucose to the CFTR protein and its binding to ________. Normally the CFTR protein

localizes to the plasma membrane. The mutant CFTR protein ends up ___________.

A. calnexin; in the cytosol for degredation

B. BiP; secreted outside the cell

C. Calnexin; in the plasma membrane

D. KDEL receptor; in the ER

E. BiP; the lysosome for degradation

11. BiP is normally a component of the ER lumen. You add a "stop transfer" signal of

about 20 hydrophobic amino acids to the middle of the BiP protein sequence. Where

would you now predict the bulk of BiP to localize?

A. The ER lumen

B. The ER membrane

C. The plasma membrane

D. The nuclear envelope

E. Secreted outside the cell