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BIO 142 > Cell Signaling > Flashcards

Cell Signaling Flashcards

1
Q

Are all hormones hydrophobic?

A

no

some like peptide-hormones are hydrophilic and have a hard time passing the cell membrane

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2
Q

Signal transduction

A

any process by which a cell converts one kind of signal or stimulus into another

sequence of linked reactions by enzymes within the cell

accomplished through secondary messengers

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3
Q

Secondary messengers

A

molecules that relay signals received at receptors on the cell surface to target molecules in the cytosol/nucleus

amplify the strength of the signal

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4
Q

Example of signal amplification

A

lots of cAMP secondary molecules are created through one ligand molecule of epinephrine

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5
Q

Categories of secondary messengers

A

cyclic nucleotides (ex: cAMP), ions, and lipids

anything but proteins

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6
Q

Two classes of extracellular molecules? Which one is larger class?

A
  1. Intracellular receptors

2. Extracellular receptors (larger class)

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7
Q

What types of extracellular molecules trigger intracellular receptors?

A

small and hydrophobic molecules can move through the plasma membrane

ex: steroid hormones (cortisol) and nitric oxide

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8
Q

What types of extracellular molecules trigger extracellular receptors?

A

signals that are too hydrophilic to cross the plasma membrane

ex: insulin

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9
Q

What controls blood pressure?

A

degree of contraction of smooth muscle is important for blood flow and controls BP

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10
Q

What types of cells line every blood vessel?

A

endothelial cells

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11
Q

Where is nitric oxide produced?

A

endothelial cells from arginine

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12
Q

What does NO trigger?

A

moves from endothelial cells to smooth muscle and activates guanylyl cyclase

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13
Q

Guanylyl cyclase

A

stimulates formation of cGMP which triggers relaxation of smooth muscle

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14
Q

Phosphodiesterase

A

PDE

within smooth muscle tissues, breaks down cGMP and causes the smooth muscle to constrict

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15
Q

Viagra

A

inhibits PDE and results in prolonged cGMP signaling and prolonged relaxation

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16
Q

Steroid hormones

A

hydrophobic hormones that bind to receptors in the cytoplasm or nucleus

these complexes then act as promoting factor to regulate gene transcription

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17
Q

Cortisol example

A

example of a steroid hormone that forms a complex that supresses the immune system

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18
Q

3 types of extracellular receptor models

A

G-protein linked receptors

Ion-channel linked receptors

Enzyme linked receptors

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19
Q

G-protein linked receptors overview

A

several different types of G-proteins that each bind a specific type of receptor and set of downstream targets

all G-proteins have alpha, beta, gamma subunits and operate similarly

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20
Q

What is the largest family of extracellular receptor models?

A

g-protein linked receptors

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21
Q

trimeric G-proteins

A

alpha, beta, gamma subunits of g-protein

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22
Q

Inactive G-proteins

A

bound by GDP at the alpha-subunit

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23
Q

What happens when a hydrophilic signal binds to the extracellular receptor?

A

shape change on the cytoplasmic side of the membrane that allows a g-protein to bind to the receptor

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24
Q

What happens when a g-protein binds to the receptor?

A

alpha-subunit swaps GDP nucleotide to GTP to activate the g-protein

25
Q

Does the alpha-subunit catalyze the swap of GDP to GTP?

A

NO

26
Q

What happens when the g-protein is activated?

A

alpha subunit can detatch from beta and gamma subunits

g-protein can move around the cell and roam plasma membrane

activated alpha and beta-gamma subunits can interact directly with target proteins in the plasma membrane to trigger amplification

27
Q

How do alpha and beta-gamma subunits become unactivated?

A

alpha-subunit hydrolyses the bound GTP to GDP

alpha subunit rejoins with the beta-gamma subunit and becomes inactive

28
Q

Cholera

A

caused by inability to hydolysize GTP to GDP

*review how to treat this on a molecular level

29
Q

What does Gs type of g-protein activate?

A

Adenylyl cyclase

30
Q

Adenylyl cyclase

A

catalyzes cAMP formation

31
Q

cAMP

A

secondary messenger that activates the enzyme Protein Kinase A

PKA phosphorylates specific gene transcription facts which then trigger specific gene expression

32
Q

What degrades cAMP?

A

phosphodiesterase

caffeine inhibits phosphodiesterase

33
Q

What does Gq type of g-protein activate?

A

Phospholipase C

activates through phosphylation from the alpha-subunit

34
Q

Phospholipase C

A

hydrolyses phospholipid, PIP2 into IP3 and DAG

DAG = lipid tails
IP3=soluble sugar

35
Q

DAG

A

comes from hydrolysis of PIP2

secondary messenger that moves around plasma membrane

DAG works with calcium to activate PKC

36
Q

IP3

A

comes from hydrolysis of PIP2

moves into cystoplasm, since soluble, and binds to calcium channels on the smooth ER

37
Q

Why are calcium channels on the smooth ER?

A

calcium deposits are stored there

38
Q

What happens when IP3 binds to calcium channels?

A

the channels allow calcium to diffuse from the smooth ER to the cytoplasm

39
Q

Calcium

A

once released from the smooth ER, acts as a secondary messenger with DAG to activate PKC

40
Q

Ion-channel linked receptors

A

convert chemical signals into electrical signals

can be opened to let certain ions in or out of a cell and are responsible for rapid transmission of signals across synapses in the nervous system

41
Q

example of ion-channel linked receptors

A

Acetylcholine is a neurotransmitter that opens up acetylcholine receptor to Na+ ions

makes the inside of cell have positive charge

42
Q

example of enzyme linked receptor

A

Epidermal Growth Factor Receptor (EGFR)

43
Q

What happens when EGF signal molecule binds to EGFR?

A

it triggers dimerization

44
Q

what happens once receptors are dimerized?

A

Tyrosin Kinase phosphylates attached tyrosines on the cytosolic tail

45
Q

Why is the phosphorylation of EGFR trans-?

A

left-hand kinase phosphorylates right-hand tyrosines and vice versa

46
Q

What binds to the phospho-tyrosine residues?

A

downstream cytoplasmic proteins

47
Q

What do downstream cytoplasmic proteins do?

A

build a bridge between the receptor tyrosine kinase (RTK) and the Ras protein, which is subsequently activated

48
Q

Ras protein

A

small protein bound by a lipid tail to the internal plasma membrane

RAS protein is a single subunit GTP-binding protein

Ras protein activates a phosphorylation cascade in which a series of protein kinases phosphorylate and activate one another (MAPKKK -> MAPK)

49
Q

How is the Ras protein activated?

A

by exchange of GDP to GTP

50
Q

What is the last protein that the Ras- protein stimulates?

A

MAP-kinase

51
Q

MAP kinase

A

phosphorylates regulatory proteins on serine and theronine

leads to growth (epidermal GROWTH factor receptor)

52
Q

Mutant Ras proteins

A

unable to dissociate GTP and are always activated

leads to cancer because promotes unregulated growth

53
Q

what is meant by the term “always on?”

A

indicates that an enzyme is on regardless of what is happening before it

for example, it can bypass phosphorylzation step

means that to reduce its effects you have to turn off DOWNSTREAM constituents

54
Q

Are signaling pathways independent of one another?

A

No

there is often crosstalk between pathways

55
Q

How is cell response to extracellular signals determined?

A

Determined by the total number of signals that the cell can interpret

56
Q

autrocrine

A

self signaling

57
Q

juxtacrine

A

signaling touching cells

58
Q

paracrine

A

signaling nearby cells

59
Q

endocrine

A

signaling cells far away through the bloodstream

BIO 142 (14 decks)

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