Cell signaling

Question 1

T/F G proteins do not synthesize GTP from GDP + Pi

Answer 1

True

Question 2

Signal transduction is initiated by the binding of ____ to receptor molecules in the plasma membrane.

Answer 2

Ligands.

Question 3

T/F Multiple lipid-derived messengers are produced in membranes.

Answer 3

True

Question 4

Why are phosphorylation cascades a common feature of cellular signal transduction?

Answer 4

They amplify signal many times.

Question 5

T/F PLCs release soluble lipid second messengers in response to diverse inputs.

Answer 5

True

Question 6

T/F Phospholipases D and A2 create other lipid second messengers.

Answer 6

True

Question 7

What is the description of an agonist

Answer 7

Initiates signal activation

Question 8

T/F All G proteins are enzymes.

Answer 8

True

Question 9

G proteins bind to both GTP and GDP but not simultaneously. T/F

Answer 9

True

Question 10

What is an autocrine signaling?

Answer 10

Self stimulation of growth.

Question 11

PI3 Kinase synthesizes PIP3 to modulate cell shape and motility. T/F

Answer 11

True

Question 12

Binding of a signaling molecule to a _____ leads directly to a change in distribution of ions across the membrane?

Answer 12

Receptor protein

Question 13

G proteins are phospohorylated by GTP. T/F

Answer 13

False,

They are phosphorylated by GDP

Question 14

ij

Answer 14

G alpha subunits bind to GTP

Question 15

What is the function of a protein phosphatase?

Answer 15

Reverse Kinase action by removing a phosphate

Question 16

G proteins change their shape when they release GDP and then bind to GTP. T/F

Answer 16

True

Question 17

What are the steps occurring following binding of ligand to receptor tyrosine kinases?

Answer 17

Kinase activated —> Phosphorylation of tyrosine —-> phosphate activates signaling proteins

Question 18

What is the source for cAMP?

Answer 18

Adenylyl cyclases synthesized from ATP.

Question 19

Why are serine, threonine and tyrosine the only amino acids that can be phosphorylated by protein kinases?

Answer 19

Because they contain -OH group which can be replased w/ phosphate

Question 20

What is paracrine signaling?

Answer 20

Signaling between neighboring cells.

Question 21

Describe the mechanism of activation of heterotrimeric G proteins.

Answer 21

GDP is attached to a protein scaffold, when stimuli comes around GDP turns to GTP, beta and gama subunits leave. Alpha subunits attaches to adenyl cyclase which activates ATP to make cAMP, cAMP then activates Kinase.

GTP– GDP — Alpha + Adenyl cyclase – ATP — cAMP — Kinase activation.

Question 22

Which amino acids can be phosphorylated by protein kinases?

Answer 22

Serine, threonine and tyrosine

Question 23

The function of a protein phosphatase is to ____.

Answer 23

Remove phosphate and reverse kinase action

Question 24

How does binding GTP control the activity of G proteins?

Answer 24

Activate protein.

Question 25

Which signaling molecules stimulates a rise in cytosolic cAMP in animal cells?

Answer 25

Toxins, Theophylline, Caffeine, Adrenaline

Question 26

Find examples of “positive feedback” in a cell.

Answer 26

output enhances original signal.

blood clots

Question 27

What happens when a “G protein” Cleaves GTP to GDP?

Answer 27

Alpha and beta subunits are dissociated

Question 28

Why does signaling through a peptide growth factor allow for more rapid responses in a cell than signaling through a steroid hormone such as estrogen?

Answer 28

Because it is bound to a membrane and has a scaffold.

Question 29

Which signaling molecules stimulates a rise in cytosolic Ca 2+?

Answer 29

cAMP via PKA

Question 30

What is the source for this Ca2+ (where is it stored)?

Answer 30

Endoplasmic reticulum.

Question 31

Inositol triphosphate is a product of which enzymes?

Answer 31

Phopholipase (PLCs)

Question 32

What makes adenylate cyclase a signaling protein?

Answer 32

Makes cAMP which triggers other responses.

Question 33

List the secondary messangers

Answer 33

Ca 2+, IP3, cAMP

Question 34

The mitogen-activated protein kinases are among the most commonly used proteins kinases in cells. They are often employed by the cell in protein kinase cascades, where MAP3K phophorylates and activates MAP2K, which in turn phosphorylates MAPK. What are the possible advantages for the cell to employ a protein kinase cascade?

Answer 34

Cell proliferation
Differentiation
Cell survival.