Cell Communication Ap Bio Essay

Transcript of AP Bio- Communication 1: Cellular 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 signaling 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
: 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 pathways to actual examples as discussed in this presentation.

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

Full transcript

AP Biology 3/20/11 Cell-to-Cell Comm. Describe the communication that occurs and the types of responses that result from this communication. A. Communication between two plant cells While on an organismal level, plants respond to stimuli by quite different means than animals do, on the cellular level they use similar, often homologous processes that can be just as complex as those of animals. Plants have their own type of hormones, also called plant growth regulators, which are transported throughout the organism and function to activate signal transduction pathways in the same way an animal hormone would. These hormones enable plant cells to communicate with one another and respond to stimuli. They are interpreted via the same “reception, transduction, response” sequence as animal hormones. Once a plant cell secretes a hormone, it travels through the organism (or, in some local signaling cases, crosses directly to the receiving cell) and reaches a receptor, either on the surface or in the cytoplasm or nucleus of another plant cell. The receptor, often of the tyrosine kinase type, is specific to each individual stimulus, and can commence transduction either directly or through the use of a second messenger. The transduction pathways in turn result in an alteration of the cell’s DNA transcription process, resulting in a cellular response. There are many different types of plant cell hormones, all of which result in different types of cellular responses. Their balance controls nearly every aspect of organismal growth and development by affecting the “division, elongation, and differentiation of cells.” Plant hormone types include auxin, cytokinins, giberellins, brassinosteroids, abscitic acid, and ethylene. Auxin functions by moving quickly from the basal end of one plant cell to the apical end of a neighboring cell. As a result, it can stimulate cell elongation, in addition to lateral root formation. Cytokinins move from cell to cell in a similar fashion to auxin, but instead affect cell division and differentiation, cellular aging processes, and apical dominance. Giberellins function slightly differently; plant cells secrete them and they subsequently travel through the extracellular fluid until they reach their designated receptor. They affect stem elongation, seed termination, and fruit growth. Brassinosteroids, a type of steroid, induce cell elongation and stem segment

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