Calcium Flashcards
What are the different types of phospholipases and what are the main effects of their products
The main types of phospholipases are PLA, PLC and PLD. PLA cleaves the fatty acid from the glycerol backbone to generate anti-inflammatory molecules such as prostaglandins. PLC cleaves between the glycerol backbone and the phosphate group to generate DAG, activating protein kinase C. PLD produces phosphatidic acid that mobilises calcium, inhibits adenyly cyclase, and activates PLC.
What is calcium induced calcium release?
IP3 binding to IP3-gated calcium channels on the endoplasmic reticulum allows the release of calcium from these stores. Binding of the released calcium to the channels allows further calcium release and emptying of the calcium store.
How is the IP3 signalling terminated?
Some of the IP3 is dephosphorylate by specific phosphatases and some is phosphorylated by IP3 kinase to produce IP4. IP4 promotes filling of the calcium stores.
What mechanisms exist for returning intracellular Ca2+ levels back to resting values following calcium induced calcium release
Calcium is returned to resting levels by the action of calcium pumps. The main pump is the Calcium ATPase that uses the free energy associated with ATP hydrolysis to pump calcium up its concentration gradient either back into the calcium stores such as the ER or mitochondria, or out of the cell. The Na+ Ca2+ antiport exchanges the inward movement of Na+ for the outward movement of Ca+. It has a lower calcium affinity than the Ca2+ ATPase and functions predominantly in nerves and muscles.
What do you conclude from the figure below regarding regulation of CaM Kinase II activity?
Low frequency calcium spikes (A) only cause weak transient activation of CaM kinase II. With higher frequency calcium spikes the CaM kinase remains active for an extend period and the increase in activity summates to form the fully active enzyme.
PLC actvates___
Protein Kinase C via DAG
PLC produces____
phosphatidic acid that moblizes calcium ,inhibits a. cyclase and activates PLC
PLC structure
cut at phosphate: leaves us with diacyglyceral
What terminates Ras activity
GAPS
PLD structure
Looks like PLC but has phosphate group
what does DAG activate?
DAG is a second messenger that activates PKC
Where is DAG found
the plasma membrane
what does IP3 do?
it’s a second messenger that induces Ca2+ release
GNRPS cause _____ and GAPS cause ______
Ras activation, Ras inhibition
Ras activation is short-lived due to…
GAPS, which swap GTP for GDP
