exam 3- lecture 11 Flashcards
what do all cells do from the environment
process information
what does a signal transduction pathway do
sequence of molecular events and chemical reactions that lead to a cells response to a signal
steps in cellular signalling
- the signal binds to a receptor, activates
- the signal is transmitted to the interior of the cell by a signal transduction pathway
- the cell responds by activating an enzyme or turning on the transcription of a gene
- the response is terminated so that new signals can be received
at low cell density
the concentration of the signaling peptide is too low to stimulate DNA uptake by bacteria
at high cell density
the concentration of the signaling peptide is high enough to stimulate the DNA- uptake response
types of cell signaling
- endocrine
- paracrine
- autocrine
- contact-dependant
endocrine signals do
travel to distant cells, by the circulatory system
paracrine signals affect
nearby cells, in the nervous system
autocrine signals affect
the cells made by them
contact dependant signals have
no diffusion and cells touch
what are the two types of cell signaling receptors
membrane
intracellular
membrane receptors are
in the plasma membrane and bind polar lignads
ex insulin (protein)
intracellular, or cytoplasmic, receptors are
in the cytoplasm and bind nonpolar ligands that can diffuse across the pm
ex estrogen, a steroid lipid
binding the ligand causes the receptor protein to
change chape or conform
what can also bind to receptor proteins
inhibitors or antagonists
how do signal receptors initiate a cellular response
G protein-coupled receptors
Heterotrimeric G proteins
G protein-coupled receptors
bind heterotrimeric G proteins
ligand binding to GPCRs activates G proteins
Heterotrimeric G proteins
Membrane-associated proteins with three subunits
Bind GDP (inactive) or GTP (active)
GTP bound alpha subunit separates from the other subunits and encounters an
effector protein
what does the enzyme adenylyl cyclase do
catalyzes the formation of cAMP from ATP
how is the response to a signal transduced through the cell
first messenger
second messenger
how does the first messenger go through the cell
ligand signal
how does the second messenger go through the cell
small water soluble, non-protein molecule
relays the initial signal to target molecules inside the cell
amplify the signal
1 molecule of adrenaline makes
1000s of glucose molecules
