Transcript Evolution of Eukaryotic Cells

Evolution of Eukaryotic Cells
Starting from Prokaryotic Cells!
Three Prokaryotic Cells
nucleoid
nucleoid
nucleoid
70S ribosomes
70S ribosomes
80S ribosomes
Krebs Cycle
Calvin Cycle
Glycolysis + Fermentation
ETS + Ox Phos
Light Reactions + Photo Phos
Endomembrane System
Cell Membrane
Cell Membrane
Cell Membrane
Murein Wall
Murein Wall
None (Contractile Vacuole)
Three Prokaryotic Cells
nucleoid
70S ribosomes
Krebs Cycle
ETS + Ox Phos
Cell Membrane
Murein Wall
Typical Bacterial Cell
Murein Wall
Naked Circular DNA genome
70S Ribosomes
Carries out Aerobic Respiration
Enzymatic Glycolysis and Krebs Cycle in Cytosol
Electronic ETS and Ox Phos in/across Mesosomes
Highly efficient ATP production from simple fuel
molecules
36 ATP per glucose
Three Prokaryotic Cells
nucleoid
70S ribosomes
Calvin Cycle
Light Reactions +
Photo Phos
Cell Membrane
Murein Wall
Typical Cyanobacterial Cell
Murein Wall
Naked Circular DNA genome
70S Ribosomes
Carries out Photosynthesis
Enzymatic Calvin Cycle and Condensation Reactions in
Cytosol
Electronic Light Reactions and Photo Phos in/across
Thylakoid Membranes
Highly efficient ATP production
Highly efficient synthesis of a wide range of organic
molecules from CO2
Three Prokaryotic Cells
Archaeon Cell
No Wall (Contractile Vacuole avoids burst)
Multiple protein-bound DNA molecules in
genome
70S becoming 80S Ribosomes
Metabolism by Fermentation Only
Enzymatic Glycolysis and Fermentation
Reactions in Cytosol
Comparatively inefficient ATP production
2 ATP per glucose
Must consume huge amounts of fuel
Highly evolved endocytosis (phagocytosis)-leading to endosymbiosis
Large cytoplasm requires highly developed
endomembrane system from mesosomes
Formation of nuclear envelope to avoid
digesting its own DNA
Transposon system for acquiring/incorporating
more DNA into genome
nucleoid
80S ribosomes
Glycolysis + Fermentation
Endomembrane System
Cell Membrane
None (Contractile Vacuole)
Three Prokaryotic Cells
Wall Loss
Critical Gene Movement
Endocytosis
Binary Fission
Many critical genes moved into the host nucleoid/nucleus of Organelle
The endosymbiont has become an organelle
...no longer capable of independent respiration
The mitochondrion has two bounding membranes
The host vesicle membrane
The endosymbiont cell membrane
Three Prokaryotic Cells
Wall Loss
Critical Gene Movement
Binary Fission
Endocytosis
A critical gene moved into the host nucleoid/nucleus is the
of Organelle
rubisco small subunit
The endosymbiont has become an organelle
...no longer capable of independent photosynthesis
The chloroplast has two bounding membranes
host vesicle membrane and endosymbiont cell membrane
Three Prokaryotic Cells
The fermentation-only archaeon has
taken in a bacterial cell and a
cyanobacterial cell as
endosymbionts
By not digesting them completely, but
removing the cell wall, the
archaeon has gained two gigantic
biochemical pathways: respiration
and photosynthesis
By moving critical genes from each
endosymbiont, using its
transposon feature, the archaeon
has trapped both endosymbionts
as permanent organelles
This is almost a eukaryotic plant cell!
Three Prokaryotic Cells
The archaeon still needs to convert
its endomembrane system into
endoplasmic reticulum
And consolidate the encircling
membranes into a nuclear
envelope
And make its circular chromosomes
linear with telomeres
And finish the evolution of the 80S
ribosomes
It also needs to entrap some
spirochetes for a cytoskeleton and
for a eukaryotic flagellum
The sequence of these steps relative
to the endosymbiont capture is still
being resolved!