CH 16

Question 1

Signal Transduction:

Answer 1

the process whereby one type of signal is converted into another

Extracellular signal molecule -> creates intracellular signaling molecule

Question 2

4 types of signalling

Answer 2

1) Endocrine - hormones
*not every cell will respond to these hormones, only target

2) Paracrine - Cell reacts to local mediators produced by itself
*autocrine signaling

3) Neuronal - long distance to specific target
*Transmitted along axons
*when signal reaches end, releases neurotransmitters

4) Contact-dependent - Face to Face
*Cells make contact
*signaling molecule is membrane bound

Question 3

Extracellular signals are received by what type of molecule

Answer 3

Large hydrophilic molecules that can’t cross membrane
on outside of cell

Question 4

Intracellular receptors receive signals from what type of molecule

Answer 4

small hydrophobic molecules that can pass membrane

Question 5

acetylcholine effects on different cells

Answer 5

Acetylcholine can be received by many cells and have different responses

Saliva secretion, Dec heart rate, contraction

Question 6

3 types of signals animal cells depend on

Answer 6

1) Survival
2) Growth and division
3) differentiation

Question 7

What happens if cells are deprived of signaling

Answer 7

Apoptosis - Cell Death

Question 8

Speed of Cellular response to signaling?

Answer 8

Slow or Rapid

Cell growth, division, Differentiation are Slow

Movement, secretion, metabolism are Rapid

Question 9

Many Extracellular signals can activate or start…

Answer 9

Intracellular pathways to change the behavior of the target cell, the pathway eventually reaches an effector protein

Question 10

Intracellular signaling proteins can do what from signals
(5 Things)

Answer 10

relay, amplify, integrate, distribute, and modulate feedback via signals

Question 11

Relay Function

Answer 11

propagate the signal to other molecules (pass a baton), can
be helped by scaffold proteins that bring together signal carrying
components

Question 12

Amplify Function

Answer 12

make the signal stronger to create a large response

Question 13

Integrate` Function

Answer 13

take in multiple different signals before passing on another signal

Question 14

Feedback Function

Answer 14

modulate responses to slow down/speed up signal transduction

Question 15

Positive feedback

Answer 15

Product induces the reaction pathway to keep it going

Question 16

Negative feedback

Answer 16

Product inhibits its own production loop

Question 17

2 regulatory GTPase proteins are…

Answer 17

GEFs) promote exchange of GDP for GTP to turn on

GAPs) Promote hydrolysis of GTP to GDP turning it off

Question 18

3 classes of Cell-Surface receptors

Answer 18

1) Ion-channel-coupled receptors
2) G-couple protein receptors
3) Enzyme-coupled receptors

Question 19

Morphine and Heroine receptor action

Answer 19

stimulate G-protein-coupled opiate receptors

Question 20

Valium and Ambien receptor action

Answer 20

Stimulate GABA activated ion channel coupled receptors

Question 21

G-Protein Coupled receptors
(Functions and structure)

Answer 21

• all the same structure, 7 transmembrane alpha helces

*mediate many functions

Question 22

What does stimulation of GPCRs do?

GPCR = G-Protein coupled receptors

Answer 22

activates G-protein subunits

Signalling molecule binds, conformational change occurs and releases molecule on cytosolic side

Question 23

How many subunits do G proteins have

Answer 23

G proteins all have 3 subunits (a, b, y)

Question 24

b and y subunit function in G protein

Answer 24

Tethered to plasma membrane by lipid tails on the y subunit

Question 25

Activation of GPCR causes...

Answer 25

alpha subunit of G protein to lose affinity for GDP and exchange for GTP Activation causes the alpha subunit to detach from b and y

Question 26

How does an activated G protein go back to inactive conformation?

Answer 26

GTPase will hydrolyse alpha subunit to convert GTP to GDP to return to inactive conformation

Question 27

How long does alpha subunit stay on? How does it deactivate?

Answer 27

as long as it is bound to target protein, It deactivates by hydrolyzing itself and then re-associates with b and y subunit.

Question 28

How do Toxins cause disease

Answer 28

alters activity of G proteins, locks G proteins in certain states

Question 29

Cholera toxin:

Answer 29

modifies alpha subunit, stimulates adenylyl cyclase *Makes ATP turn into cAMP, activates Cl channel causing Cl- to flow out of cell

Question 30

Pertussis toxin

Answer 30

alters alpha subunit, inhibits adenylyl cyclase, locking it into an inactive state causing cough.

Question 31

G proteins can also regulate...

Answer 31

ion channels ~20 different g proteins are ion channels or enzymes in membrane in mammals

Question 32

what can the b.y complex do to ion channels

Question 33

Enzyme coupled receptors (RTKS)

Answer 33

RTKs, receptor tyrosine kinases -single pass transmembrane -when activated form dimers -phosphorylate eachother after dimerization -class of enzymes

Question 34

Ras:

Answer 34

small monomeric GTP-binding protein attached by lipid tail *faces cytosolic side *resembles alpha subunit of GCPRs *active with GTP bound

Question 35

GTP vs ATP switches

Answer 35

switch is turned on or off by phosphate or lack of phosphate group Switch is turned on or off by entire GDP or GTP molecule

Question 36

Causes of activations of G proteins

Answer 36

1) Can cause enzymes to make second messengers -Response amplification 2) Open ion channels (pacemaker example)

Question 37

Second messengers can do what

Answer 37

activate other proteins cause: changes metabolism, effect transcription

Question 38

Enzyme-Coupled Receptors function:

Answer 38

Important for growth & division Prevent cell death (apoptosis)

Question 39

what encourages RAS to exchange GDP for GTP?

Answer 39

GEF

Question 40

What turns RAS off?

Answer 40

GAPs, GTPase

Question 41

Enzyme coupled receptor process

Answer 41

Signal molecule on RTK --> Dimer forms --> dimers phosphorylate eachother ---> Ras-GEF turns on, activates RAS ---> RAS signals MAP-kinase

Question 42

what is MAP kinase

Answer 42

Mitogen activated protein, phosphorylates multiple further molecules and activator proteins.