Exam 2 quizzes and hotseat questions

Question 1

E3 ligases do not:

A) Transfer ubiquitin to a lysine on the target substrate

B) Confer specificity within the UPS

C) Transfer ubiquitin from a cysteine on E2

D) Bind substrates based on specific recognition motifs

E) Only recognize misfolded proteins

Answer 1

E) Only recognize misfolded proteins

Question 2

The reason Lys acetylation leads to loosening of the nucleosome and gene activation is…

A) the histone-DNA interaction is weakened because Lys is not charged

B) it causes histones to interact with the C-terminal domain of RNA poly 2

C) due to electrostatic repulsion between histones and DNA

D) it facilitates methylation of DNA

Answer 2

A) the histone-DNA interaction is weakened because Lys is not charged

Reason: lysine is charged so adding an acetyl neutralizes the interaction.

Question 3

Transcription and replication both:

A) Use both DNA strands for synthesis

B) Require phosphorylation for activation

C) Use a primer to initiate synthesis of new strands

D) Occur mainly in S phase of the cell cycle

Answer 3

B) Require phosphorylation for activation

Question 4

Restriction of DNA replication to once per S phase of the cell cycle is controlled by..

A) The formation of the ORC complex

B) The assembly of the MCM2-7 complex

C) Phosphorylation of the licensing factors

D) Recruiting the replisome can occur only once

E) Regulation of replisome transcription

Answer 4

C) Phosphorylation of the licensing factors

Question 5

Which of the following signal pathways is depicted here? (Slide 24: Lecture 2 Sjogren)

A) angiotensin 2 receptor signaling

B) Beta2-adrenergic receptor signaling

C) alpha2-adrenergic receptor signaling

D) Insulin receptor signaling

Answer 5

B) Beta2-adrenergic receptor signaling

Reason: angiotensin 2 receptor signaling is not Gs coupled, alpha2-adrenergic receptor signaling is Gi coupled so has the opposite effect and Insulin receptor signaling is not a GPCR pathway.

Question 6

What is the likely Kd of calmodulin for Ca2+?

A) 10^-3

B) 10^-4

C) 10^-6

D) 10^-8

Answer 6

C) 10^-6

Reason: ratio 10^4.

Inside 10^-7 and outside is 10^-3

Small increase to 10^-6 rapidly activates

Question 7

Which subunit (alpha, Beta, gamma) of the trimeric G protein is likely to be similar in structure to the monomeric G protein?

A) Galpha

B) GBeta

C) Ggamma

Answer 7

A) Galpha

Reason: GTP and GDP also bind to Galpha so they are similar.

Question 8

In neutrophil migration, which interaction is most important to ensure neutrophils can cross the endothelium?

A) S-LeX and selectin

B) LFA-1 and ICAM-1

C) CXCL8 and CXCL8 receptors

D) All of these interactions

Answer 8

B) LFA-1 and ICAM-1

Reason: important interaction that ties neutrophils to where cytokines are.

Question 9

Besides receptor internalization, another way to terminate the signaling from receptor tyrosine kinases could be…

A) Membrane voltage

B) GTP to GDP hydroylsis

C) Receptor saturation

D) Protein phosphatase as part of a protein phosphorylation cycle

Answer 9

D) Protein phosphatase as part of a protein phosphorylation cycle

Question 10

Select the statement that accurately describes signal transduction

A) sender cells secret second messenger ligands that are received by target cells

B) a signal transduction pathway is described generally by three components: reception of an extracellular signal, intracellular transduction of that signal by a series of reactions to synthesize a second messenger, and the cellular response

C) initiated by ligand binding to a receptor on the target cell but does not require receptor saturation to reach 100% of the cellular response level

D) occurs mostly during development

Answer 10

C) initiated by ligand binding to a receptor on the target cell but does not require receptor saturation to reach 100% of the cellular response level

Question 11

Steroid hormones, such as estrogen, bind nuclear receptors in the cytoplasm and move into the nucleus to regulate gene expression. The mode of cell-cell communication for this signaling is

A) autocrine

B) paracrine

C) endocrine

D) juxtacrine

E) neuronal

Answer 11

C) endocrine

Question 12

Amplification in signal transduction refers to

A) an on/off cycle as in the case of GTPases

B) the growth factor ligand binding specifically to a receptor tyrosine kinase on the target cell

