LIFE! (A BRIEF snapshot)
HTTP://WWW.PBS.ORG/WGBH/NOVA/EVOLUTION/ORIGINS-LIFE.HTML
Atmospheric Stuff of LifeCoacervates
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