Cell Bio 1St Exam

Front 1

What specific primordial cellular functions is the Szostak lab currently trying to recreate in their "protocells"?

Back 1

A. The generation of mitochondria

B. The conversion of an RNA genome to a DNA genome

C. Efficient and high fidelity RNA-dependent RNA replication

D. Efficient and high fidelity RNA-dependent protein synthesis

E. The formation of a nucleus

Hint 1

C

Front 2

The switch from unicellular organisms to multi-cellular ones:

Back 2

A. Requires a significant increase in the number of genes that encode proteins

B. Evolved independently multiple times

C. May have originated with a single amino acid change in a single protein to enable cells to remain attached after completing cell division

D. A and B and C

E. B and C

Hint 2

E

Front 3

Mesophiles are:

Back 3

A. Prokaryotic Eubacteria

B. Prokaryotic Archea

C. Eukaryotic Eubacteria

D. Eukaryotic Archea

E. Eubacterial Archea

Hint 3

A

Front 4

Which are the following is/are applicable only to eukaryotes and not prokaryotes?

Back 4

A. B and D and F

B. DNA genome

C. B and D

D. Multiple compartments

E. D and F

F. Multicellular

G. B and F

Hint 4

E

Front 5

Which of the following observations is/are most consistent with the origin of mitochondria?

Back 5

A. 80-90% of all mitochondrial proteins are derived by a combination of horizontal gene transfer between other eukaryotes; additional endosymbiotic events involving non-alpha-proteobacterial prokaryotes; and other unknown origins

B.10-20% of all mitochondria proteins trace their ancestry bask to an original alpha-proteobacterial endosymbiont.

C. A and B

D. Mitochondria RNA polymerases and ribosomes more closely resembles those found in eukaryotes than in prokaryotes

E. All of the above

Hint 5

C

Front 6

What proportion of the protein-encoding genes identified in the sequenced genomes of several model organisms has been functionally characterized?

Back 6

A. 100%

B. 75%

C. 50%

D. 25%

E. 10%

Hint 6

C

Front 7

Kachroo et al, reported efforts to systematically replace 414 essential yeast genes with their human orthologs. Based on their findings, which statement most accurately summarizes which yeast genes can be successfully “humanized” thereby demonstrating their evolutionary conservation?

Back 7

A. All essential yeast genes can be successfully humanized irrespective of their functions.

B. Nearly half of all essential yeast genes can be successfully humanized irrespective of their functions.

C. Nearly half of all essential yeast genes can be successfully humanized, but genes involved in metabolism are significantly more replaceable than genes involved in DNA replication/repair and cell growth and death.

D. Nearly half of all essential yeast genes can be successfully humanized, but genes involved in DNA replication/repair and cell growth and death are significantly more replaceable than genes involved in metabolism.

E. No essential yeast genes can be successfully humanized, but half of all nonessential yeast genes can be successfully humanized irrespective of their functions.

Hint 7

C

Front 8

Which of the following is the predominant storage form of fatty acids in mammalian cells?

Back 8

A. Phosphoglycerides

B. Sterols

C. Phopholipids

D. Triacylglycerides

E. "free" unesterified fatty acids

Hint 8

D

Front 9

Some typical fatty acids are: myristic, CH3(CH2)12COOH; stearic; CH3(CH2)16COOH; lignoceric, CH3(CH2)22COOH; linoleic, CH3(CH2)4CH=CHCH2CH=CH(CH2)7COOH; palmitic CH3(CH2)14COOH; and hexadecatrienoic, CH3(CH2)8CH=CH-CH=CH-CH=CH-COOH. Use this information to answer the following question: The plasma membranes of cancerous liver cells (hepatoma cells) have greater fluidity than normal liver cells even when both cell types are grown at 37°C. Which two fatty acids would be more abundant in the plasma membranes of the hepatoma cells relative to normal liver cells to account for their increased fluidity when both cell types are grown at 37°C.