C) the signal transduced by the agonist binding to a GPCR

D) signal transduced to one molecule is highly regulated and specific

E) signal from a sender cell is transduced in a cascade to the target cell

Answer 12

C) the signal transduced by the agonist binding to a GPCR

Question 13

The statement that does NOT accurately describe GPCRs

A) No enzyme activity

B) There are ~1000 GPCRs with high structural similarity

C) Are active in numerous signaling processes for hormone function, prostaglandin function, etc

D) Activation causes multiple proteins to associate into a large assembly of signaling proteins

E) Associates with hetero-trimeric G proteins to promote GDP release

Answer 13

D) Activation causes multiple proteins to associate into a large assembly of signaling proteins

Question 14

Ras is a signaling protein that

A) when bound with GDP interacts with numerous downstream proteins

B) switches between two conformations depending on the bound nucleotide

C) has transmembrane helices

D) gets internalized to terminate signaling

E) phosphorylates downstream signaling proteins

Answer 14

B) switches between two conformations depending on the bound nucleotide

Question 15

All below mechanisms contribute to termination of GPCR-mediated signal transduction EXCEPT:

A) Acceleration of GTPase activity by RGS proteins

B) Breakdown of cAMP by PDE

C) Phosphorylation of the GPCR by GRK

D) Exchange of GDP for GTP on Gα

E) β-Arrestin binding to the GPCR

Answer 15

D) Exchange of GDP for GTP on Gα

Question 16

The choice that does not accurately describe cytokine receptors

A) some have intracellular Ig domains

B) transmembrane proteins with extracellular, intracellular and transmembrane regions

C) diverse number of extracellular domains

D) can bind more than one kind of cytokine, even as many as ten different cytokines

E) can have long disordered regions ranging over 600 residues

Answer 16

A) some have intracellular Ig domains

Question 17

If the common gamma chain acquired a mutation that inhibited PI3K/Akt signaling, the cell would be more likely to ____

A) survive

B) undergo apoptosis

C) lose transcriptional activity

D) undergo cell division

E) remain unaffected

Answer 17

B) undergo apoptosis

Question 18

Cytokines are proteins that

A) are rarely linked to disease but have been targeted for cancer and autoimmune treatment.

B) bind an extracellular receptor on only one specific type of cell, most of these cell types being in the immune system

C) have diverse function, including one protein that can be either anti-inflammatory or pro-inflammatory.

D) have similar molecular weight and mostly helical structure.

Answer 18

C) have diverse function, including one protein that can be either anti-inflammatory or pro-inflammatory.

Question 19

cAMP is a second messenger that:

A) activates adenylate cyclase

B) binds the catalytic domain of PKA

C) leads to phosphorylation of cytoplasmic and nuclear proteins by PKA

D) creates a membrane docking site for signaling proteins

E) is generated by adenylate cyclase by cyclizing 5’-AMP

Answer 19

C) leads to phosphorylation of cytoplasmic and nuclear proteins by PKA

Question 20

Inositol tri-phosphate, IP3, is produced by which enzyme activity?

A) GTPase

B) adenylate cyclase

C) tyrosine kinase

D) calmodulin

E) phospholipase C

Answer 20

E) phospholipase C

Question 21

Which of the following enzymes phosphorylate licensing factors to initiate replication?

A) CDK2

B) CDC45

C) Cdc6

D) Cyclin A

E) Cyclin H

Answer 21

A) CDK2

Question 22

In Gq signaling, cytoplasmic calcium levels increase as a result of

A) active transport driven by the high calcium concentration in the extracellular space

B) binding of Gαq to adenylate cyclase

C) phosphorylation of G-proteins

D) passive diffusion of calcium from the ER through gated channels

E) calcium pumps

Answer 22

D) passive diffusion of calcium from the ER through gated channels

Question 23

Cell surface receptors with seven transmembrane domains signal by

A) acting as a guanine nucleotide exchange factor

B) tyrosine phosphorylation

C) opening a calcium channel

D) binding to and co-localizing several proteins

E) acting as a GTPase

Answer 23

A) acting as a guanine nucleotide exchange factor

Question 24

Gleevec (imatinib) treatment produces a prolonged remission (but not a cure) of most cases of CML. In all the responsive cases, the Abl tyrosine protein kinase activity in the cancer cells has been activated by

A) increased transcription

B) mutational activation of the activation loop

C) mutational activation of an upstream activating protein kinase

D) aberrant recombination that caused loss of the inhibitory domain from the catalytic domain

E) gene duplication

Answer 24

D) aberrant recombination that caused loss of the inhibitory domain from the catalytic domain