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C Bio > Cell Signalling 1 (19) > Flashcards

Cell Signalling 1 (19) Flashcards

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Biology 101 flashcards
1
Q

what type of organisms are entirely reliable on signals from their envr?

A

single celled organisms

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2
Q

multi cell organisms receive signals form other cells that signal for what?

A

cell division

differentiation

death

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3
Q

Autocrine signaling

A

bind to receptors on cells that secrete them

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4
Q

what type of signaling do T-cell lymphocytes practice? & what molecule is excreted?

A

autocrine signaling

interleukin-2, cytokine

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5
Q

paracrine signaling

A

bind receptors & stimulate nearby cells

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6
Q

endocrine signaling

A

occurs when cells secrete signaling molecules into the blood
long distance, goes throughout the body

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7
Q

what type of signaling molecules are hormones?

A

endocrine signaling

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8
Q

synaptic signaling

A

similar to paracrine signaling but the signal is passed through a synapse (space) b/w the transmitting cell & the receiving cell; occurs b/w a neuron & another cell (usually another neuron or muscle cell)

specialized paracrine signaling

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9
Q

signaling by cell contact

A

must have cells with adjacent PMs (direct conduction from one cell to another without passing through the ECF)

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10
Q

gap junctions are what kind of signaling?

A

signaling by cell contact

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11
Q

whats the difference b/w lipophilic & lipophobic signals?

A

Lipophilic –> cross the PM, receptors are intracellular
Steroid hormones

Lipophobic –> don’t cross PM, receptors are extracellular
Any PRO based signal
Signals are transduced & amplified

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12
Q

transduction

A

process by which a signal crosses the membrane or is transferred to other molecules

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13
Q

amplification

A

process by which the effect of a signal is multiplied/increased

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14
Q

what are 2 ways transduction occurs?

A

phosphorylation

GPROs

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15
Q

phosphorylation transduction & ex

A

ligand binds to receptor, PRO gets phosphorylated & receptor may be mediating it & triggering events inside the cell

RTK receptors

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16
Q

G PRO transduction

A

extracellular receptor binds ligand, once bound will trigger a G PRO & that will amplify a signal causing cell to respond accordingly

17
Q

summary of transduction & amplification

A

receptor binds signaling molecule

receptor changes shape

Shape change enables the receptor to interact with intracellular PROs

2nd messenger molecules are produced to amplify the signal

various effects can occur from 1 ligand

18
Q

what are 2nd messengers responsible for?

A

transduction

19
Q

what are 3 reasons why amplification is important?

A

Initial signaling molecule (hormone) to be in limited concentrations & still be effective

One hormone to activate numerous enzymes (one kinase molecule can activate many other kinase molecules)
(so it has a large enough effect to cause an event)

Coordination of several pathways simultaneously as all are induced by a single signal

20
Q

summary of steroid hormones producing an endocrine signal

A

steroids are made from cholesterol (small & fat soluble)

travel through blood via carrier PROs

enter cells via diffusion

steroid has a high affinity for receptors in the cytoplasm or nucleus

hormone receptor complex binds to DNA at the promoter region, upstream of genes

transcriptional enhancement occurs

(slow, long-term response)

21
Q

what are some types of steroid hormones?

A

glucocorticoids (including cortisol)

estradiol

testosterone

progesterone

22
Q

what are the steps in activating glucogenesis?

A
  1. Diffuses into cell
  2. Binds specific receptor (PRO)
  3. Receptor dimerizes
  4. Dimer enter nucleus
  5. Dimer binds to GRE response element (DNA) on the PEPCK promoter (& other genes)
  6. Increases transcription rate, enzyme amount & enzyme activity gluconeogenesis
23
Q

what are the kinds of lipophobic hormones?

A

water soluble hormones

PROs

neurotransmitters

cell-cell contacts

24
Q

when is signal transduction used?

A

lipophobic signaling molecules

25
Q

what are the steps in the signaling pathway for lipophobic signals?

A
  1. Recognition of stimulus by cell-surface receptor (specific, sensitive)
  2. “Transfer” across the membrane doesn’t ship ligand, receptor changes shape b/c of ligand & can now interact with an effector
  3. Effector (ex: adenylyl cyclase) molecules or a series of molecules on the interior of the membrane or cytosol create the next message (cAMP or calcium ions); usually a series of intervening steps before ultimate response (activations/inactivations)
    Can produce 2nd messengers
  4. Cessation of the response when signal disappears (ex: cAMP phosphodiesterase)
26
Q

what are the diff kinds of movements in the nematode?

A

normal = sinusoldial

mutant G PRO - hyperactivity, sidewinding & twisting

mutant G PRO - lethargy, slow & limited tracks

27
Q

what is the structure of a G PRO coupled receptor?

A

7 transmembrane domains

alpha helices

28
Q

how do G PRO coupled receptors work?

A

through heterotrimeric G PROs

Alpha, beta & gamma subunits
Alpha & gamma both are embedded in the membrane
Beta subunit is free to move elsewhere

Turn on effector molecule which makes the 2nd messenger
Ex: epinephrine & glucagon turn on adenylyl cyclase to make cAMP (2nd messenger)
Others (ex: acetylcholine) use phosphoinositol, DAG 2nd messengers
Others (ex: photoreceptors) use cyclic GMP

29
Q

how are GPCRs involved in making 2nd messengers?

A

binding the ligand causing a conformational change allowing the G-PRO to interact with the effector that produces the 2nd messenger signal

30
Q

GPCR steps

A
  1. Ligand binds to receptor, shape changes & alpha subunits binds to receptor PRO
  2. Activation of the G PRO: exchanges GDP for GTP (no hydrolysis)
  3. RELAY: alpha dissociates from beta & gamma & binds to effector
  4. Activated effector produces 2nd messenger
  5. Alpha subunit hydrolyzes GTP –> GDP & deactivates itself
  6. Alpha subunit with GDP binds with beta & gamma subunits (trimeric PRO)
  7. G PRO coupled receptor kinase (GRK/GPCRK) phosphorylates the receptor
  8. Arrestin binds to phosphorylated receptor preventing it from binding with G PROs
31
Q

how do G PROs differ from one another?

A

alpha subunits

32
Q

what subunit besides the alpha subunit can activate effectors?

A

beta-gamma complex

33
Q

steps of the cholera toxin causing water loss

A

Toxin binds to the receptor

Toxin brought into the cell via endocytosis

Cholera toxin binds to the alpha subunit

alpha subunit binds to adenyl cyclase with the toxin & is active

adenyl cyclase produces cAMP

cAMP activates the chloride channel

Na+ & water follow chloride ions out of the cell

34
Q

Steps in stopping the GPCR signal

A

G RPO hydrolyzes GTP, inactivating itself

Receptor is phosphorylated

Phosphorylated receptor binds arrestin

Arrestin binds to clathrin

Endocytosis of receptors occurs

C Bio (30 decks)

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