Signal Transduction

Question 1

TRUE or FALSE: Signaling pathways consist of a series of proteins. Each protein in a pathway alters the conformation of the
next protein, usually via phosphorylation

Answer 1

TRUE

Question 2

signal transduction is initiated by binding of a ligand (which can be ???) to its receptor (cell surface or intracellular)

Answer 2

(soluble or membrane-bound)

Question 3

autocrine signal transduction = ???

Answer 3

self phosphorylated

Question 4

??? = signal molecule fits binding site on complementary receptor perfectly

Answer 4

specificity

Question 5

Key features of signal transduction:
1. specificity
2. ???
3. desensitisation/adaptation

Answer 5

amplification

Question 6

desensitisation occurs when a receptor is shut down or ???

Answer 6

removed from cell surface

Question 7

TRUE or FALSE: Cell signalling cannot vary in response to the same
extracellular messenger

Answer 7

FALSE, it can vary

Question 8

acetylcholine is an example of how cell signalling varies in response to same messenger due to its effect in:
- cardiac muscle = ???
- skeletal muscle = decreased contractile rate and force
- salivary glands = secretion

Answer 8

increased contractile rate and force

Question 9

Signalling pathways often involve protein kinases and ???

Answer 9

phosphatases

Question 10

GPCRs: signal transducer that when bound to an external ligand, causes ??? to an effector enzyme to cause an effect which generates secondary messenger cascade

Answer 10

intracellular G-protein binding

Question 11

Receptor Tyrosine Kinase: signal transducer that autophosphorylates when ligand binds to it, causing ???

Answer 11

kinase cascade

Question 12

receptor guanylyl cyclase: when a ligand binds, it activates formation of ???

Answer 12

second messenger cAMP

Question 13

adhesion receptor (integrin) binds molecules in ???, changes conformation, and thus alters its interaction with the cytoskeleton

Answer 13

extracellular matrix

Question 14

nuclear receptor: ??? binding allows receptor to regulate expression of specific genes

Answer 14

steroid

Question 14

gated ion channel opens or closes in response to ???

Answer 14

concentration of signal ligand or membrane potential

Question 15

GPCRs bind to g proteins and are activated by Extracellular messengers including ???, ??? chemokines, nucleotides, light, ordants (smell) and tastants (taste)

Answer 15

hormones, neurotransmitters

Question 16

GDP is bound to the ??? subunit and is displaced by GTP = ON switch. Hydrolysis of the bound
GTP to GDP = OFF switch

Answer 16

α subunit

Question 17

which subunit of the GPCR dissociates upon activation of GPCR and goes off to activate the effector enzyme which goes on to activate intracellular secondary messengers like cyclic AMP

Answer 17

beta subunit

Question 18

Receptor protein Tyrosine Kinases phosphorylate ??? and there are two types

Answer 18

specific tyrosine residues on proteins which signals secondary messengers

Question 19

receptor protein kinases are activated directly by ??? and membrane-bound ligands such as ephrins

Answer 19

Extracellular ligands such as growth factors (eg: EGF) and metabolic regulators (eg: insulin)

Question 20

Signal transduction using RTKs usually is terminated by ???

Answer 20

receptor internalisation

Question 21

Activation of receptor tyrosine kinases requires receptor dimerisation which is either ligand or receptor-mediated. Dimerisation causes ???

Answer 21

trans-autophosphorylation

Question 22

Sites of trans-autophosphorylation on RTKs provide binding sites for various cellular signalling proteins which contain two types of domains that recognise phosphorylated tyrosine residues:
* Src-homology 2 (SH2) domains
* ??? domains

Answer 22

phosphotyrosine-binding (PTB)

Question 23

Step 1 of RTK signal transduction cascade: ??? binds to RTK and trans-autophosphorylation occurs

Answer 23

Growth Factor

Question 24

Step 2 of RTK signal transduction cascade: Ras is activated with the GDP bound to Ras turning to GTP. This goes on to phosphorylate ??? and MAPK cascade occurs

Answer 24

Raf

Question 25

Step 3 of RTK signal transduction cascade: after MAPK cascade, ??? factors are activated

Answer 25

Transcription

Question 26

Step 4 of RTK signal transduction cascade: receptors are ??? This terminates the response

Answer 26

internalised and (in most cases) degraded by lysosomes

Question 27

Second messengers are small, ??? soluble intracellular molecules
that stimulate a variety of cellular activities and are very fast

Answer 27

lipid and water

Question 28

What is the amplification step and spreading of signal in signal transduction?

Answer 28

the secondary messengers such as calcium and cAMP

Question 29

??? is produced by adenyl cyclase in response to a wide array of first
messengers and exerts the majority of its effects by activating protein kinase A (PKA)

Answer 29

cAMP

Question 30

phosphotases ACTIVATE or INACTIVATE cAMP?

Answer 30

inactivate

Question 31

calcium can increase cytosolic
calcium 10-100x in response to a variety of first messengers, release
from intracellular stores (ER) or ???

Answer 31

calcium influx from the extracellular environment

Question 32

TRUE or FALSE calcium acts alongside calmodulin. This complex can bind various targets (eg: plasma membrane calcium pump, CaM-kinases) causing effector functions

Answer 32

TRUE

Question 33

Calcium levels are low in the cytosol because it is ??? and the membrane is highly impermeable to the ion. Calcium channels can be transiently opened by action potential or calcium itself.

Answer 33

pumped out into the extracellular space