lecture 18

Question 1

elementary events

Answer 1

highly localised

Question 2

a calcium puff is

Answer 2

an elementary event from a cluster of IP3 receptors

Question 3

calcium release from a cluster of about 10 ryanodine receptors is a

Answer 3

calcium spark

Question 4

intermediate level of hormone activating the cell, generating an intermediate level of IP3, IP3 is sensitising the IP3 receptors so you get a calcium puff

Answer 4

if you increase the hormone concentration you increase the amount of IP3 produced in the cells, increases the activation of the neighbouring clusters of IP3 receptors and they will release calcium CICR. the wave will propagate across the cell
if you have a signal between intermediate and high you get an abortive wave
smaller event than elementary is called a fundamental event - calcium release from just one receptor (blip - IP3, quark - RyRs)
global events - waves

Question 5

cluster of RyRs on the ER, releases its calcium spark very closely to the calcium activated potassium channel

Answer 5

if the calcium spark is right in the mouth of the channel it will activate it
potassium ions will leave the cells down their concentration gradient, the cell is hyperpolarised meaning the muscle will relax

Question 6

if you have a global calcium signal in the muscle cells the muscle will contract

Answer 6

spark = relaxation
wave = contraction
in cardiac myocyte

Question 7

monolayer of endothelial cells line the trachea
endothelial cells have cilia on them that beat to remove foreign particles
ciliary beating becomes co-ordinated by calcium wave

Answer 7

cells have gap junctions so cytosols of the cells are essentially continuous
IP3 or calcium ions move through the gap junctions to propagate the waves between the cells

Question 8

example of ca signal physiological reponse

Answer 8

glycogen breakdown in the liver

Question 9

calcium will bind to its sensing protein in the liver cell (calmodulin)
calcium calmodulin binds to and activates its effector protein (calcium calmodulin dependent protein kinase II)
Ca.CaM Kinase II phosphorylates its substrate protein which is called phosphorylase kinase (using ATP)
when phosphorylase kinase is phosphorylated it becomes activated and it phosphorylates its target protein which is phosphorylase (using ATP)
activated phosphorylase converts glycogen to glucose

Answer 9

activating solution containing calcium, calmodulin and ATP. To mimic the upstroke of the calcium spike
to mimic the downstroke of the spike they poured down the column a deactivating solution which contained EGTA (binds to calcium ions and they’re essentially removed from calcium calmodulin complex)

Question 10

kinase II enzyme spends more time in its active form when the frequency of spikes is greater