Back 9

A. Lignoceric and Stearic

B. Lignoceric and Myristic

C. Lignoceric and Linoleic

D. Myristic and Stearic

E. Myristic and Linoleic

Hint 9

E

Front 10

Which of the following could potentially form a membrane spanning amphipathic alpha-helix?

Back 10

A. ALVIVLLIVLLVFLILGVFLL

B. ALVIVLLIVLPVFLILGVFLL

C. ALSTVLNTVLDQFLRSGVENL

D. ALSTVLNTVPDQFLRSGVENL

E. NRSTDENTQKDQTRRSEDENR

Hint 10

C

Front 11

Here's another opportunity to get used to determining structural features of a polypeptide based on its amino acid sequence. As we’ll discuss later in the course, short amino acid sequences can be used as “epitope tags”. Recombinant DNA technology is used to incorporate one or more of these amino acid sequences into a protein of interest. This enables the “tagged” protein to be detected and even purified using a highly specific and commercially available antibody directed against the epitope tag. The amino acid sequences for three of the most commonly used epitope tags are: Myc tag: ASMQKLISEEDL Flag tag: DYKDDDDK HA tag: YPYDVPDYA Which of the following accurately pertains to the amino acid sequences of all 3 tags?

Back 11

A. Each of the 3 tags could readily form an α-helix.

B. Each of the 3 tags contains at least one aromatic amino acid.

C. Each of the 3 tags has an overall net negative charge at neutral pH.

D. Each of the 3 tags contains at least one positively charged amino acid at neutral pH.

E. Each of the 3 tags lacks an amino acid with a free hydroxyl group

Hint 11

C

Front 12

Which one of the following cannot be transported into a typical mammalian cell by facilitated transport even though its transport might be thermo favored?

Back 12

A. Ca2+

B. Fe3+

C. Na+

D. H20

E. C6H12O6

Hint 12

B

Front 13

What do uniporters and ion channels have in common?

Back 13

A. Both are gated

B. Both facilitate transport of molecules against concentration gradients

C. Both facilitate transport of molecules down concentration gradients

D. Both transport molecules at comparable rates.

E. Both undergo transformations between inward-facing and outward-facing conformations during each transport cycle

Hint 13

C

Front 14

What specifically defines a co-transporter as an antiporter?

Back 14

A. Both molecules are imported into the cell.

B. Both molecules are exported out of the cell.

C. Both molecules move down their concentration gradients. D. One molecule is transported against its concentration gradient & the other is transported down its concentration gradient.

E. One molecule is imported and the other molecule is exported.

Hint 14

E

Front 15

True or false: Transport directed by uniporters is reversible and the direction of transport will change if the direction of concentration gradient changes

Back 15

True

Front 16

The figure below depicts the glucose binding site for GLUT1. You’ve purified & determined the amino acid sequence of the glucose binding site for the GLUTZ transporter in which Gln282 is replaced by N; Glu283 is replaced by D; and Thr310 is replaced by S. Based solely on this information, what can you most likely predict about GLUTZ’s ability to transport glucose relative to GLUT1?

https://collab.itc.virginia.edu/access/content/attachment/d92f63b2-7cdb-4381-a8a2-5f99559813a0/Tests%20_%20Quizzes/339b582a-2590-494d-9bec-803ff3ece545/GLUT1.pdf

Back 16

A. Km for GLUTZ is most likely to be greater than the Km for GLUT1.

B. Km for GLUTZ is most likely to be less than the Km for GLUT1.

C. Km for GLUTZ is most likely to be nearly the same as the Km for GLUT1.

D. Can’t predict anything about the Km for GLUTZ relative to GLUT1.

E. The amino acids comprising the glucose binding site determine Vmax, not Km.

Hint 16

C

Front 17

[Ca2+] within the endoplasmic reticulum (ER) is 10–3M. Cytosolic [Ca2+] is 10–7M. Plant vacuoles are functionally equivalent to the lysosomes in animal cells & have an internal pH of 3.0. Cytosolic pH of a typical plant cell is 7.0. Which transport reaction has a higher (more positive) ΔGc, H+ import into vacuoles or Ca2+ import into the ER & why?

