PSC2002/L17 Calcium Signalling I

Question 1

Give 3 responses from a target cell once delivered a chemical signal.

Answer 1

Secretion
Metabolism
Contraction
Cell growth
Excitability

Question 2

Give the 5 signal reception and processing pathways.

Answer 2

Steroid hormones
Ligand-gated ion channels/receptor-operated channels
Cyclic AMP pathway
Phosphoinositide pathway
Tyrosine kinase pathway

Question 3

What kind of molecule is IP3?

Answer 3

A group of lipids

Question 4

Describe the calcium wave that is formed from a fertilised egg. (3)

Answer 4

Fertilisation envelope formed from the exocytotic secretion from point of fertilisation (made of proteins from egg)
Forms physical barrier and prevents polysperming
Triggers exocytotic secretion & sets developmental process

Question 5

State the 4 off mechanisms of Ca2+ in cells.

Answer 5

Ca-ATPase pumps (PMCA, SERCA)
Na/Ca exchanger
Mitochondria (& other organelles)
Proteins (&lipids), buffers (parvalbumin), sensors (calmodulin)

Question 6

Describe the role of Ca-ATPase pumps.

Answer 6

Actively transport Ca2+ into/out of ER (SERCA) and cells (PMCA)

Question 7

Describe the role of Na/Ca exchangers.

Answer 7

Na+ into cell and Ca2+ out of cell or vice versa depending on conc. gradient (3:1 Na:Ca)

Question 8

Describe how mitochondria keep [Ca2+] low in cells.

Answer 8

Calcium uptake & buffering
Calcium release under controlled conditions
Via MCU (mitochondrial calcium uniporter)

Question 9

How do buffers keep calcium levels in cells low?

Answer 9

Buffers act like a sponge -soak up Ca2+
Sensors detect change in [Ca2+] and activate downstream response

Question 10

Why is [Ca2+] in cells cytotoxic?

Answer 10

Forms large precipitates in cells
Ca2+ insoluble and builds up

Question 11

Describe the Ca2+ gradient between ER, cytoplasm and outside the cell.

Answer 11

Ca2+ from outside into cell
Ca2+ from ER into cytoplasm

Question 12

What activates RyR? (2)

Answer 12

Ryanodine
Voltage

Question 13

Briefly summarise ON and OFF mechanisms of Ca2+ signalling.

Answer 13

ON mechanisms involve entry of Ca2+ through ion channels or release from intracellular stores
OFF mechanisms remove or sequester calcium from cytoplasm through pumps, exchangers and storage

Question 14

What are the 3 types of Ca2+ signal?

Answer 14

Elementary events
Global Ca2+ wave (intracellular)
Global Ca2+ wave (intercellular)

Question 15

Describe the role of phospholipase C-beta.

Answer 15

PIP2 bound to membrane phospholipids
Amplifier cleaves PIP2, releases IP3 into cytoplasm with DAG still attached

Question 16

What is the difference between the tris and tri prefix?

Answer 16

Tris - 3 phosphates on different carbons
Tri - 3 phosphates as chain on same carbon