Chapter 15 Flashcards
Cell signaling
What are the five forms of signalling?
Endocrine
Paracrine
Autocrine
Synaptic
Contacts-dependent
What is endocrine signalling?
Long distance signaling by molecules secreted to the blood
What is paracrine signalling?
Local signaling to neighboring cells
What is autocrine signalling?
Signaling to the cell itself
What is synaptic signalling?
Signaling along nerves, involving an electrical pulse and neurotransmitters
What is contacts-dependent signalling?
Interaction between molecules on the surface of cells
What is the function of a coincidence detector?
A coincidence detector requires activation from two separate signaling events. This way the chance of coincidental activation is diminished.
It functions to incorporate two spatially separated signals into one signal
Define downstream and upstream
RNA
Downstream - towards 5’ end
Upstream - towards 3’ end
DNA
Downstream - towards the 3’ end of the coding strand
Upstream - towards the 5’ end of the coding strand
What is receptor desensitization/adaption?
Alteration of sensitivity following repeated stimulation, reducing a cell’s response to that level of stimulus
What is receptor down-regulation and up-regulation?
A cell decreases or increases the quantity of a cellular component, such as RNA or protein, in response to an external stimulus
What is a receptor?
General term for a protein that binds a specific extracellular molecule (ligand) and initiates a response in the cell
What is receptor sequestration?
Change in the receptor conformation such that binding of the agonist does not activate the receptor
What is positive feedback?
The enhancing or amplification of an effect by its own influence on the process which gives rise to it
Generally promotes instability
Explain the mechanism of G-protein-coupled receptor (GPCR) activation?
When an external signaling molecule bind to a GPCR it causes a conformational change
The change triggers the interaction between the GPCR and a nearby G-protein
Alpha subunit dissociates from the receptor and the beta-gamma subunt
GTP is exchanged for GDP, which activated the alpha subunit
The G-protein alpha subunit then goes on to activate other molecules in the cell
Explain the mechanism of G-protein-coupled receptor (GPCR) activation?
When an external signaling molecule bind to a GPCR it causes a conformational change
The change triggers the interaction between the GPCR and a nearby G-protein
Alpha subunit dissociates from the receptor and the beta-gamma subunt
GTP is exchanged for GDP, which activated the alpha subunit
The G-protein alpha subunit and beta-gamme subunit can then relay messages and interact with other membrane proteins.
What is a G-protein?
Specialized proteins with the ability to bind the nucleotides guanosine triphosphate (GTP) and guanosine diphosphate (GDP)
G-proteins that associate with GPCRs are heterotrimeric - have three different subunits.
Active - bound GTP
Inactive - bound GDP
Identify cAMP
(Ring structure around phosphor atom)
What is Guanine nucleotide exchange factor (GEF)?
a) Protein that binds to a GTP-binding protein and activates it by stimulating release of tightly bound GDP, thereby allowing it to bind GTP
What is an interaction domain?
Compact protein module that binds to a particular structural motif in another protein (or lipid) molecule with which the signaling protein interacts
What is a kinase cascade?
A signal relay chain involving multiple protein kinases, each of which is activated by phosphorylation and then phosphorylates the next protein kinase in the sequence
What is a second messenger?
Small molecule that is formed in the cytosol, or released into it, in response to an extracellular signal and that helps to relay the signal to the interior of the cell
What defines an endrocrine cell?
Specialized animal cell that secretes a hormone into the blood
What is a protein kinase?
Enzyme that transfers the terminal phosphate group of ATP to a specific amino acid of a target protein
What is a neurotransmitter?
Small signal molecule secreted by the presynaptic nerve cell at a chemical synapse to relay the signal to the postsynaptic cell