Origin of Cells

what was probiotic earths atomosphere mostly composed of

• nitrogen

• CO2

• water vapor

• methane and hydrogen

• lightining

what was not in Earth's atmosphere

OXYGEN NOR OZONE

• first introduced by photosynthesis

due to high CO2 and no ozone what were the conditions like

• UV from sun was intense

• CO2 kept temperatures high because of a increased greenhouse effect

With all the conditions on Earth what did Oparin and Haldane hypothesized would cause

spontaneous generation of organic compounds

• overtime become more complex- self replicating strucutres and cells

cell theory

• all living things are made of cells

• cells are the smallest units of structure and function

• new cells come from pre-existing cells

CELLS ARE THE BASIC UNITS OF LIFE

all living organisms

• have at least 1 cell

• metabolize

• maintain homeostasis

• respond to stimuli

• reproduce

• grow and develop

• contain genetic information in the form of DNA

why are viruses not alive

• have genetic information as DNA or RNA

• but no: homeostasis, metabolism, response to stimuli, no growth, no self-replication

origin of cells included

• catalysis

• self-replication of molecules

• self-assembly

• emergence of compartamentalization

Miller Urey Experiment

• Hypothesis: life spontaneously generated on pre-biotic earth

• methane

• water (ocean)

  • vapor

  • condenser (water cycle)

• spark (lightning)

• ammonia

1 week later- water was brown with amino acids and other complex organic molecules were produced

Showed: some of the organic molecules required for life could be spontaneously generated under certain conditions

strenghts vs weakness of Miller Urey experiment

Strength

• modelled pre-biotic earth and atmosphere

• demonstrated molecules could be spontaneously generated under certain conditions

• design easily replicated

Weakness

• debate on actual atmosphere

• not all conditions replicated

• did not produce all organic molecules required for life

metabolism requires

• separation of cytoplasm from enviornment

  • cell membrane made up of phospholipid bilaer

    • ampiathic (hydropho tail, philic head)

      • properties make it form sperical bilayers in aqueous solutions

in experiments similar to Miller Urey

• fatty acids spontaneously formed and made sperical bilayers in aqueous solutions

• hypothesized: first genetic material was trapped within phosopholipid vesicle forming protocell

why RNA first genetic material

• store genetic information

• capable of self-replication

• catalyze reactions

ribozomes

 in the ribosome catalyze the formation of peptide bonds during protein synthesis.

Last Universal Common Ancestor (LUCA)

• most recent common ancestor for all organisms on Earth

• could be other organisms alive at the time but LUCA outcompeted them

• no fossils

• EVIDENCE: all organisms share the same genetic code

• shared genes inherited by LUCA

Bacteria, archaea, eukaryotes

cladistics

analyse change in genetic code to estimate age of common ancestors

LUCA Is about

4 billion years ould

the oldest fossils of cells cyanobacteria are about

3.5 billion years old

we date fossils using

radioactive dating of uranium

molecular clocks

Comparing the number of mutations in genes between species allows scientists to estimate when the two species diverged into separate species.

LUCA evolved near

hydrothermal vents

• rich in organic compounds, such as methane, carbon dioxide, and hydrogen.

  • Experiments similar to Miller and Urey’s show that the building blocks of life, such as proteins and nucleotides can form from these chemicals.

• fossils of cyanobacteria have been discovered from ancient seafloor hydrothermal vent precipitates.

• genes analyzed common ot all 3 domains of life have identified highly conserved genes

  • include thermophilic metabolism, suggesting that LUCA may have evolved in a high temperature environment such as hydrothermal vents.