1.5 Origin of cells

Miller-Urey experiment

The non-living synthesis of simple organic molecules has been demonstrated by the Miller-Urey experiment

Conditions in the Miller-Urey experiment

Water was boiled for high temperatures.
A variety of gasses were added but no oxygen.
Electrical discharge (lighting and energy source)

Conditions of initial formation of life

Reducing atmosphere and high temperatures (>100) or electrical discharges to catalyse chemical reactions

Biogenesis

the division of pre-existing cells

Pasteur's experiment

Broths were stored in vessels that contained long tubings (swan neck ducts) that did not allow external dust particles to pass
The broths were boiled to kill any micro-organisms present in the growth medium
Growth only occurred in the broth if the flask was broken open, exposing the contents to contaminants from the outside
From this it was concluded that emergent bacterial growth came from external contaminants and did not spontaneously occur

Evidence embosymbiosis

MAD DR.

Membranes (double membrane bound)
Antibiotics (susceptibility)
Division (mode of replication)
DNA (presence and structural composition)
Ribosomes (size)

Endosymbiotic theory

The evolution of mitochondria and chloroplasts. Before mitochondria and chloroplasts were organelles in a cell, they were free prokaryotic cells that were absorbed by eukaryotic cells.

Current knowledge

Volatile atmosphere, methane, and lightening.
These conditions are no longer on earth, all present cells come from pre-existing cells.

First cell

Prokaryotic (simple)

How do we know that all living things came from one cell

All living things perform the same functions.
All living things have DNA with a similar structure, who's code make the same amino acids.

How did eukaryotes evolve?

1. About 2 billion years ago, a eukaryotic cell engulfed a heterotrophic bacterial cell.
2. The eukaryote and prokaryote formed a symbiotic relationship.
3. Over time that bacterial cell underwent changes to eventually become a mitochondria.