Signal Transduction

Question 1

True or False:

Protein kinases transfer phosphates from ATP to protein, a process called phosphorylation

Answer 1

True

Question 2

True or False:

Phosphorylation most commonly occurs on serine, threonine, or tyrosine residues AND normally leads to protein activation

Answer 2

True

Question 3

True or False:

ATP is a limiting factor for how many pathways you can have going on in a cell.

Answer 3

True

Since ATP is a source of phosphate for phosphorylation, which is used to activate proteins

Question 4

What do protein phosphatases do?

Answer 4

Remove phosphates from proteins - dephosphorylation

Question 5

True or False:

Second messengers are big, non-protein, water soluble molecules that are already in the cells.

Answer 5

False

Second messengers are SMALL, non-protein, water soluble molecules OR IONS that are already in the cells.

Question 6

Name two common second messengers

Answer 6

Cyclic AMP (cAMP) and calcium ions

Question 7

What enzyme breaks cAMP down to its inactive form, AMP?

Answer 7

Phosphodiesterase

Question 8

What enzyme converts ATP to cAMP in response to an extracellular signal?

Answer 8

Adenylyl cyclase

Question 9

Fill in the gaps:
The toxin produced by the cholera bacteria permanently activates a ______ involved in regulating ____ and ____ excretion.

Answer 9

The toxin produced by the cholera bacteria permanently activates a G-protein involved in regulating salt and water excretion.

Question 10

Fill in the gaps:

Calcium ions are stored in the _____ or _____ instead of the cytosol so they can be used as a second messenger.

Answer 10

Calcium ions are stored in the ER or mitochondria instead of the cytosol so they can be used as a second messenger.

Question 11

True or False:

Under normal conditions intracellular calcium concentration is very high

Answer 11

False
Under normal conditions intracellular calcium concentration is very LOW
(approx. 10,000 times lower than in blood stream)

Question 12

True or False:

Under normal conditions intracellular calcium concentration is very low

Answer 12

True

approx. 10,000 times lower than in blood stream

Question 13

Fill in the gaps:

Pathways leading to the release of calcium involve _____ and_____ as additional second messengers

Answer 13

Pathways leading to the release of calcium involve inositol triphosphate (IP3) and diacylglycerol (DAG) as additional second messengers

Question 14

Fill in the gaps:
Activation of ________ leads to cleavage of membrane phospholipid ____ into ____ and ___

____ diffuses through cytosol to its gated ______ channel in ER membrane & causes it to open

_____ ions flow out (down concentration gradient) raising cytoplasmic ____ levels

These _____ ions activate next protein in one (or more) signalling pathways

Answer 14

Activation of phospholipase C leads to cleavage of membrane phospholipid (PIP2) into DAG and IP3

IP3 diffuses through cytosol to an IP3 gated calcium channel in ER membrane & causes it to open

Calcium ions flow out (down concentration gradient) raising cytoplasmic calcium levels

Calcium ions activate next protein in one (or more) signalling pathways

Question 15

Explain the negative feedback loop for calcium ions involving CaM

Answer 15

Calcium ions bind to Calmodulin (CaM), inducing a conformational change, allowing CaM to activate and inactivate other proteins.

Ca2+ATPase activated, which pumps calcium ions out of cell, reducing cytoplasmic calcium concentration.

Question 16

Other than Ca2+ATPase, what other proteins does activated Calmodulin (CaM) affect?

Answer 16

Protein kinases and phosphatases

Adenyly cyclases and phosphodiesterases (cAMP formation/breakdown)

Question 17

What is the purpose of scaffolding proteins

Answer 17

Making sure relevant proteins and messengers are close enough for pathway to be fast and efficient