Control of Intacellular Calcium Flashcards Preview

ESA 2- Membranes and Receptors > Control of Intacellular Calcium > Flashcards

Flashcards in Control of Intacellular Calcium Deck (51):
1

Give 8 examples of cellular processes that are calcium sensitive

Fertilisation, Secretion, Neurotransmission, Metabolism, Contraction, Learning and memory, Apoptosis, Necrosis

2

How can Ca be metabolised?

It can’t

3

How does the cell regulate intracellular Ca concentration?

Based largely on moving Ca into and out of the cytoplasm

4

What is the extracellular concentration of Ca at rest

1-2mM

5

What is the intracellular concentration of Ca at rest?

100nM

6

What is the problem with the tight regulation of Ca levels?

The large gradient is energy expensive

7

What are the advantages of the large Ca gradient?

Changes in intracellular Ca occur rapidly and with little movement

8

What are the disadvantages of the large Ca gradient?

Ca overload leads to loss of regulation and cell death

9

What does the Ca gradient rely on?

The relative impermeability of the plasma membrane 
The ability to expel Ca across the plasma membrane
Ca buffers 
Intracellular Ca stores

10

What gives the ability to expel Ca across the plasma membrane?

Ca ATPase
Na-Ca Exchanger

11

What are the types of intracellular Ca stores?

Rapidly releasable 
Non-rapidly releasable

12

What is membrane permeability regulated by?

The open/closed state of ion channels

13

What is the affinity of Ca ATPase?

High

14

What is the capacity of Ca ATPase?

Low

15

How does Ca ATPase work?

Intracellular Ca increases
Ca binds to calmodulin- a binding trigger protein 
Calmodulin-Ca binds to Ca ATPase
Ca is removed from cell

16

What is the affinity of the Na/Ca Exchanger?

Low

17

What is the capacity of the Na/Ca Exchanger?

High

18

What is required to drive the Na/Ca Exchanger?

The Na gradient produced by Na/K-ATPase

19

How many Na are transported for how many Ca in the Na/Ca Exchanger?

3 Na in for 1 Ca out

20

What does the Na/Ca Exchanger do for the charge of the membrane?

Nothing- the antiporter is electrogenic

21

When does the Na/Ca Exchanger work best?

At resting membrane potential

22

What do Ca buffers do?

Limit diffusion

23

How do Ca buffers limit diffusion?

Through ATP and Ca binding proteins

24

Give 4 examples of Ca binding proteins

Parvalbumin 
Calreticulin 
Calbindin
Calsequestin

25

What does diffusion of Ca depend on?

The concentration of binding molecules, and their level of saturation

26

What happens when some other proteins bind Ca?

It alters their function

27

Give an example of a protein that changes function on Ca binding

Calmodulin

28

How high can Ca levels rise when it is being used to regulate cellular activity?

~1µm

29

How is intracellular Ca concentration increased?

Ca influx across the plasma membrane due to altered permeability 
Ca release from ‘rapidly releasable’ and ‘non-rapidly releasable’ stores

30

How does the permeability of the membrane allowing Ca influx change?

Voltage gated Ca channels
Receptor operation ion channels (ionotropic receptors)

31

What controls Ca release from rapidly releasable stores?

G-protein coupled receptors
Ca induced Ca release

32

What are voltage-gated calcium channels?

Channels that open to allow the influx of calcium down its concentration gradient, triggered by membrane depolarisation

33

How does a receptor operated Ca channel work?

A ligand/agonist binds to the channel, opening it and allowing Ca to enter down its concentration gradient

34

Where are stores of Ca set up inside the cell?

In the sarco/endoplasmic reticulum

35

How are Ca stores set up in the sarco/endoplasmic reticulum set up?

By the SERCA protein. 
Ca moved in using energy from ATP hydrolysis

36

What happens once Ca has been moved into the sarco/endoplasmic reticulum?

It binds to proteins such as calsequestrin

37

How do G-protein coupled receptors alter intracellular Ca concentration?

A ligand binds to the GPCR on the cell membrane, activating its Gαq subunit. This subunit then binds to the membrane phospholipid PIP2, releasing IP3, which in turn binds to its receptor on the sarco/endoplasmic reticulum, triggering the release of Ca down its concentration gradient into the cell

38

How does Ca induced Ca release (CICR) work?

Ca binds to the Ryanodine receptor on the side of the sarco/endoplasmic reticulum, triggering the release of calcium down its concentration into the cell

39

Give an example of an important physiological role for CICR?

In the cardiac myocyte

40

Why is CICR important in the cardiac myocyte?

Ca entry through VOCCs following depolarisation of the membrane binds to the ryanodine receptors, causing an explosive release of large amounts of Ca from intracellular stores

41

What are mitochondria important, regarding calcium?

They take up Ca when intracellular concentrations are high as a protective mechanism 
Participate in normal Ca signalling

42

Why can mitochondria take place in normal Ca signalling?

Due to microdomains

43

What are microdomains?

Areas of cytoplasm with higher concentration of Ca due to their proximity to a channel

44

What is the purpose of mitochondria taking up Ca?

Aids in buffering, regulating, signalling, and stimulation of ATP production

45

How do mitochondria take up Ca?

Via a Ca uniporter

46

What drives the Ca uniporter in mitochondria?

Respiration

47

What does repetitive signalling require?

A return to the basal state

48

What happens if there is too much Ca for too long?

It’s toxic to cell

49

What does a return to basal Ca require?

Termination of signal 
Ca removal 
Ca store refilling

50

How are Ca stores refilled?

By recycling of cytosolic Ca 
Using Ca stored in mitochondria to replenish SR stores

51

How does the Ca stored in mitochondria replenish the SR stores?

Via the store-operated Ca channel (SOC)