1: Origin of Life Flashcards
what was initial atmosphere made up of
methane
CO2
ammonia
nitorgen
when did earth cool enough to allow water to condense
4.2 B yrs ago
why sedimentary rock used as indicator of life
forms from bodies of water
can find ‘microfossils’ in there
how is isotopic analysis used as evidence for microbial life
Carbon12 and Carbon13 metabolised differently
Carbon12 is preferred
so if carbon detected in rock, then we can know its from microoraganism since it will have lots of carbon 12 and less carbon 13
why is RNA preferred over DNA as candidate for origins for life
- RNA only single strand, so can fold into distinct shapes
- RNA molecules are involved in many cellular processes
- RNA can self replicate
- they have enzymatic activity (ribozymes)
in an anaerobic environment, what kind of metabolism did early cells have
H2 used as a fuel
dissociation of H+
via primitave hydrogenase
provided gradient across membranes
powers ATPases
what is phylogeny
evolutionary or natural history of organisms
using nucleotide sequence comparisons
4 things that make a ideal candidate gene to sequence for phylogenetics
- must be present in all organisms of interest
- not laterally transferrered
- appropriate level of sequence divergence (so how different sequences can be between themselves)
- large enough to contain a record of historical informantion
what is most useful gene sequence for phylogenetic reconstruction
16s rRNA gene
what did carl woese propose after investigating phylogeny
3 domains of life
bacteria, archaea and eukarya
chemoorganotrophs
an organism that obtains energy from the oxidation of reduced ORGANIC compounds
chemolithotrophs
an organism that obtains energy from the oxidation of reduced INORGANIC compounds
phototrophs
an organism that uses energy from sunlight to synthesize organic compounds for nutrition.
what’s the organic e- acceptor
O2
PMF
proton motive force
basiically refers to the proton gradient, in this situation it allows production of ATP
why is more energy conserved in aerobic resp
O2 is at bottom of e- tower
so e- drop down a further distance
conserving more energy as they go
if no O2, what alt e- acceptors are there
inorganic nitrogen and sulphur
CO2
iron compounds
in this, less energy is conserved than when O2 is the e- acceptor
what are 2 mechanisms of ATP synthesis in chemoorganotrophs
respiration
: oxidative phosphorylation
more ATP produced
fermentation:
substrate level phosphorylation
high energy bonds broken in ‘energy-rich’ intermediates
which provides energy for ATP production
but less is produced
autotrophy
uses CO2 as its carbon source
heterotroph
obtains carbon from organic compounds
2 types of phototrophs
anoxygenic
(get their e-/reducing power from chemicals e.g. H2S)
oxygenic
(get their e-/reducing power from H2O producing O2)
which type of phototroph appeared first
anoxygenic
oxygenic ones (e.g. cyanobacteria) lead to great O2 event
