calcium signaling

Question 1

Cytoplasmic Ca2+ buffers are proteins that bind to

Answer 1

free Ca2+ in the cell.

Question 2

cytoplasmic Ca2+ protein buffers function to

Answer 2

restrict the spatial spread of free Ca2+ in order to localize calcium and control signaling pathways that depend upon calcium concentrations.

Question 3

Buffers also store:

Answer 3

Ca2+ until it can be properly transported

Question 4

After calcium ions are released from their effectors, buffers sequester them until they are

Answer 4

transported out of the cell, which is a relatively slow process.

Question 5

Calcium ions are released from the ER/SR into the cytoplasm through

Answer 5

calcium channels mediated by ryanodine and inositol triphosphated (IP3) receptors.

Question 6

Recognition of Ca2+ in the cytoplasm by _____ receptors triggers the ____.

Answer 6

ryanodine

release of Ca2+ from the ER/SR

This is a positive feedback mechanism:

Question 7

the release of calcium ions is sensed by the receptors, leading to _____.

Answer 7

further calcium release

Question 8

IP3 receptors respond to

Answer 8

IP3 (a secondary messenger in a G-coupled protein receptor signaling pathway) to activate Ca2+ channels and stimulate Ca2+ influx into the cytoplasm from the ER/SR.

Question 9

Calcium ions are extruded from cytoplasm into the extracellular space or the lumen of the ER/SR

Answer 9

by Ca2+ pumps that hydrolyze ATP.

Question 10

Ca2+ pump is called:

• In cell membrane:
• In the SR/ER:

Answer 10

Plasma Membrane Ca2+ ATPase (PMCa ATPase)

Sarco/Endoplamic Reticulum Ca2+ ATPase
(SERCa ATPase).

Question 11

EF hands and C2 domains are _____.

Answer 11

structural motifs that depend on coordination with calcium ions

Question 12

EF hand structure:

Answer 12

EF hands are helix-loop-helix domains with two perpendicular alpha helices connected by a short loop that coordinates with calcium ions.

Question 13

Calmodulin is a protein made up of

Answer 13

4 EF hands

Question 14

C2 domains are

Answer 14

structural domains on proteins that target the protein to the cell membrane.

Question 15

______ has a C2 domain.

Answer 15

Protein Kinase A

Question 16

The C2 domain coordinates with

Answer 16

2 or 3 calcium ions.

Question 17

Other calcium ion effectors have

Answer 17

EF-hand domains and many other proteins that bind with plasma membranes contain C2 domains (such as synaptotagmin ,which is involved in neurotransmitter release).

Question 18

synaptotagmin is involved in

Answer 18

neurotransmitter release

Question 19

Fundamentals governing calcium as a cell signal

Answer 19

1. Sources and Sinks for Calcium
2. Movements in/out of Sources/Sinks
3. Cellular Calcium Buffers
4. Calcium Effectors

Question 20

onset of Ca2+ signals is ____

Answer 20

far more rapid than that of other signals.

Question 21

Movement from sources into cytoplasm

Answer 21

1. Ion Channels
2. Plasma membrane:
3. ER/SR, (nuclear envelope):
4. Mitochondria

Question 22

Movement of sources of Calcium Ion Channels

Answer 22

move passive, electrochemically downhill

Question 23

Movement of sources of Calcium:

Plasma Membrane

Answer 23

1. Voltage- and ligand-gated Ca2+ channels
2. store-operated Ca2+ channels (Orai1).
3. Ca2+ moves from outside cell into cytoplasm

Question 24

Movement of sources of calcium: ER/SR (nuclear envelope):

Answer 24

1. IP3 receptors
2. ryanodine receptors.
3. Ca2+ moves from lumen of ER/SR to cytoplasm

Question 25

Movement of sources of calcium: Mitochondria

Answer 25

1. Mitochondrial uniporter
2. permeability transition pore (MPTP)
3. Direction depends on Ca2+ gradient.
4. MPTP contributes to cell death during stroke and myocardial infarction.

Question 26

Movement from cytoplasm into sinks

Answer 26

1. Transporters (active, against electrochemical gradient)
2. Ca2+ pumps use ATP to move Ca2+ out of cytoplasm into extracellular space (PMCA pumps) or into lumen of ER/SR (SERCA pumps)
3. Na+/Ca2+ exchangers extrude Ca2+ out across plasma membrane or from mitochondria into cytoplasm.

Question 27

NCX exchanges {3 Na+}:{1 Ca2+}, deriving energy from

Answer 27

Na+ gradient.

Question 28

Cytoplasmic buffers restrict the ______ and create _____

Answer 28

spatial spread of Ca2+

distinct signaling domains

Question 29

Effectors

Answer 29

1. Surface Membrane Potential
2. Protein Kinase C
3. Synaptotagmin
4. Calmodulin (multiple downstream targets)

Question 30

Surface Membrane Potential

Answer 30

Ca2+ channels, Ca2+-activated channels

(Neuronal bursting, cardiac pacemaking)

Question 31

Protein Kinase C

Answer 31

(Translocation to the membrane)

Question 32

Synaptotagmin

Answer 32

(Ca2+-dependent fusion of synaptic vesicles)

Question 33

Calmodulin

Answer 33

(multiple downstream targets)

Question 34

Binding of Ca2+ causes C2 domains to

Answer 34

associate with the plasma membrane

Question 35

Calmodulin binds to and confers

Answer 35

Ca2+ regulation to a large number of other proteins, including ion channels, protein kinases and phosphatases, and cyclic nucleotide phosphodiesterases.

Question 36

The EF-hand motif of calmodulin is found in

Answer 36

many other Ca2+ effectors, including parvalbumin (a cellular Ca2+ buffer), calpain (a Ca2+-activated protease) and troponin.

Question 37

There are also many Ca2+-binding motifs that

Answer 37

do not resemble C2 domains or EF hands.

Question 38

sources of calcium:

Answer 38

1. ER/SR
2. extra cellular
3. nuclear envelope
4. mitochondria

Question 39

Transporters calcium Movements are much _____than via ion channels

Answer 39

slower

Question 40

Na+/Ca2+ exchangers (NCX, RetX) function:

Answer 40

extrude Ca2+ out across plasma membrane or from mitochondria into cytoplasm. NCX exchanges {3 Na+}:{1 Ca2+}, deriving energy from Na+ gradient.

Question 41

The cytoplasmic buffers (e.g., parvalbumin) restrict the _______

Answer 41

spatial and temporal spread of Ca2+.

Question 42

The cytoplasmic buffers serve as a ______

Answer 42

temporary storage site for Ca2+ while the relatively slow transport processes are operating.

Question 43

effectors: (4)

Answer 43

An effector is how calcium does something:

1. surface membrane potential
2. protein kinase C
3. synaptotagmin
4. Calmodulin

Question 44

Effector: surface membrane potential

Answer 44

can do this directly:
Ca2+ channels,

Also hyper polarized: Ca2+-activated channels

(Neuronal bursting, cardiac pacemaking)

Question 45

Effector: Protein Kinase C

Answer 45

Activated by calcium or diacylglycerol

Translocation to the membrane

Question 46

Effector: Synaototagmin

Answer 46

Ca2+ dependent fusion of synaptic vesicles

Question 47

Binding of Ca2+ causes C2 domains to

Answer 47

associate with the plasma membrane