Chapter 5: Signal Transduction

Question 1

*Signal Transduction

Answer 1

transmition of extracellular signal throughout a cell to make a chemical/ cellular change
ex. metabolism, gene expression

Question 2

What effects can ligands/ receptors have?

Answer 2

they may lead to activation or inhibition of downstream signaling

Question 3

*G protein

Answer 3

membrane anchored heterotrimers

Question 4

*What are the types of alpha subunits?

Answer 4

alpha s, alpha I, and alpha q

Question 5

*alpha s subunit

Answer 5

activates adenylate cyclase

Question 6

*alpha I subunit

Answer 6

inhibits adenylate cyclase
- bind to adenylate cyclase and inhibits it

Question 7

*alpha q

Answer 7

activates or inhibits phospholipase C

Question 8

*Signal Amplification

Answer 8

cascade/ 1 ligand binding can lead to a quick and fast response (activating multiple downstream targets)

Question 9

*Secondary Messenger

Answer 9

A natural chemical which is produced by the cell as a result of receptor activation, and which carries the chemical message from the cell membrane to the cytoplasm
-small molecules implicated in signal transduction, helps amplify signal
- ex: cAMP

Question 10

*cAMP

Answer 10

cyclic AMP; secondary messenger

Question 11

*Adenylate Cyclase

Answer 11

bound to the membrane and once activated, produces cAMP

Question 12

*PKA

Answer 12

Protein kinase A

Question 13

*Kinase Cascade

Question 14

*Phospholipase C

Answer 14

When activated, it cleaves a membrane embedded molecules PIP2 into two signaling molecules: DAG and IP3

Question 15

*PIP2/IP3

Answer 15

signaling molecules

Question 16

*GTP/GDP

Answer 16

key molecules used in signal transduction

Question 17

Regulation

Answer 17

key to control

Question 18

Stage 1 of GPCR Signal Transduction

Answer 18

1. GPCR binds a ligand on the extracellular side and a conformational change on the intracellular side opens a binding site for a G-protein (specific G protein depends on the type of receptor
2. G protein bind to the GPCR
3. GDP is released from the alpha subunit
4. The alpha subunit bind GTP, destabilizing the trimer, which breaks up into an alpha subunit and a beta gama (BY) dimer
5. The dissociated alpha subunit and a BY dimer dissociate from GPCR

Question 19

Stage 2 of GPCR Signal Transduction

Answer 19

1. the next stage of GPCR signal transduction depends on the specific type of alpha subunit associated with GPCR.

Question 20

How does alpha s subunit work?

Answer 20

-when bound to GTP and dissociated from BY binds to adenylate cyclase, activating it
-Adenylate cyclase is bound to the membrane and once activated produces cAMP (a secondary messenger)
- after a while GTP is hydrolyzed to GDP and alpha s reassociates with BY back to an inactive heterodimer

Question 21

Phosphorylation

Answer 21

adding a phosphate

Question 22

What do Kinases do?

Answer 22

transfer a phosphate groups from ATP to a target compound

Question 23

What do phosphorylase enzymes do?

Answer 23

remove phosphates

Question 24

What happens if the GPCR binds to a Gq protein?

Answer 24

-If the GPCR binds to a Gq protein, the alpha q subunit will dissociate and activate or inhibit phospholipase C
- Activated phospholipase C cleaves a membrane embedded molecule PIP2 into two signaling molecules: diacylglycerol (DAG) and IP3

Question 25

What does an increase in cAMP cause?

Answer 25

leads to glycogen breakdown by activating a kinase cascade