Calcium Signaling

Question 1

cytoplasmic Ca2+ ion buffers

Answer 1

proteins that bind Ca have a crucial role in signaling. Buffers (parvalbumin) restrict spatial and temporal spread of Ca2+ => small, specific signaling prevented. Buffers serve as a temp storage for Ca2+ while the relatively sow transport processes work. In ER/SR lumen, high-capacity low affinity buffers (calsequestrin) bind large amounts of Ca2+ to be stored without generation of a large concentration gradient

Question 2

Ca2+ extracellular routes of entry

Answer 2

large gradient from ECF to cytoplasm => Ca movement into cell can be very rapid. Large electrical gradients drive Ca into cell. Can move in via ion channels, ligand gared channels and store operated cannels

Question 3

Ca2+ routes out of ER/SR into cytoplasm

Answer 3

IP3 receptors and ryanodine receptors (little calcium opens these receptors allowing more influx of Ca) move Ca from cytoplasm to ER. Nuclear envelope also contributes due to close relation to ER/SR

Question 4

Ca2+ removal from cytoplasm

Answer 4

active transport (much slower than ion channels), Ca pumps use ATP => Ca back into ECF or ER/SR. Na/Ca exchangers move Ca across plasma membrane or into mitochondria, get energy from Na gradient (3 Na in/1 Ca out)

Question 5

EF hands

Answer 5

part of proteins (like calmodulin) help bind Ca. This motif is found in many Ca effectors such as parvalbumin, calpain (protease), and troponin

Question 6

C2 domains

Answer 6

bind calcium and phosphoserive, it is why protein kinase C is bound to membrane