A2.1 origin of cell Flashcards
primordial soup
early oceans of earth, rich in simple carbon based compounds
when did life originate
between 3.5-3.9 billion years ago
conditions on early earth
- high surface temperatures (75-95oc)
- entire surface of earth was water
what happened when asteroids bombarded earth
comets and asteroids went to earth which brought water and other compounds to planet
methane and ammonia gases where released due to collisions and volcanic erruptions
what was the atmosphere composed of
methane and ammonia formed most of earths atmophere + water vapour and higher co2 concentration
what caused the extreme weather in early earth
no ozone layer due to lack of oxygen.
inner coe was much hotter and increased motion
this meant smaller protective magnetic fiels= more cosmic solar radiation
necessar percurser to the orgin of life
formation of simple carbon based compounds- percurser to complex molecules then organic molecules which provide the structural and functional components for cells to survive
what made the early earth have a reducing atmophere
lack of oxygen, high porportions of reducing gases like methane and ammonia
what is one hypothesis for the origin of cells
spontaneously
conditions of pre biotic earth summary
- reducing atmophere (no o2, no co2, high level s of ammmia and hydrogen ions)
- very high temp
- high volcanic erruptions
- hugh UV
- high lighting storms
- high asteroid
what are the steps of spontaneous origin of cells hypothesis
1) inorganic compounds (H2, NH4, H20, co2)
2) organic compounds monomers- simple amino acids
3) complex organic molecules (polymers)- proteins, RNA, LIPids
4) self replicating polymers
5) polymers in vesicles
6) first cells
how does it go from inorganic compounds to organic compounds
spontaneous formation of simple organic compounds from catalysts of energy coming from lighting and high temp
how does it go from organic compounds (monomers) to organic compounds (polymers)
condensation
how does it go from complex organic polymers to self replicating polymers
polymers such as rna ( nucleotide made of sugar phosphate) have catalytic characteristics- they can act as an enzyme called a ribozyme and catalyse their own replication
how does it go from self replicating polymers to polymers in vesicles
polymers where compartmentalized into vesicles ( were made of fatty acids instead of phospholipids) form into a spherical bilayer that encloses space. hydrophobic tails of bilayer tucked together form micelles that then evolved into vesicles
how did it go from polymers in vesicles to first cells
vesicles evolves using phospholipids and integral proteins
evidence for spontaneous formation of organic monomers from inorganic compounds
miller urey experiment - simulated ancient water cycle
evidence that first genetic materia comes from RNA first hyphothesis
- complex protein, carbohydrates and rna was found in deep sea thermal vents. the high heat of enviorment + reducing inorganic molecules allowed condensation
- self replicating polymers where seen happening with rna. rna countains genetic code with bases and issingle stranded molecule which increases efficiency when compared with dna. rna has catalystic property as it can act as a ribozyme, catalysing specific reaction like protein synthesis
process of miller urey experiment
1) liquid water was placed in flask with heat source, simulated ancient ocean conditions with high temperature and presence of volcanic eruptions
2) simulation of pre biotic atmophere- reducing, water vapour was mixed with methane, ammonia, hydrogen, electrical discharges
3) mixture allowed to cool down (simulate water condensation)
4) after one week the mixture turned into brown liquid tested and found to have same amino acids and complex oil of hydrocarbon
LUCA
last universal common ancestor- single celled autotrophic micrope with an rna genome that existed billions of years ago
evidence for LUCA
the genetic code is universally shared by all living organisms-it uses the same nucleotide triplets, codons to code for same amino acids
this is since the genetic code has been conserved as it is essential for the transmission of genetic information
