Receptors and Cell Signalling

Question 1

What are Type 1 receptors?

Answer 1

Fast neurotransmission directly coupled to an ion channel - ionotropic

Question 2

What are Type 2 receptors?

Answer 2

Signal via G protein pathways - metabotropic

Question 3

What are Type 3 receptors?

Answer 3

Signal via enzyme-linked cell surface receptors

Question 4

What are Type 4 Receptors?

Answer 4

Located in special regions of DNA - promote gene upregulation

Question 5

What are examples of ?

Answer 5

GABA, ACh, 5-HT

Question 6

What is a typical Type 1 receptor?

Answer 6

Nicotonic ACh receptor - 5 membranes with subunits 2a, b, gamma, positro

Question 7

How does ACh depolarise the cell?

Answer 7

2 ACh molecules bind to the 2 alpha units opening ligand gated NA ion channel

Question 8

What is Intracellular signalling

Answer 8

Binding of a ligand with a receptor activates enzyme cascade inducing cellular response

Question 9

What do receptors do?

Answer 9

Provide means of selectively transmitting extracellular signals across the cell membrane enabling cells to respond to stimuli

Question 10

What are some examples of cellular responses?

Answer 10

Opening ion channels, increased secretion, cell motility

Question 11

What are 2 pathways of Intracellular signalling?

Answer 11

Type 2 g protein or Enzyme receptor type 3 pathway

Question 12

What do G protein coupled receptors contain?

Answer 12

Single polypeptide chain forming 7 transmembrane a helices with n-terminus and carboxy terminus

Question 13

How does G-protein couple to receptors?

Answer 13

Ligand binds to a helices in the membrane the 3rd loop of receptor couples to G proteins

Question 14

What are G proteins?

Answer 14

Highly mobile proteins in the membrane with 3 subunits of a b and gamma

Question 15

What does the alpha subunit of gproteins function as ?

Answer 15

GTPase converting GTP to GDP

Question 16

What does the B and gamma subunits function as?

Answer 16

Form a complex very hydrophobic and stay close to membrane, when inactivated GDP binds to a subunit

Question 17

What are the 3 Stages of G Protein activation?

Answer 17

Binding to ligand receptor
A coupled to GTP to target adenylate cyclase
The A hydrolyses GTP into GDP

Question 18

How can G-protein mechanisms amplify signals?

Answer 18

a single receptor can activate several g proteins

Question 19

What are main targets for G proteins?

Answer 19

Adenylate cyclase - cAMP
Guanylate cyclase cGMP
Phosphilpase
Regulate ion channe;s

Question 20

What does Activated andenylate cyclase convert ATP into?

Answer 20

cAMP

Question 21

What does cAMP do?

Answer 21

Function as secondary messenger, specifically targets inactive protein kinases activating them

Question 22

How is cAMP inactivated?

Answer 22

By hydrolysis of phosphodiesterase, inhibited by drugs such as caffeine

Question 23

What is an example of cAMP role?

Answer 23

B adrenoreceptors activated breakdown of glycogen

Question 24

What is the Phospoinositide system based on?

Answer 24

Membrane phospholipid 4,5 and diphosphate

Question 25

What does PIP2 do?

Answer 25

Acts as substrate for membrane bound enzyme DAG and InsP3 (secondary messengers)

Question 26

What dies DAG result in?

Answer 26

Protein kinase C activation

Question 27

What does Insp3 do?

Answer 27

Promotes calcium release from intracellular stores

Question 28

Why is Calcium release in the cytosol important?

Answer 28

Muscle contraction, Control of secretion from exocrine glands, Hormones release

Question 29

What does DAG activate?

Answer 29

PKC

Question 30

What does PKC do?

Answer 30

Muscle contraction, inflammatory response, increase neurotransmitter release

Question 31

What does the Production of Cyclic GMP from ligand do?

Answer 31

Bind to G-kinase acting as secondary messenger

Question 32

What is an example of guanylyl cyclase receptor?

Answer 32

Atrial natiriureitc peptide

Question 33

What are the 4 variants of Type 3 Receptors?

Answer 33

``` Receptor Tyrosine kinases Linked tyrosine kinases Tyrosine phosphatases Serine kinases ```

Question 34

What do Type 4 DNA receptors do?

Answer 34

Wraps around DNA to form target for steroid hormones

Question 35

What does steroid binding to DNA sequence do?

Answer 35

Increase RNA polymerase activity and gene transcription