signal transduction

Question 1

What are the three main parts to any “classic” Signal Transduction Pathway

Answer 1

Reception: Binding of signaling molecule to a receptor
Transduction: Bring information into the cell
Response: Activates response to new information

Question 2

What is the basic mechanism for ligand gated channels

Answer 2

We have a closed-channel protein that is turned on by a signaling molecule(ligand).
When binds, conformational changes in the protein and will open. Ions can stream into cells. Ions can enter and elicit different cellular responses

Question 3

How do they get “turned off”?

Answer 3

When a ligand loses affinity and falls off receptor

Question 4

What is the basic mechanism for G-Protein Coupled Receptors

Answer 4

G protein that is bound to GDP. Receptor bound to g protein. GDP=off. A signal is received a conformation change. GDP to GTP. GTP=on. Once it’s on, alpha and beta gamma subunits (they are tethered to the membrane) move until it reaches an enzyme. The alpha unit reaches an enzyme, and a second messenger is released to trigger responses

Question 5

What is a G-protein, and what is it made of

Answer 5

trimer- alpha, beta, gamma subunits

Question 6

How do G-Protein Coupled Receptors get turned of

Answer 6

Gtp is hydrolyzed to GDP by alpha sub unit. Signaling molecule falls off.

Question 7

What is the basic mechanism for Receptor Tyrosine Kinases?

Answer 7

There are two receptors tyrosine kinase proteins. Signaling molecule (ligand) comes and binds to binding site.
Cause a conformational change “dimerize”. Two proteins will move together
Fully activated when 6 ATP drops off its phosphates at the protein complexes (ATP will turn to ADP)

Question 8

How do they get turned off (transiently)

Answer 8

Can turn off when signaling molecule falls off and then have an enzyme come in to cleave off phosphates - phosphatase

Question 9

What unique feature can turn of RTK’s permanently

Answer 9

A lysosome can recycle

Question 10

Defects in RTK’s often show up in what disease state

Answer 10

Cancer

Question 11

For 2nd Messengers, what are the two most common second-messenger molecules?

Answer 11

cAMP
Calcium iosn

Question 12

How does cAMP get formed, and how is it “turned off”?
What enzyme forms cAMP, and where is it located?

Answer 12

ATP is turned to cAMP by pyrophosphate. two phosphates are cut off, to break up cAMP, phosphodiesterase breaks apart cAMP to make AMP

Question 13

Kinase Cascades (aka Phosphorylation Cascades), what are some of the advantages of a cascade of enzymatic reactions?

Answer 13

signal amplified

Question 14

How do some Kinase Cascades enhance the rate of signal transduction? What protein do they utilized to speed up the reaction and how does that work? b. How do Kinase Cascades turn themselves off? Is it enough to turn off the first step in the cascade?

Answer 14

signaling molecule will activate a relay molcule which can then cause to activate layes of protein kinases. Attp will phosphirilate causing a conformation change to protein kinases. Active protein kinases can turn on several more proteins that will cause cellular responses. Aplify signal all the wwyay down
To turn off, all levels have to be turned off. We need a phophotase to cleave off organic phosphate on protein kinases to turn off

Question 15

What are some of the different general areas that we could see a cellular response

Answer 15

Metabolic pathways
Cytoskeleton movement
Transcription regulation

Question 16

Be able to explain different examples of Coordination between different response pathways and how they can modulate any single pathway’s response.

Answer 16

Response one: Simple as a receptor binding to a signaling molecule to a receptor and creating a through relay molecules.
Two: signaling molecule binding to receptor and relay molecules branching off to make two responses.
Three: Cross-talk: where a different receptor and dif signaling molecule will cut off another signal. Activation or inhibition
Four: A different signaling molecule and receptor lead to different relay molecules that will lead to different responses.

Question 17

Yeast reproduction

Answer 17

Yeast can reproduce sexually. A and alpha cells. It will start to
A will release signaling molecule and also express receptors on its surface for the opposite mating type (alpha)
Once picked up, they mate and fuse into a hybrid , a slow response

Question 18

What benefit does this process confer on the yeast progeny

Answer 18

Its to improve genetic diversity

Question 19

What is adrenaline and where is it made?

Answer 19

Made stored and excreted in endocrine cells
Can go anywhere in the body relatively quicky and long distances
Binds to gPCR
Impact over 1700 different responses

Question 20

Which relay molecule is most commonly involved in these responses?

Answer 20

cAMP

Question 21

fast response adrenaline

Answer 21

Adrenaline binds to GPCR and activated alpha subunit of G protein. G protein activats adenylyl cyclase which can turn ATP to cAMP. cAMP turns inactive PKA to active PKA.
PKA takes ATP and releases a phosphate to inactive protein to turn on (cascade)
Glycogen degrading enzyme turned on by phospholation to break down glycogen. Liberate glucose to be used to make ATP to make energy

Question 22

slow response adrenaline

Answer 22

Slow: Adrenaline binds to GPCR and activated alpha subunit of G protein. G protein activats adenylyl cyclase which can turn ATP to cAMP. cAMP turns inactive PKA to active PKA. Active PKA is free floating and can enter nuclear pore where it can activates transcription .