Signals

Question 1

generic signaling pathway

Answer 1

1. Signal (extracellular signal molecule)
2. Reception (receptor protein
3. Interpretation (intracellular signaling proteins activate/deactivate effector proteins)
4. Biological response (caused by receptor proteins)

Question 2

G-Protein-Coupled Receptors

Answer 2

Starts: inactive receptor + inactive G protein + inactive enzyme

1) signal molecule binds to an activated receptor that has an inactive G-protein attached to it - this activates the G-protein
2) inactive enzyme activated by G protein

Question 3

Guanine	nucleotide
exchange factors (GEFs)

Answer 3

promotes GDP->GTP

exchange

Question 4

GTPase-activating

Protein (GAP)

Answer 4

promotes GTPase activity

Question 5

Three classes of intracellular signaling proteins

Answer 5

GTPases (G proteins)

Kinases and their protein targets

Other enzymes and their small molecule products

Question 6

Epinephrine signaling from GPCR

Answer 6

1) signal molecule activates GPCR
2) activated GPCR activates G protein
3) G protein activates adenylyl cyclase
4) ATP hydrolysis using the enzyme adenynyl cyclase makes cAMP
5) cAMP activates PKA

Question 7

Compare and contrast the role of GTP hydrolysis to ATP hydrolysis by intracellular signaling proteins (GTPases and kinases, respectively) in signal transduction

Answer 7

GTP hydrolysis activates the enzymes responsible for ultimately activating kinases

(PKA for example)

Kinases sometimes act in a kinase cascade

Question 8

second messengers

Answer 8

second messengers are produced by activated enzymes. these second messngers act in turn to activate other proteins in the same cell

(adenynyl cyclase, for example)

Question 9

What do scaffold proteins do?

Answer 9

They promote specificity and efficiency of signal transduction by bringing them close in proximity

Question 10

In regards to one specific signal, what things can be altered by cell-specific differences in gene expression or other signals

Answer 10

Interpretation + response.

The same signal can cause different things in different cells because of a difference in gene expression or other signals

Question 11

What do effector proteins do?

Answer 11

They are the enzymes at the end of the chain cause the biological response in question

Question 12

Heterotrimeric G proteins

Answer 12

Heterotrimeric G proteins use GTP to activate enzymes