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LIFE! (A BRIEF snapshot)
HTTP://WWW.PBS.ORG/WGBH/NOVA/EVOLUTION/ORIGINS-LIFE.HTML
Atmospheric Stuff of Life-
Coacervates
When exactly (what criteria) do we
obtain a living cell?
Cellular
Reproduction
Growth/Development
Metabolize
Respond
Evolve
Prokaryotes-life’s first fully
independent creatures
See hand out, or better yet, the colored version on the ppt!
So, what are some basic
environmental conditions cells had
to evolve to overcome? (In order
to exsist and thrive?)
So what drove complexity?
In no small part, the cyanobacteria
Evolutionary flow chart for cellular
achievement Coacervate (empty cell) formation-anaerobic
prokaryotes- aerobic prokaryotes aerobic
eukaryotes & anaerobic eukaryotes (individual cells)
multicellular aerobic and anaerobic organisms
First mass extinction-End of the
archaea-bacteria reign!
Darn the cyanobacteria!
Favored heterotrophic chemosynthetic bacterium
Increase complexity of DNA
Who is LUCA? (Traits)
Who is still around?
Who is more ancestral?
Revisit diagram (hand out)
So the environment is the spark to
cellular evolution.
Today’s relationship?
Endosymbiosis http://highered.mheducation.com/sites/9834092339/student_view0/
chapter4/animation_-_endosymbiosis.html
Cell size and function!
Why do cells remain small?
SA:V ratio
How do we compensate for small size?
Why does evo favor all this
additional boundary complexity?
HOMEOSTASIS (Mr Prey!)
The Leftovers?
Viruses
Prion
Back to the idea of maintenance
of cellular life? How do we
maintain internal homeostasis?
Cellular structures
Chemical properties- Water potential
Enzyme reactions
Chemical reactions/Chemical presence (+/-)
What do ALL (cells) continue to
share? (Structurally)
Although ONLY eukaryotes have all the extras!
Must knows: phospholipid by-layer (orientation), 5 types of glycoproteins
(see next slide), cholesterol, carbohydrate chains/antenna
Critical components (extras) in
eukaryote membrane evolution
Phosphate (polar)-lipid (non-polar)molecule
(phospholipids)-all about passive movement
5 types of large glycol-proteins : Adhesion,
Communication, Identification, Transport, Receptor
Sugar molecule (carbohydrate) antenna
Sterols-support
Why need all these extras??
Outside the cell membrane-cell
walls
Peptidoglycan (Prokaryotes only…huge in medicine!)
Chitin-fungi
Cellulose-plants
NONE-animals
4 ways to communicate
Carbohydrate antenna
Ion concentration and exchange
Chemical close or far
Tactile
3 areas for communication
For chemical communication
There are three stages of cell signaling:
Reception – where the target cell detects
a signaling molecule present in the
exogenous environment.
Transduction – the conversion of the signal
to a form that can bring about a specific
cellular response, we can amplify here.
Response – the specific cellular effect
brought about by the signaling molecule.
Reception: a signal molecule (ligand) binds to a receptor protein (receptor), causing it to change shape. The interaction between a ligand and receptor is highly specific. A conformational change in a receptor is often the initial stage in the transduction of a signal. Receptors are found in two places; Intracellular proteins are found inside the plasma membrane in the cytoplasm or nucleus. The signalling molecule must cross the plasma membrane and therefore must be hydrophobic (for instance the steroid hormone testosterone), or very small (Nitric Oxide). Or Cell-surface proteins are embedded in the plasma membrane, and these receptors bind to water-soluble ligands.
Transduction: cascades of molecular interactions relay signals from receptors to target molecule in the cell. Enzymes called protein kinases . These proteins cause an amplification of the signal, thus exaggerating the
Response: cell signaling leads to the regulation of cellular activities.
Increase in cellular complexity=
increase in cellular
specificity=increase in # of
cells=increase in cell to cell
communications