cell phys exam 4

what are the major questions in cell signaling

• what types of signals do cells receive

• how do cells recognize signals

• how do cells respond to cell signals

• how do cell signals affect cell function

what is the major concept in cell signaling

all living things process information from the environment

• the information exists as signals that cause and effect

what are the four types of intercellular signaling

• contact-dependent

• paracrine

• synaptic

• endocrine

what is an example of contact-dependent intercellular signaling

membrane-bound signal molecule, cadherin

what is an example of paracrine intercellular signaling

local mediator

what is an example of synaptic intercellular signalling

nuerotransmitters

what is an example of endocrine intercellular signaling

hormones

what kind of signaling happens fast

ion channels, kinase

what kind of signaling happens slow

gene expression changes

what does signaling speed depend on

speed will depend largely depend on how stable the signaling components are

describe positive feedback

the output stimulates its own production of

describe negative feedback

the output inhibits its own production

what is the cell signaling nomenclature for activation

A ——> B

What is the cell nomenclature for inhibition

X ——> Y

What are the three types of cell surface receptors

• ion channels

• g-protein receptors

  • enzyme-coupled receptors

describe ion channels

• mediate rapid signaling between nerve cells

• neurotransmitters open and close channels

• result in changes in target cell excitability

describe g-protein receptors

• uses trimeric GTP-binding protein (g-protein)

• g-protein binds to target proteins that change ion permeability or intracellular signaling

describe enzyme-coupled receptors

• usually single-pass TM receptors

• ligand binding site facing the outside and a catalytic/enzyme site on the inside

• usually are kinases or coupled to kinases

what can intracellular signals be

• second messengers

  • chemicals such as calcium, cyclic amp, diacylglycerol

• proteins

  • generate more second messenger or activate/deactivate another protein

what are the three types of cell signaling components

• g-protein coupled receptor

• secondary messengers

• receptor tyrosine kinases

what happens when a ligand binds to a GPCR

the GPCR is activated

what happens once the GPCR is activated

once activated, GPCRs transmit the message to trimeric g-proteins that relay the signal to other targets

describe the structure of the g-protein

the g-protein is made of 3 subunits: alpha, beta, and gamma

describe the alpha subunit

the alpha subunit is bound by GDP when g-protein is inactivated

GPCR Signaling Overview

• the GPCR binds a signal

• binding of the signal causes a conformational change in the receptor allowing it to interact with the trimeric g-protein

• the g-protein also changes confirmation leading to release of GDP from the alpha subunit

• alpha subunit then binds GTP (receptor acts as the GEF) causing activation and dissociation of beta/gamma complex

• GTP is eventually hydrolyzed to GDP causing inactivation through association with RGS, a type of GAP (GTPase Activating Protein)

which amino acid residues get phosphorylated

• Serine, threonine, tyrosine

  • they all have nucleophilic (-OH) group

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