communication between cells

Question 1

stages of ionotropic receptor signal transduction

Answer 1

ligand binds to receptor protein → change in conformation of channel protein → pore opens → pore allows ions to diffuse in or out according to conc. gradient

Question 2

what is the nicotinic acetylcholine receptor involved in

Answer 2

muscular contraction in skeletal muscle

Question 3

what is the GABAa receptor involved in

Answer 3

decreasing neuronal excitability in neurones

Question 4

examples of secondary messengers

Answer 4

IP3, G-protein

Question 5

how many transmembrane sections of a G-protein are there

Answer 5

7

Question 6

what are the heterotimers of a G-protein

Answer 6

a, B and y

Question 7

stages of G-protein linked receptor signal transduction

Answer 7

7-TM receptor and IC heterotrimeric G-protein (a, B and y; B and y are always bound together) are inactive → ligand binding to 7-TM changes conformation of receptor → unassociated G-protein binds to receptor as less energy required following conformational change → bound GDP molecule is exchanged for GTP, providing energy for a-subunit to dissociate from B-y-subunit → a-subunit binds to target proteins → internal GTPase activity on a-subunit dephosphorylates GTP to GDP → a-subunit dissociates from target protein, becoming inactive again, and returns to bind to B-y-subunit

Question 8

diagram of G-protein linked receptor signal transduction

Answer 8

diagram from tissues 9

Question 9

what happens to G-protein activation as long as ligand remains bound receptor

Answer 9

any number of G-proteins can become activated

Question 10

what happens to G-protein activation once a ligand has bound

Answer 10

G-protein cannot be activated

Question 11

3 types of G-protein linked receptor

Answer 11

Gs, Gi and Gq

Question 12

what branch of the peripheral nervous system does the Gs protein linked receptor control

Answer 12

sympathetic

Question 13

what does the Gs protein linked receptor stimulate and what does this do

Answer 13

adenyl cyclase; converts ATP to cAMP

Question 14

what does cAMP do

Answer 14

activate protein kinase A (PKA)

Question 15

example of Gs protein linked receptor and function

Answer 15

B1-adrenergic receptor to increase heart rate

Question 16

what branch of the peripheral nervous system does the Gi protein linked receptor control

Answer 16

parasympathetic

Question 17

what does the Gi protein linked receptor inhibit and what is the consequence

Answer 17

adenyl cyclase so reduces protein kinase A (PKA) levels

Question 18

example of Gi protein linked receptor and function

Answer 18

M2-muscarinic receptor to decrease heart rate

Question 19

what does Gq protein linked receptor stimulate

Answer 19

phospholipase C (PLC)

Question 20

what does phospholipase C (PLC) do

Answer 20

converts PIP2 to IP3 and DAG

Question 21

what does IP3 stimulate

Answer 21

Ca2+ release

Question 22

what does DAG activate

Answer 22

protein kinase A (PKA)

Question 23

example of Gq protein linked receptor and function

Answer 23

AT-1 angiotensin receptor to cause vasoconstriction

Question 24

when a ligand binds to an enzyme-linked receptor, what does it cause the receptors to do

Answer 24

cluster

Question 25

why do the receptors cluster

Answer 25

clustering activates enzyme activity within cytoplasmic domain

Question 26

what is the enzyme activity

Answer 26

receptor phosphorylation

Question 27

what happens when the receptors are phosphorylated

Answer 27

binding of signalling proteins to cytoplasmic domain

Question 28

what do these signalling proteins do and what is the outcome

Answer 28

recruit other signalling proteins causing a signal to be generated within cell

Question 29

what are enzyme-linked receptors important for

Answer 29

cell growth and proliferation

Question 30

example of enzyme-linked receptor

Answer 30

tyrosine kinase

Question 31

in tyrosine kinase, what is phosphorylated

Answer 31

tyrosine

Question 32

examples of tyrosine kinase in a receptor and consequences

Answer 32

insulin receptor for glucose uptake; epidermal growth factor, transforming growth factor B (ErbB) for cell growth and proliferation

Question 33

other enzyme-linked receptors

Answer 33

guanylyl-cyclase in NPRA, Ser/Thr-kinase in TBR1

Question 34

what is the function of guanylyl-cyclase in NPRA

Answer 34

vasodilation and decrease blood pressure

Question 35

what is the function of Ser/Thr-kinase in TBR1

Answer 35

apoptosis

Question 36

types of intracellular receptors depending on location

Answer 36

cytoplasmic and nuclear

Question 37

what are cytoplasmic intracellular receptors associated with

Answer 37

chaperone molecules such as heat shock proteins

Question 38

stages of cytoplasmic intracellular receptor signal transduction

Answer 38

hormone binds to receptor → hsp dissociates → 2 hormone bound receptors form a homodimer (clustering) → homodimer translocates to nucleus → binds to DNA (very slow)

Question 39

diagram of cytoplasmic intracellular receptor signal transduction

Answer 39

diagram from tissues 9

Question 40

example of cytoplasmic intracellular receptor

Answer 40

glucocorticoid receptor

Question 41

in the glucocotricoid receptor, what binds and what is the consequence

Answer 41

cortisol and corticosterone bind; decreases immune response and increases gluconeogenesis

Question 42

stages of nuclear intracellular receptor signal transduction

Answer 42

binding of hormone ligand → transcriptional regulation

Question 43

diagram of nuclear intracellular receptor signal transduction

Answer 43

diagram from tissues 9

Question 44

example of nuclear intracellular receptor

Answer 44

thyroid hormone receptor

Question 45

in the thyroid hormone receptor, what binds and what is the consequence

Answer 45

thyroxine (T4) and triiodothyronine (T3) bind; growth and development

Question 46

what can detect changes in Ca2+ concentration when Ca2+ is used as a secondary messenger

Answer 46

proteins e.g. calmodulin, Ca2+-dependent protein kinases

Question 47

4 ways of switching off an intracellular signal

Answer 47

receptor inactivation; receptor down-regulation (i.e. breakdown by lysosomes); production of inhibitory proteins; inactivation of intracellular signalling proteins