evolution of eukaryotic cells starting from prokaryotic cells!
TRANSCRIPT
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 CellMurein WallNaked Circular DNA genome70S RibosomesCarries out Aerobic RespirationEnzymatic Glycolysis and Krebs Cycle in CytosolElectronic ETS and Ox Phos in/across MesosomesHighly efficient ATP production from simple fuel
molecules36 ATP per glucose
Three Prokaryotic Cells
nucleoid
70S ribosomes
Calvin Cycle
Light Reactions + Photo Phos
Cell Membrane
Murein Wall
Typical Cyanobacterial CellMurein WallNaked Circular DNA genome70S RibosomesCarries out PhotosynthesisEnzymatic Calvin Cycle and Condensation Reactions in
CytosolElectronic Light Reactions and Photo Phos in/across
Thylakoid MembranesHighly efficient ATP production Highly efficient synthesis of a wide range of organic
molecules from CO2
Three Prokaryotic Cells
nucleoid
80S ribosomes
Glycolysis + Fermentation
Endomembrane System
Cell Membrane
None (Contractile Vacuole)
Archaeon CellNo Wall (Contractile Vacuole avoids
burst)Multiple protein-bound DNA molecules
in genome70S becoming 80S RibosomesMetabolism by Fermentation OnlyEnzymatic Glycolysis and Fermentation
Reactions in CytosolComparatively inefficient ATP
production 2 ATP per glucoseMust consume huge amounts of fuelHighly 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
Three Prokaryotic Cells
Binary Fission of Organelle
Endocytosis
Wall LossCritical Gene Movement
Many critical genes moved into the host nucleoid/nucleusThe endosymbiont has become an organelle...no longer capable of independent respirationThe mitochondrion has two bounding membranesThe host vesicle membraneThe endosymbiont cell membrane
Three Prokaryotic Cells
Binary Fission of Organelle
Endocytosis
Wall LossCritical Gene Movement
A critical gene moved into the host nucleoid/nucleus is the rubisco small subunit
The endosymbiont has become an organelle...no longer capable of independent photosynthesisThe chloroplast has two bounding membraneshost vesicle membrane and endosymbiont cell
membrane
Three Prokaryotic CellsThe 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 CellsThe 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!