"PROKARYOTES"
As we discussed in class, the term prokaryote really is not so valid anymore, since
we can now examine these organisms at the molecular level, and can describe them in
positive terms, not by what they are not. Nevertheless, you are expected to understand
this and other outdated concepts because the science education establishment is afflicted
with a condition known as paradigm paralysis. For those of you with the Princeton
Review study guide, you can find what the science education gurus expect you to know.
I'm jaded and cynical, so for the sake of that SAT II, stay close to your text and the study
guides.
Prokaryotes - (synonym = monerans - also a ridiculously outdated term) The first life
forms on the planet.
- All prokaryotes are unicellular, though some form colonies with specialized
cells, which puts them on the borderline of being multicellular.
- Prokaryotes lack a nucleus (that's what prokaryote means), and other subcellular, membrane-bound organelles.
- Oxidative respiration in aerobic bacteria utilizes the plasma membrane to
create the necessary proton gradient. Remember, no mitochondria.
Cell structure - page 160-161
Reproduction - binary fission, page 318-319
"Chromosomes" - 13.3, page 347
Classification - page 483
Ecological roles
- Photosynthesis; cyanobacteria
- Nitrogen cycle: fixation;free- living and symbiotic in plant roots;
denitrification; ammonification
- Decomosition
- Mutualistic symbiotic relations; too numerous to list
- Pathogens of animals and plants
- Unknown (there are a lot of microbes out there, and one in particular might be
the most abundant life form on the planet, yet we don't understand its role in
the biosphere. The same is true of many Bacteria and Archaea
Structural features
- cell wall; peptidiglycan; gram positive and gram negative (Bacteria only)
- flagella
Mechanisms for genetic exchange (sexy time) - conjugation, transformation,
transduction. These mechanisms are collectively referred to as Horizontal or Lateral
Gene Transfer (HGT or LGT). This is opposed to the vertical gene transfer that results
from direct inheritance.
- conjugation = direct transfer of partial genome between cells
- transformation = uptake of discarded genes from the environment
- transduction = viruses carry genes from one cell to another just like mosquitos
carry West Virus and Malaria.