M&R - Control Of Calcium

Question 0

What is the value for calcium concentration at rest

Intracellularly and extracellularly

Answer 0

Intracellular - 100nM
Extracellular - 1-2mM
(Large inward gradient)

Question 1

Why is calcium control important?

Answer 1

Calcium is needed for many processes, including fertilisation, secretion, neurotransmission, metabolism, muscle contraction, apoptosis and necrosis.

Question 2

What does the calcium gradient rely on?

Answer 2

1. Impermeability of the plasma membrane
2. Ability to expel calcium across the plasma membrane
3. Calcium buffers
4. Intracellular stores

Question 3

How is membrane impermeability regulated?

Answer 3

By the opening and closing of ion channels

Question 4

How is calcium expelled from the cell?

Answer 4

Calcium - ATPase

NCX

Question 5

What are the 2 intracellular stores of calcium?

Answer 5

The sarcoplasmic reticulum and the mitochondria

Question 6

What are the three ways to raise intracellular calcium?

Answer 6

1. Ca2+ influx across the membrane
2. Ca2+ release from rapid release stores
3. Ca2+ release from non rapid release stores

Question 7

What two ways can calcium enter across the plasma membrane?

Answer 7

Voltage gated Ca2+ channels (in response to membrane depolarisation)
Receptor operated Ca2+ channels (in response to a ligand)

Question 8

What is the rapid release store of calcium?

Answer 8

Sarcoplasmic reticulum

Question 9

What 2 ways is calcium released from the SR.?

Answer 9

G protein coupled receptors - ligand binds to GPCR on cell membrane activating the Ga subunit. This realises IP3 which in turn binds to the SR to allow calcium release
Calcium induced calcium release - Ca2+ binds to ryanodine receptor on side of SR -> release of calcium

Question 10

What is the non rapid release calcium store?

Answer 10

The mitochondria