BIOL1025 - Signalling pathways induced in cells (2)

Question 1

lipophilic signalling

Answer 1

receptors inside cell

Question 2

examples of lipophilic signalling

Answer 2

NO, steroids and thyroxin

Question 3

NO

Answer 3

non-polar - local mediator - cant’ be stored
only trigger response with NO receptor
from arginine
uses NO synthase - eNOS, iNOS, nNOS

Question 4

why NO is local

Answer 4

have very short half life

diffuses to adjacent cell

Question 5

eNOS - function

Answer 5

control diameter of vessel and pressure

stimulated by histamine, acetyl choline, increase cheer flow

Question 6

eNOS result

Answer 6

NO diffuses into smooth muscle cells = relaxation to decrease blood pressure

Question 7

eNOS

Answer 7

blood vessel endothelial cell

Question 8

nNOS

Answer 8

neuronal cells

Question 9

iNOS

Answer 9

inducible isoform occurring in immune cells

Question 10

Guanylate cyclase

Answer 10

target NO and binds to activate

cGMP produced from GTP

Question 11

Pk

Answer 11

protein kinase

Question 12

eNOS process

Answer 12

binds to Pk G - phosphorylate Ca2+ channels to block it

decreasing intracellular [Ca2+] = inhibit myosin-actin interaction

Question 13

phosphorylation of K+ channel

Answer 13

activates it

hyperpolarise and relaxes as K+ leaks

Question 14

phosphorylation of myosin light chain

Answer 14

actives causing the smooth muscles to relax

Question 15

stopping NO signalling

Answer 15

rapidly oxidised by spontaneous breakdown
cGMP convert to GMP by phosphodiesterase (11 isoform) - breaks phosphodiesterase bond with 3’OH ribose
dephosphorylates protein back to OG form by phosphatase

Question 16

steroid signalling

Answer 16

HP hormones act as endocrine signal
synthesised from cholesterol and releases on demand into blood and to tissues
carried by protein to transport to every cell but bind to specific receptors

Question 17

steroid signalling function

Answer 17

undergo conformational changes - unmasking DNA binding sites and nuclear localisation site on receptor
transported to nuclease - DNA binding by receptor regulations gene expression

Question 18

thyroxine signalling

Answer 18

can’t cross cell membrane - has transporters to go into cell - diffuse into nucleus
acts similar to steroids but receptors are already in nucleus

Question 19

how signals are removed in steroid signalling

Answer 19

by metabolism of steroids

Question 20

hydrophilic signalling

Answer 20

cannot penetrate cell membrane therefore require transmembrane proteins as receptors

Question 21

3 major classes of receptors of hydrophilic signalling

Answer 21

ligand gated ion channels
G-protein linked receptors
Enzyme linked receptors