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Cell Communication

Chapter 11

Jaclyn Severn

on 21 November 2016

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Transcript of Cell Communication

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
Yeast Mating
Yeast shmoo mutants & the shmoo formation pathway
Graphic Yeast Sex
Quorum Sensing
Fruiting Body Formation in Soil Bacteria in response to poor environmental conditions
Plaque Biofilm All Up On Your Teeth!
communication among microbes that triggers group response once particular population densities are reached
Vibrio fischeri
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.
Model of quorum sensing in V. fischeri.
Don't worry about the specifics, focus on the big picture
Low density
High density
Biofilms are bacterial ecosystems that are established and maintained due to elaborate quorum sensing networks
It's All About Signal Reception!
Cellular Communication
Big Questions
Why do cells communicate?

What does cellular communication look like?

How is cellular communication utilized in unicellular and multicellular life?
Make Sure You Can
How Cells Communicate: Signal Transduction
The 3 Phases of Signal Reception
Local Signals
How Signals are Recieved
The ligand isn't important.
The Response is!
Cells Amplify A Message
Things Get Complicated Quickly
Different Chemistry
Different Reception
Different Responses
An Epinephrine Receptor
What kind of hormone is epinephrine (polar or non-polar)?
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?)
Internal signaling molecules released due to external ("first") signals. Trigger sub-response pathways.
Programmed cell death is programed because of the signalling pathway that it is programmed to.
Epinephrine is a polar amine ligand
Why Cells Communicate: Some Examples
How Signals Are Sent
Long Distance Signals
The Nervous and endocrine systems handle these things in animals. We will talk about them in depth, later in the course
Signaling Pathways
Second Messengers
Widely conserved among all domains (why?)
G-Protein Linked Reception
Tyrosine Kinases
Ligand-gated Ion Channels
proteins activated by the transfer of a phosphate from a molecule of GTP.

The first step in the protein relay
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.
The incoming ions trigger the response
Cyclic AMP: A typical second messenger that affects metabolism.
Calcium ions are another common second messenger.
An Example
Aka "Adrenaline"
A common hormone in vertebrates.
Involved in short term stress ("fight or flight") response.
More from less
What kind of feedback?
A "Branching Network"
Simplicity leads to Complexity
Other Signals
Pretty much any chemical or energy source could serve as a biological signal...

...though most are biologically created molecules
Note: We will only look at unicellular examples in this lesson (animals and plants later!)
How can this kind of behavior evolve?
Notice that death proteins are present in an inactive form prior to signal reception (Why?)
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 patways to actual examples as discussed in this presentation.

Discuss the evolutionary/adaptive considerations of cellular signaling pathways.
Here's an example:
Full transcript