Origin Of Life Alan McCarthy Flashcards
Biogenesis
Living matter arises from living matter
Abiogenesis
Origin of life from inorganic substances
Spontaneous generation
Mice from wheat and flies from meat where both once believed
How did life come about
Once in a dramatic event
OR
Evolved gradually from complex chemistry
Autotrophs
Use CO2
Heterotrophs
Use organic sources of carbon
The inheritance problem
DNA - RNA - Protein
Requires proteins and RNA for replication and a metabolic component
Stromalites
Early traces of life but could be fractal frauds stromalites could be abiotic although it was said that they condition photosynthetic Cyanobacteria from layered mounds of rock
Location of the origin of life
Groundwater - concentrated and ionising radiation as energy source no ozone so photochemical destruction of biomonomers become concentrated
Superoxides and free radicals are unstable and highly reactive
Extraterrestrial - amino acids and nucleotides mag have been carried on meteorites
Polymerisation of biomonomers into biopolymers needs ATP and concentration eg groundwater pools or clay and rock surfaces
Hydrothermal vents
Aggregates
Early forms of cells such as coercatives , proteinoids and liposomes
Very fragile
Possible stages of the first cell
Prebiotic - substrates turning into products with a catalyst
These products may have formed primordial soup creating abprotocell (aggregates) but still metabolism is needed to create the first cell and emergence of life
Metabolism
The chemical processes that occur within a living organism in order to maintain life
The first cells
Heterotrophic organic carbon
Fermentation no oxygen in the environment lactic acids formed
Modern / later cells
Autotrophs use CO2 photosynthetic
Aerobic redox cycle
What happened for oxygen to become part of the environment
Bacteria lack a detoxification mechanism
Use oxygen to respire producing an oxidising environment, ‘ozone’ layer and carbon cycle
Lots of oxygen present in environment
Free radicals
With unpaired electrons are highly reactive and destructive they were mopped up by superoxide dismutase and converted to hydrogen peroxide catalysed onto water and oxygen
Hydrothermal vents
Constant environment
Rich in chemicals and CO2
Continuous energy source
Protected environment
BUT
are they too hot
The first cells would’ve been autotrophs not heterotrophs and hyperthermophiles
Mitochondrial DNA
Strong sequence and gene similarities to bacterial DNA
Rickettsia- obligate intercellular parasites that have the most similar DNA sequences to mitochondria
Hydrogenosome
Have no DNA or mitochondria
However eventually one with DNA was found and when sequences it was found to have relations to mitochondria
Mitosomes
Mini mitochondria occur in anaerobic Protozoa and have functions in anaerobic respiration suggesting previously they may have had a role in this
Hydrogen hypothesis
Symbiosis between a archaea and a eubacteria the bacterium secretes hydrogen and CO2 and the archaea lives on these and generates methane becomes heterotrophic
Archaebacteria
Thermoacidophiles
Extreme halophiles
Methanogens
Abnormal ribosomes
Atypical cell wall
Atypical lipids ether based not Ester based
Phenetic
Based on observed characteristics
Phylogenetic
Based on evolutionary history
Phenotype
Detectable characteristics of an organism
Gentype
The sum total of genetic information in an organism
DNA as a fossil record
DNA is a living fossil record however the feasibility of sequencing and rate of change need to be taken into account
What is needed is short sequences conserved sequences and universal sequences
16S RNA
5 kingdoms
Monera - bacteria Protista Fungi Plants Animalia
Woese
Unrooted tree 3 kingdoms Eubacteria Eukaryotes Archaebacteria
Lokiarchaeota
Most closely related to us
Microbial genomes
First archaebacteria sequence showed metabolism genes allowing replication of genes almost eukaryotes like
Suggests a common ancestor