Back 17

A. H+ import into the vacuole because it has to move against a steeper concentration gradient.

B. Ca2+ import into the ER because it has to move against the steeper concentration gradient.

C. H+ import into the vacuole because it is monovalent & Ca2+ is a divalent cation.

D. ΔGc is the same for both ions as their concentration gradients are the same.

E. Insufficient information provided to answer this question.

Hint 17

D

Front 18

Why do K+ channels exclude Na+ ions?

Back 18

A. Na+, but not K+ is always associated with Cl- so it can only be transported as NaCl

B. Dehydrated Na+ is smaller than dehydrated K+ so it cannot coordinate with carbonyl oxygens in the selective filter.

C. K+, but no Na+ retains its bound H20 molecules within the selective filter

D. K+ channels don't exclude Na+ ions and can be used for both K+ export and Na+ import ensuring E-cell remains constant

E. Dehydrated Na+ is larger than dehydrated K+ so it cannot fit into the selective filter

Hint 18

B

Front 19

Which of the following pairs of transport processes have a positive ΔGm in a typical cell?

Back 19

A. Na + import and Cl- export

B. Ca2+ import and H20 export

C. Cl- and HC03- export

D. Na+ export and Cl- import

E. Na+ and K+ import

Hint 19

D

Front 20

Which of the following would result in GLUT1 deficiency syndrome?

Back 20

A. Nonconservative amino acid substitutions that increase Km of the GLUT1 transporter.

B. Nonconserative amino acid substitutions that reduce Km of the GLUT1 transporter.

C. Overexpression of normal GLUT1 receptors.

D. (a) & (c)

E. (b) & (c)

Hint 20

A

Front 21

How would treating a cell with Valinomycin affect E-cell and the activity of voltage-gated (v-g) K+ channels?

Back 21

A. E-cell becomes more negative; K+ channels open

B. E-cell becomes more positive; K+ channels open.

C. Valinomycin doesn't affect E-cell; K+ channels are unaffected

D. E-cell becomes more positive; K+ channels close

E. E-cell becomes more negative; K+ channels close.

Hint 21

E

Front 22

In the figure shown below, what explains the change in K+ conductance if Ecell moved from 0 mV towards -50 mV?

https://collab.itc.virginia.edu/access/content/attachment/d92f63b2-7cdb-4381-a8a2-5f99559813a0/Tests%20_%20Quizzes/698deb7a-39fe-427d-8f0e-5e15e02eaa65/Conductance.pdf

Back 22

A. R residues on the S4 region of voltage gated K+ channels are electrostatically attracted towards the cytosol & close the gate.

B. R residues on the S4 region of voltage gated K+ channels are electrostatically attracted towards the cytosol & open the gate.

C. R residues on the S4 region of voltage gated K+ channels are electrostatically repelled from the cytosol & open the gate.

D. R residues on the S4 region of voltage gated K+ channels are electrostatically repelled from the cytosol & close the gate.

E. None of the above

Hint 22

A

Front 23

What specific steps in the Na+/K+-ATPase transport cycle require hydrolysis of either a phosphoanhydride bond or a mixed anhydride bond? (Obviously both are required for the entire transport cycle to be completed so consider only the specific steps directly affected)

Back 23

A. Phosphoanhydride hydrolysis is required for 3 Na+ to bind; Mixed anhydride hydrolysis is required for 2K+ to bind.

B. Phosphoanhydride hydrolysis is required for 2 K+ to bind;

Mixed anhydride hydrolysis is required for 3 Na+ to bind.

C. Phosphoanhydride hydrolysis is required for 2 K+ to be imported Mixed anhydride hydrolysis is required for 3 Na+ to be exported.

D. Phosphoanhydride hydrolysis is required for 3 Na+ to be exported. Mixed anhydride hydrolysis is required for 2 K+ to be imported.

