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Molecular Exam 2 > Cell Communication 1: Signal Transduction > Flashcards

Cell Communication 1: Signal Transduction Flashcards

1
Q

What is signal transduction?

A

extracellular signaling molecules bind to specific receptors in target cells to initiate a chain of events

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2
Q

Why is signal transduction important?

A

cell, tissues, and organs need to communicate in the development of the organism and for coordination of metabolism

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3
Q

What responses do external signals induce?

A

fast response

slow response

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4
Q

What is fast response?

A

change in activity or function of enzymes or proteins in the cell

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5
Q

What is slow response?

A

change in amounts of proteins by change in expression of genes

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6
Q

What is endocrine signaling?

A

long distance signaling
signal-bloodstream-distant target cells
freely diffusible signal

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7
Q

What is paracrine signaling?

A

acts locally

affects cells nearby and short lived signal

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8
Q

What is synaptic signaling?

A

acts locally
affects cell nearby
short lived signal
(neurotransmitters)

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9
Q

What is autocrine signaling?

A

cells resign to signals they themselves relates or release to cells of the same type
cells secrete signal that feeds back and binds to a receptor on its own surface

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10
Q

What is direct cell signaling?

A

ex) immune cells

Ag-presenting cells to T cells

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11
Q

What do cells do after receiving a signal?

A

survive
divide
differentiate
die

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12
Q

What are the three parts of a signaling module?

A

signals
receptors
effectors

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13
Q

What are signals?

A

(ligands)
Typically secreted by exocytosis
signals stay near or far

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14
Q

what are receptors?

A

bind specifically to signal molecules with high affinity (signals are produced in low levels)

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15
Q

What are effectors?

A

targets of receptors inside cells: alter activity of many different proteins and generate 2nd messengers (small diffusible molecules like cAMP and Ca2+)

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16
Q

What are the main categories of ligands?

A

small lipophilic molecules: steroid hormones

water soluble molecules - hydrophilic- e.g. growth factors

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17
Q

Receptors can bind to ligands with _____ affinity, which means ____

A

high; great specificity to the ligand (conc of ligand is low in bloodstream)

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18
Q

What are the two types of receptors?

A

cell surface receptors

intracellular receptors

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19
Q

What are cell surface receptors?

A

external domain binds ligand, transmembrane domain anchors receptor, cytoplasmic domain initiates signal by change in conformation

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20
Q

What are intracellular receptors?

A

steroid receptor can have receptor in cytosol- alters gene expression in nucleus

21
Q

Most signaling molecules are hydrophilic and require ______

A

cell surface receptors

22
Q

One major class of surface receptors that mediate transduce a binding event on the cell surface to send signal inside the cell

A

G protein coupled receptors

23
Q

What is a G protein coupled receptors?

A

receptor composed of 3 parts:
extracellular domain
transmembrane domain
cytoplasmic domain

24
Q

What does the extracellular domain do?

A

binds to ligand

25
Q

What does the transmembrane domain do?

A

anchors receptor

26
Q

What does the cytoplasmic domain do?

A

associates with G protein

27
Q

What are the three protein subunits of G proteins

A

alpha, beta, gamma

28
Q

What are the 3 components of G protein coupled receptor pathways?

A

inactive receptor
receptor G protein
inactive effector

29
Q

G protein coupled receptors are characterized by _______

A

seven membrane spanning alpha helices

30
Q

What type of proteins are G proteins? what do they assist in?

A

guanine nucleotide binding proteins

assit in transmitting signals to intracellular targets

31
Q

What is an example of an effector?

A

downstream adenylyl cyclase that generate cAMP

32
Q

What are the steps of G-protein relaying signals?

A
  1. ligand binds to receptor
  2. conformational change occurs in receptor
  3. receptor binds to G protein
  4. receptors acts as guanidine exchange factor
  5. confirmation of G alpha protein is changed to kick out GDP for GTP
  6. G alpha becomes active and binds effector molecule to activate it
  7. effector molecule can catalyze formation of cAMP
33
Q

What is the target in the cholera toxin?

A

G protein

34
Q

What does cholera do to G protein?

A

modifies it by keeping the G alpha in the GTP active form indefinitely, pathway is always active causing Cl- and water to pump out of cells in intestines to cause severe diarrhea

35
Q

G alpha s stimulates ________

A

adenyly cyclase

36
Q

G alpha I inhibits _______

A

adenyly cyclase

37
Q

cAMP interacts with target proteins to cause a _______ and activates a protein kinase called ______

A

biological response; PKA

38
Q

What does a kinase do?

A

phosphorylates proteins to either activate or inactivate them

39
Q

________ induces activation of PKA

A

epinephrine

40
Q

What does the downstream do?

A

generate lots of ATP for a response to threat
in liver: glycogen breakdown to glucose, inhibition of glycogen synthesis
cardiac muscles: increase contraction rate
adipose tissue: hydrolysis of triglycerides to generate more glucose

41
Q

What is desensitization?

A

ability to turn off or reject the signal

42
Q

What ways can desensitization occur?

A

receptor sequestration
receptor destruction
hormone level drop
remove the signaling molecule

43
Q

What is receptor sequestration?

A

endoscope- invagination of membrane

44
Q

What is receptor destruction?

A

endoscopes and lysosomes

45
Q

What is hormone level drop?

A

decreased adenyly cyclase activity to decreased cAMP and decreased PKA activity

46
Q

What is removing the signal molecule?

A

phosphodiesterase will remove cAMP

47
Q

What do G protein receptor kinases do?

A

phosphorylate the receptor such that another protein called arresting will bind to the 3rd intracellular loop of receptor and prevent G alpha from interacting with third loop of the receptor

48
Q

What does GRK result in?

A

G protein G alpha-GDP does not get converted to G alpha-GTP by receptor

Molecular Exam 2 (13 decks)

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