Intracellular Signalling Pathway

Question 1

Why are most receptors on the cell surface?

Answer 1

As most extracellular signalling molecules can not pass the plasma membrane

Question 2

What is transduction?

Answer 2

Extracellular queue that causes a response

Question 3

What are the 3 superfamilies of cell surface receptors?

Answer 3

G protein-coupled receptors
Ligand gated ion channels
Receptors with intrinsic enzymatic activity

Question 4

How is a receptor activated?

Answer 4

When its complementary ligand binds

Question 5

What do agonists do?

Answer 5

Bind to a receptors and activate it (stimulates)

Question 6

What do antagonists do?

Answer 6

Bind to a receptor but do not activate it (blocks)

Question 7

What are some examples of agonists?

Answer 7

Salbutamol (anti asthma)

Morphine (analgesia)

Question 8

What are some examples of antagonists?

Answer 8

Propranolol (cardiovascular- hypertension)

Haloperidol (neuroleptics- anti-schizophrenic)

Question 9

What do sensory GPCRs sense?

Answer 9

Light, odours and taste

Question 10

What do GPCRs respond to?

Answer 10

Ions
Neurotransmitters
Peptide and non-peptide hormones
Large glycoproteins

Question 11

What is the common basic structure of GPCR’s

Answer 11

Single polypeptide chain, 7 transmembrane regions, extracellular N terminal and intracellular C terminal

Question 12

What areas of the GPCR can be responsible for ligand binding?

Answer 12

2-3 of the transmembrane domains

Or the N terminal region

Question 13

What happens when a ligand binds to a GPCR?

Answer 13

Changes the conformational shape of the receptor
changes shape of GPCR
interacts with a G protein
G protein activated causing GTP to exchange for GDP on the alpha subunit
G protein dissociates into Alpha and GDP and also beta and gamma these then interact with effector
GTP reforms to GDP and subunits reform

Question 14

How many G proteins does GPCR activate?

Answer 14

A single or small population of G proteins

Question 15

How many different G proteins are there?

Answer 15

1000s

Question 16

What does QISS QIQ mean?

Answer 16

Q -Alpha 1 - Phospholipase C
I- Alpha 2 - Inhibits Adenyl cyclase 
S- Beta 1 - Stimulates Adenyl Cyclase
S- Beta 2- Stimulates Adenyl cyclase 
Q- M1- Phospholipase C
I- M2- Inhibits Adenyl cyclase 
Q- M3- Phospholipase C

Question 17

How do Cholera and Pertussis toxin work?

Answer 17

Binds to the cell and enzyme is injected into the cell

Question 18

What does PTx do?

Answer 18

Stops GTP- GDP

Question 19

What does CTx do?

Answer 19

Stops GTPase

Question 20

Where is most of calcium found intracellular or extracellular?

Answer 20

extracellular

Question 21

How are increases in the cytoplasmic ca concentrations mediated?

Answer 21

Movement of Ca across the plasma membrane and release Ca from the ER

Question 22

How are increases in the cytoplasmic ca concentrations opposed?

Answer 22

Relative impermeability of the plasma membrane to Ca
Pumps and transporters that of ca out of the cytoplasm
Ca buffer proteins

Question 23

What is the PMCA?

Answer 23

Plasma membrane Ca- ATPase

Moves Ca out of the cell

Question 24

What is SERCA?

Answer 24

SR/ER Ca-ATPase

Move Ca into the SR/ER

Question 25

What is the NCX?

Answer 25

Na Ca exchanger | Moves Ca out of the cell and Na in- can be reversed

Question 26

What is VOCC?

Answer 26

Voltage operated Ca Channel | Moves Ca into cytoplasm

Question 27

What is LGIC?

Answer 27

Ligand gated ion channel | Moves Ca into cytoplasm

Question 28

What is CICR?

Answer 28

Calcium induced calcium release

Question 29

What is the IP3R?

Answer 29

Inositol 1,4,5- triphosphate receptors | Moves Ca out of ER into cytoplasm

Question 30

What does phospholipase C do?

Answer 30

catalyses the cleavage of the membrane phospholipid PIP2 into IP3 and DAG (second messengers)

Question 31

What is signal amplification?

Answer 31

A few molecules of binding to a cell surface ay cause a massive cellular response e.g. adenylyl cyclase- cyclic AMP to PKA

Question 32

What hormones increase the force of contraction in the heart?

Answer 32

Adrenaline and Noradrenaline by binding to ventricular B1 adrenoreceptors

Question 33

What hormone can cause vasoconstriction?

Answer 33

Noradrenaline by binding to a1 adrenoreceptors of vascular smooth muscle

Question 34

What hormone can cause bronchoconstriction?

Answer 34

Acetylcholine by binding to M3 muscarinic receptors of bronchiole smooth muscle

Question 35

What modulates neurotransmitter release?

Answer 35

presynaptic G protein coupled receptors

Question 36

What can G proteins inhibit?

Answer 36

specific types of voltage operated Ca2+ channels (VOCCs) reducing Ca influx and neurotransmitter release

Question 37

What is the summary of GCPRs?

Answer 37

Diversity, Specificity, Amplification