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Intro
exam 2 - signaling
15
Medical
Professional
09/14/2011

Additional Medical Flashcards

 


 

Cards

Term
examples of adaption to avoid desensitization
Definition

alternating drug delivery to every other day

 

pulsatile release of hormones like how the hypothalmus does - it releases hormones in pulses very 20 mins

 

these are self regulatory processes

Term
why would a cell have spare receptors
Definition

to allow for an alternate signal transduction.  one signal will be carried out at low agonist conc and a diff will be carried out at high.  like insulin: low conc stim glucose uptake, high works as a growth factor

 

also, it can make a target cell more sensitive to the hormone

Term
what kind of agonists act on PM surface receptors?
Definition

water soluble agonists and proteins

 

small lipid solubles like prostalandins

Term

what kind of agonists act on cytosol and nuclear receptors?

Definition
lipid soluble molecules, steroids, thyroxin, retinoids
Term
what are the differences in receptor affinities for agonists for hormone receptors and neurotrasmitter receptors?
Definition

hormone receptors usually have a very high affinity for their agonists that that they can take place in long activations of their pathways.

 

neurotransmitters require more agonist and therefore have a lower affinity.  this is necessary to maintain quick on/off activiation capabilities

Term

what happens when you lower receptor saturation?

 

raise saturation?

Definition

the receptors become more sensitive to any agonist present and the result is upregulation of activity.  this is also true if there is competitive inhibition since the true saturation of meaningful agonist is low

 

raise the saturation and tolerance begins to occur. down-regulation of activity takes place

Term
what pathology can happen to the nicotinic ach receptor?
Definition
curare, a snake toxin and bind to it and block acetylecholine binding.  this wont allow the ion channel to open and since it is is a postganglion neuron at the neuromuscular junctions, paralysis can insue
Term
describe a cAMP-using pathway
Definition

GTP bound alpha sub activates adenyl cyclase, AC converts ATP to cAMP, cAMP activates PKA, which can phosphorylate or activate any number of kinases

 

i.e. CREB -> CREB-P which when activated can go to the nucleus and stimulate transcription

Term
what can cholera toxin do
Definition
cause ADP ribosylation which abolishes GTPase activity leaving the G-protein constitutively on
Term
common large g-protein second messengers
Definition

cyclic nucleotides, cAMP, cGMP

intracellular Ca2+

membrane phospholipid breaddown products like IP3 and DAG, arachidonic acid, and aicosanoids

Term
calcium as a second messenger
Definition

cannot be created or destroyed, just moved around.

 

at a higher conc outside the cell

 

it can work with calmodulin (a Ca binding protein like toponin C).  calmodulin may be present on the surface of an enzyme and Ca binding to it may activate, or it may be free floating and when they bind together they make a complete agonist.  Calmoudin has 4 binding sites

Term
creation of IP3 and DAG
Definition

a phospholipase (such as phospholipase C) that has been activated by the alpha subunit of a large G protein can cleave PIP2 which is connected to the PM.  DAG will stay membrane bound.  DAG is then capable of activating PKC, which phosphorylates and alters many others

 

meanwhile, IP3 binds to receptors on ER and releases CA2+ stores.  Ca2+ can increase the activity of PKC.

Term
uses of arachadonic acid as a second messenger
Definition

a phospholipid tail which can be cleaved by phospholipase A2.  it can now serve as a signalling molecule, or a parent molecule for other future messengers, or diffuse out of the cell and have profound paracrine effects on neighboring cells

 

it can also be metabolized into compounds called eicosanoids. 

Term
what is something that the beta-gamma G-protein subunits can activate?
Definition

K+ ion channels in the heart.

 

and Ach receptor in the vagus nerve

Term
what does aspirin inhibit?
Definition
both isoforms of COX (1 and 2)
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