Chapter 9 Flashcards
Ligand
Specific molecule that binds with receptor
Receptor
membrane proteins, ligand binds to it
Signal propogation
ligand ->
receptor ->
intracellular signal transduction ->
response
Earl Sutherland Experiment
Vanderbilt 1951, studying epinephrine (adrenaline) stimulates glycogen breakdown, free up sugars in blood and meet immediate energy needs, fight or flight response
Nobel Prize 1971
Epinephrine insights
linked to glucose production
glycogen phosphorylase activity increased
no direct connection
cells must be intact/functional
Forms of cell signaling
Intra vs intercellular
autocrine
gap junctions
paracrine
endocrine
Gap Junction and direct signaling
Cell to cell connection
gap junctions
plasmodesmata (in plants)
fluid filled
small signal molecules
Channels with high specificity
cells are independent
respond quickly
coordinate response of cells
all plant cells are connected (plasmodesmata)
Autocrine
Targets and effects self
signal = target cell
early development
ex: macrophage makes itself inflamed because of detected virus
Endocrine
Distance signaling
slower response
longer lasting
endocrine glands (thyroid; adrenal)
ligand = hormones
travels in bloodstream
Paracrine
Immediate/fast communication
short-lived response
ex chemical synapses
neurotransmitters
Internal receptors
inside of the cell
cytoplasmic/intracellular
interact with hydrophobic ligands
pass through PM -> cytoplasm
bind w ligand -> nucleus
regulate gene expression
Cell surface receptors
Outside of the cell
transmembrane receptors
anchored to plasma membrane
ligands interact/stay outside
signal transduction
external signal -> internal signal
Ion channel linked receptors
ligand binds to channel, opens channel, specific ions pass through
G protein receptors
specialized “G protein”, with channel or enzyme, important immune function
Enzyme linked receptors
catalyze rxn. in PM
extra and intracellular domain
ex: HER2 receptor/breast cancer
Small hydrophobic ligands
non-polar; diffuse directly across PM
interact with internal receptors
steroid hormones
thyroid hormone and vitamin D
carrier proteins deliver them ( cant dissolve in blood)
Water soluble ligands
polar; will not readily diffuse
bind to extracellular domain
cell-surface receptors
diverse; peptides and proteins
Nitrous Oxide
Gaseous; short-lived
interacts with smooth muscle
induce relaxation of tissue
Nitroglycerin helps release
Stages of cell communication
signal reception -> membrane protein receives signal
signal transduction -> single/multistep signaling pathway
cellular response -> elicits specific cellular response
Signaling pathways
binding of ligand (activates protein); signal initiation, pathway, integration
intracellular signaling (phosphorylation)
second messenger after ligand binds spreads signal through cytoplasm
cell response to signals
regulate gene expression
increase cell metabolism
Cell growth and division
programmed cell death
signal termination
Phosphatases
enzyme that stops signal
Signaling in unicellular organisms
signaling occurs via specific molecules
detected by other bacteria
quorum sensing
monitor local density, coordinate behavior, biofilms
Signaling Cascade
Series of chemical reactions that occur in a cell
Secondary Messengers
Propagate signal through cytoplasm
Caspases
enzymes involved in apoptosis
Quorum sensing
Cell to cell communication process, allows bacteria to sense environment
