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Simplicity leads to Complexity
Why do cells communicate?
What does cellular communication look like?
How is cellular communication utilized in unicellular and multicellular life?
Explain why and how cells communicate with the environment.
Explain the common features shared among cellular communication processes.
Compare the purpose of cellular communication in unicellular and multicellular organisms
Describe the major features of signal transduction pathways in cells.
Connect cellular signaling pathways to actual examples as discussed in this presentation.
Discuss the evolutionary/adaptive considerations of cellular signaling pathways.
Why Cells Communicate: Some Examples
How Cells Communicate: Signal Transduction
An Example
An Epinephrine Receptor
Widely conserved among all domains (why?)
G-proteins:
proteins activated by the transfer of a phosphate from a molecule of GTP.
The first step in the protein relay
What kind of hormone is epinephrine (polar or non-polar)?
communication among microbes that triggers group response once particular population densities are reached
Epinephrine is a polar amine ligand
Programmed cell death is programed because of the signaling pathway that it is programmed to.
Vibrio fischeri
Epinephrine signal transduction is mediated by G-Protein linked receptors.
It has multiple effects, but one response is the inhibition of glycogen synthesis and the acceleration of glycogen breakdown (why?)
A bacterium that lives inside organs in marine animals.
When population density hits a threshold, they begin to produce a light-producing protein.
This gives the host animal bioluminescence.
Mating type in (haploid) yeast is genetically determined.
Two mating types (a and alpha). Each makes signaling molecules that the other receives.
The reception of a mating factor leads to the production of a mating "Shmoo"
Fusion of shmoo's = diploid yeast cell.
Meiosis soon ensues
Kinase: A protein that "phosphorylates" (adds a phosphate) to another molecule
Tyrosine Kinases:
proteins that form dimers. Tyrosine amino acid residues are active in the transfer of phosphates to relay proteins.
Remain active as long as the ligand is attached.
More from less
Cells Amplify A Message
Biofilms are bacterial ecosystems that are established and maintained due to elaborate quorum sensing networks
The incoming ions trigger the response
The Nervous and endocrine systems handle these things in animals. We will talk about them in depth, later in the course
Notice that death proteins are present in an inactive form prior to signal reception (Why?)
Yeast shmoo mutants & the shmoo formation pathway
Plaque Biofilm All Up On Your Teeth!
Fruiting Body Formation in Soil Bacteria in response to poor environmental conditions
Pretty much any chemical or energy source could serve as a biological signal...
...though most are biologically created molecules
Internal signaling molecules released due to external ("first") signals. Trigger sub-response pathways.
A "Branching Network"
Things Get Complicated Quickly
How can this kind of behavior evolve?
Things