Communication Flashcards
Bacteria communicate with one another using
chemical signal molecules
Bacteria examples of cell communication
Myxococcus xanthus fruiting body formation
Escherichia coli flagellar rotation
Biofilm formation
Sporulation in Bacillus
Mating yeast cells
Use chemical signaling to identify cells of opposite mating type
How many mating yeast types
Two mating types in sexual reproduction
a and a- are haploid
Process of mating yeast cells
Exchange mating factors
Release specific mating factors
Only bind to receptors on other cell type
Change shape and grow toward each other
End product of mating haploid yeast cells
New a/a cell (diploid)
Contains ALL genes of both original cells
3 steps of the mating yeast cells
exchange mating factors
mating
new diploid cell a/a- cell
what types of signaling are there
contact
local
long distance
Communication requiring contact between cells
Cell junctions (gap junctions; plasmodesmata) Cell-surface molecules
Local signaling (few cells distance between)
Paracrine signaling
Synaptic signaling
Local paracrine signaling
Secretion of local regulator (i.e., growth factor)
Local synaptic signaling
Release neurotransmitter into synapse, stimulating target cell
Long-distance signaling (up to body-length distance)
Endocrine (hormonal) signaling Plant hormone (1 example)
long distance endocrine signaling
Specialized endocrine cells secrete hormones into body fluids
(examples: insulin, epinepherine)
Hormones reach most body cells, but bind and affect only some cells
long distance Plant hormone (1 example)
Ethylene (C2H4) promotes fruit ripening and regulates growth
3 stages of cell signaling
Signal Reception
Signal Transduction
Cellular Response
Cell division
1st stage of cell signaling– signal reception
-Signaling molecule (ligand) binds to receptor protein
Peptides, proteins, amino acids, lipids, gases, etc.
-Receptor protein changes shape
2nd stage of cell signaling–Signal Transduction
- Relay signals from receptor(s) to target molecule(s)
- Protein phosphorylation and dephosphorylation
- Signal transduction pathway
3 rd stage of cell signaling Cellular Response
- Cell division
- Regulation of transcription
- Enzyme activation and inactivation
what happens in signal reception
Signaling molecule binds to a receptor, causing conformational change in receptor
what are receptors for signal reception and where are most
G protein-coupled receptors (GPCRs)
Receptor tyrosine kinases
Ion channel receptors
in plasma membrane
Intracellular receptors for reception
In cytoplasm, nucleus, organelle
G protein-coupled receptors (GPCR)
Receptor works with G protein
Large family of eukaryotic receptor proteins
Single polypeptide has 7 transmembrane (TM) a helices
GPCR binds with
Binds GTP (guanosine triphosphate)
G-protein coupled receptors Diverse functions roles in:
Embryonic development
Sensory reception
Human vision, smell, taste
Malfunctions of GPCRs lead to
many human diseases, including bacterial infections
Cholera, pertussis (whooping cough), and botulism
due to bacterial toxins that interfere with G protein function
4 steps in g protein receptor
look at pp slide 8
-GDP bound to G protein = inactive
-Activated receptor (signal molecule binds) causes GTP to displace GDP
-Activated G protein diffuses along membrane, binds to an enzyme, activating it
-G protein acts as GTPase
GTP + H2O → GDP + Pi
Shuts down pathway
What happens if GDP is bound to g protein
in active
What happens when G protein receptor is activated
GTP to displace GDP
GTP bound to GTP is active now
What happens to the activated g protein
diffuses along membrane
binds to enzyme
activates enzyme
When the G protein acts as GTPase what happens
shuts down pathway
