8/24 Cell Signaling

Question 1

Define Endocrine

Answer 1

signaling to far away cells through hormones in the blood

Question 2

Define paracrine

Answer 2

localized cell communication through secreted signals

Question 3

Define Autocrine

Answer 3

cells signal themselves in a paracrine way

Question 4

Define Neuronal signaling

Answer 4

similar to endocrine but fast and targeted to specific cells

Question 5

Give an example of Endocrine signaling

Answer 5

Vassopressin and increasing water retention and blood volume

Question 6

Give an example of paracrine signaling

Answer 6

hedgehog, Wnt and TFG-beta are examples

Question 7

give and example of neuronal signaling

Answer 7

cell synapses

Question 8

Diagrmam general G-Protein receptor pathway

Answer 8

a G-Protien receptor binds a ligand, then binds the G-protein, that then binds ATP (alpha subunit) and splits (from the Beta/Gama subunit) to activate something down stream. Then the GTP hydrolyzed, the G-protein sub-units come back together and it can start over.

Question 9

Diagram general receptor tyrosine kinases pathway

Answer 9

When bind ligand the receptors dimerize. The intercellular domains interact as a tyrosine kinases and phosphorylate themselves. adaptor proteins bind and then two big pathways: Ras/MAP kinase (activate ras and lead to cell proliferation) and P13 kinase pathway (that changes PIP2 to PIP3 and activates TOR to lead to growth)

Question 10

Diagram general nuclear hormone receptor pathway

Answer 10

cholesterol derived hormones and other hormones can enter the cell and bind nuclear receptors and directly alter gene transcription. or bind to guanylate cyclase!

Question 11

what kind of reactions are catalyzed by kinases (potential effect)

Answer 11

Protein Kinases phosphorylate target proteins to :

1. change the interaction with other proteins.
2. Change conformation to active or inactive or different substrate
3. Cause it to be digrated

Question 12

what kind of reactions are catalyzed by phosphatases (potential effect)

Answer 12

de-phosphorylation through hydrolyze the bond with water. Reduce a signal or effect caused by a kinase.

Question 13

what kind of reactions are catalyzed by guanylate cyclase (potential effect)

Answer 13

converts GTP into cyclic GMP or cGMP. this can activate protein kinases that phosphorylate targets to cause effect

Question 14

what kind of reactions are catalyzed by adenylate cyclases (potential effect)

Answer 14

leads to the production of cyclic AMP (cAMP) from ATP. This in turn leads to protein kinase A being activated which can affect metabolism by shifting away from storing towards using glycogen

Question 15

what type of reactions are catalyzed by phosphodiesterases (potential effect)

Answer 15

these tend to terminate a signal by degrading the second messenger level. Therefore: stop signal

Question 16

what type of reactions are catalyzed by phospholipases (potential effect)

Answer 16

the hydrolisis of the PIP2 bond, freeing the IP3 from the membrane bound section

Question 17

phospholipase C

Answer 17

activated by a G-protein complex. Hydrolyzes a phosphodiester bond of phosphorylated inositol away from PIP2 this creates IP3 mesanger and DAG that is stuck in the membrane still. IP3 changes allow opening of calcium channels. This turns on calmodulin that acts on many enzymes and transports.

Question 18

how could signaling to a cell membrane receptor be advantageous to signaling to a hormone recewptor inside the cell

Answer 18

secondary messangers can diffuse to other parts of the cell.
The signal can be amplified.
crosstalk can result in input from many pathways connecting to a common second messenger therefore finetune signal.
rapidly degrade the signal by metabolizing second receptors

Question 19

Protein Kinase C

Answer 19

down stream effector of diacylglycerol (DAG)

Question 20

how do g-protein coupled receptor signal terminate

Answer 20

Galpha subunit hydrolyzes the bound GTP to GDP. Ligan disociated from receptor. internalize the receptor or break down the effectors etc.