evolution of eukaryotic cells starting from prokaryotic 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 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!