15A Assignment

Question 1

A GAP…….

stimulates the exchange of bound GDP for GTP.

enhances the GTP hydrolysis rate of monomeric GTPases.

inhibits the GTPase actvity of monomeric GTPase.

is a factor without which monomeric GTPases cannot hydrolyze GTP.

Answer 1

enhances the GTP hydrolysis rate of monomeric GTPases.

Question 2

An extracellular signal that is in the vicinity of the cell that secretes it and thereby activates signaling in the surrounding cells is classified as:

paracrine signaling

endocrine signaling

autocrine signaling

synaptic signaling

Answer 2

paracrine signaling

Question 3

Endocytosis of receptors followed by degradation in lysosomes in response to a signal is a mode of

receptor activation

positive feedback mechanism

receptor desensitization

Answer 3

receptor desensitization

Question 4

Which of these domains bind to proline-rich sequences?

SH3 domain

PTB domain

PH domain

SH2 domain

Answer 4

SH3 domain

Question 5

Which of these is not a type of Receptor?

Ligand-gated ion channels

GPCRs

Enzyme-coupled receptors

monomeric G proteins

Answer 5

monomeric G proteins

Question 6

Which of these responses to a signal are likely to occur in seconds?

Translation

Transcription

Protein phosphorylation

Altered cell growth

Answer 6

Protein phosphorylation

Question 7

Which of these statements is false?

Phosphatases catalytically remove the phosphate from GTP in GTP-binding proteins.

Serine-specific kinases or threonine-specific kinases are common types of protein kinases.

For activation of GTP-binding proteins, the GDP is exchanged for GTP.

Answer 7

Phosphatases catalytically remove the phosphate from GTP in GTP-binding proteins.

Question 8

__________________ cells in select tissues release hormones that are distributed to the rest of the body.

Paracrine

Autocrine

Endocrine

Local Mediators

Answer 8

Endocrine

Question 9

Among which of these signaling mechanisms (other than endocrine signaling) do signaling molecules move farthest away from the cells that release them?

Paracrine

Neuronal (synaptic)

Contact-dependent

Autocrine

Answer 9

Paracrine

Question 10

Which of these are secreted extracellular signaling molecules that work only in the neighborhood they are released in?

Hormones

Local mediators

Receptors

Answer 10

Local mediators

Question 11

Electrical impulses sent along a neuronal axon reaches the synapse and triggers secretion of a chemical called………..

Neurotransmitter

Nucleotides

Receptors

GTPases

Answer 11

Neurotransmitter

Question 12

Charged phosphoinositides are recognized and bound by

SH2 domains

Pleckstrin Homology domain

SH3 domain

PTB domain

Answer 12

Pleckstrin Homology domain

Question 13

Scaffold proteins affect amplification and speed of signal by………………

limiting amplification but improving speed.

enhancing amplification similar to diffusible messengers and enhacing speed.

limiting amplification and speed.

improving amplification similar to diffusible messengers but limiting speed.

Answer 13

limiting amplification but improving speed.

Question 14

Src Homology Domains (SH2) bind to which of these residues on activated receptors?

Serine

Arginine

Phosphorylated Tyrosine

Ubiquitinated lysine

Answer 14

Phosphorylated Tyrosine

Question 15

Activation of which of these proteins leads to the activation of a monomeric GTPase by releasing GDP and binding GTP.

Guanine nucleotide exchange factor (GEF)

GTPase-activating protein (GAP)

Scaffold protein

Adaptor

Answer 15

Guanine nucleotide exchange factor (GEF)

Question 16

Which of these enzymes phosphorylate a protein by transferring the terminal phosphate from ATP onto a serine, threonine or tyrosine residue?

Kinase

Phosphatase

Monomeric GTPase

Ligase

Answer 16

Kinase

Question 17

A signaling molecule can generate a strong signaling response that persists even after the signaling molecule is removed and this can be due to:

Positive feedback

Negative feedback

No feedback

Answer 17

Positive feedback

Question 18

Amplification of response to a signal can be generated when receptor activation leads to generation of a large number of intracellular signaling molecules/chemicals called…………….

kinases.

first messengers.

intracellular receptors.

second messengers.

Answer 18

second messengers.