Hint 23

D

Front 24

Refer to the figure below. What accounts for the rapid decrease in cytosolic [Ca2+] beginning around ~100 msec?

https://collab.itc.virginia.edu/access/content/attachment/d92f63b2-7cdb-4381-a8a2-5f99559813a0/Tests%20_%20Quizzes/d8c4a495-1744-40f4-bdeb-101eee129206/Calcium%20flux.pdf

Back 24

A. Ca2+–ATPase transports Ca2+ from cytosol into sarcoplasmic reticulum (SR) and voltage-gated Ca2+ channels export Ca2+ from cytosol out of cell.

B. Ca2+–ATPase exports Ca2+ from cytosol out of cell and Na+/Ca2+ exchanger transports Ca2+ from cytosol into SR.

C. Ca2+–ATPase exports Ca2+ from cytosol out of cell and Na+/Ca2+ exchanger transports Ca2+ from SR into cytosol.

D. Ca2+–ATPase transports Ca2+ from cytosol into SR and Na+/Ca2+ exchanger exports Ca2+ from cytosol out of cell.

E. Ca2+–ATPase exports Ca2+ from SR out of cell and

Hint 24

D

Front 25

Which of the following would be affected in cardiac muscle cells treated with digoxin?

Back 25

A. Plasma membrane Na+/Ca2+ exchangers are indirectly inhibited; plasma membrane Na+/K+ ATPase is directly inhibited

B. Both voltage-gated Ca2+ channels on the plasma membrane and Ca2+-gated Ca2+ channels on the SR are indirectly inhibited.

C. Both Na+/Ca2+ exchangers and Na+/K+ ATPase are directly inhibited

D. Both SR Ca2+-ATPase and plasma membrane Na+/Ca2+ exchangers are directly inhibited

E. Both voltage-gated Ca2+ channels on the plasma membrane and Ca2+-gated Ca2+channels on the sarcoplasmic reticulum are directly inhibited.

Hint 25

A

Front 26

What does glucose export from intestinal epithelial cells have in common with the glucose import in erythrocytes?

Back 26

A. These 2 processes occur by distinct mechanisms

B. Both utilize symporters

C. Both A and B

D. Both utilize uniporters

E. Both are examples of secondary active transport

Hint 26

D

Front 27

Why are individuals treated with digoxin often hypoglycemic (have low blood glucose)?

Back 27

A. Digoxin directly inhibits glucose import into intestinal epithelial cells.

B. Digoxin directly inhibits glucose import into erythrocytes.

C. Digoxin directly inhibits glucose export from intestinal epithelial cells.

D. Digoxin indirectly inhibits glucose import into intestinal epithelial cells.

E. Digoxin does not affect blood glucose levels.

Hint 27

D

Front 28

Which of the following permit glucose transport between adjacent intestinal epithelial cells?

Back 28

A. Only GLUT2 transporters.

B. Both tight junctions & Adherens junctions.

C. Both 2Na+/glucose symporters & GLUT2 transporters. D. Both Gap junctions & 2Na+/glucose symporters.

E. Both Gap junctions & GLUT2 transporters.

Hint 28

E

Front 29

What is the function of the

glycocaylx on intestinal epithelial cells?

Back 29

A. Increases the number of transporters present on the apical membrane.

B. Attaches both the apical and basolateral membranes to the underlying cytoskeleton

C. Anchors the basal membrane to the underlying connective tissue

D. Forms microvilli to increase surface area and absorptive capacity of the apical membrane

E. Consists of integral membrane proteins that are hydrolytic enzymes that cleave disaccharides and peptides in intestinal lumen to increase amounts available for import

Hint 29

E

Front 30

Which of the following correctly describes ΔGm for glucose import into intestinal epithelial cells and erythrocytes?

Back 30

A. ΔGm for glucose import in both intestinal epithelial cells and erythrocytes is negative.

B. ΔGm for glucose import in both intestinal epithelial cells and erythrocytes is positive.

C. ΔGm for glucose import in both intestinal epithelial cells and erythrocytes is 0.

D. ΔGm for glucose import in intestinal epithelial cells is positive and ΔGm for glucose import into erythrocytes is negative.

E. ΔGm for glucose import in intestinal epithelial cells is negative and ΔGm for glucose import into erythrocytes is positive.

Hint 30

C