What is the hypothese of “Spontaneous generation”?
Life was appearing from non-living things at all time
What is the first scientific hypothese (pre-biotic evolution) of Oparin and Haldane (1920’s)
Like the theory of evolution but with molecules
- stable/unstable
What are 3 mechanisims that can explain how monomers have formed?
- Delivery from space
-> meteorites colliding with earth containing simple sugars, amino acids and nucleotides - Chemical reactions at hydrothermal vents
-> hot water with a high concentration of minerals hits cold ocean water, can form amino acids and other organic molecules - Atmospheric reactions
-> tested by the Miller-Urey experiment
What was the Miller-Urey experiment? What were they testing? What was their results?
- were testing Oparin and Haldane’s “pre-biotic evolution”
- testing if lightning could have made organic molecules on earth
RESULTS
- large organic molecules used by life today could form under pre-biotic conditions
- lightning caused reactions between atmospheric gases, forming amino acids and other organic compounds
- they could not form if O2 was present in the reaction chamber
What are some steps required towards the creation of the first cell?
- Organic molecules would have to accumulate in the oceans
would have to have a shelter from the sun’s UV rays - Organic molecules would have to become concentrated in one area and react with each other
clay: made of charged molecules
charged clay molecules may have attracted ions and charged organic molecules to the same location
Iron-sulfur world hypotheisis:
- adherence of organic molecules to iron-sulfur compounds in hypothermal vents. -> Accumulation in cell-sized indentatoins in the rock
- Basic cell structures would have to form
What is the type of the first cell? And what does it contain?
- a protocell (LUCA)
- RNA as genetic material since it can replicate itself when it is a ribozyme ( acts like an enzyme) because DNA can’t replicate itself
- a membrane: microspheres of lipids and proteins that can form on their own and absorb molecules
What is the order of parution of the first 3 types of cell?
- Prokaryotic, anaerobic
- Prokaryotic, anaerobic, photosynthetic
- Prokaryotic, aerobic
How was the first cell to evolve from the protocell like?
Prokaryotic and anaerobic.
Anaerobic: no oxygen on early earth -> not efficient (lots of food required)
How was the second cell to evolve from the protocell like? (evolved from the prokaryotic and anaerobic cell)
Prokaryotic, anaerobic and photosynthetic.
Photosynthetic: trap the energy from sunlight and store it in the form of food.
Why were aerobic metabolism “created”?
Oxygen gas was toxic to many species back then because they had evolved without it.
As more and more prokaryotic, anaerobic, photosynthetic cells created oxygen, it lead to an oxygen crisis.
What was the effect of the oxygen crisis on cell types?
-> some types of cells went extinct
-> some types of cells evolved:
- adapted to new habitats that were always without oxygen
ex: prokaryotes in deep rocks
- adapted ways of detoxifying or using oxygen. -> aerobic metabolism
ex: eukaryotes, some prokaryotes
What does the endosymbiont hypothesis explains?
How some organelles found in eukaryotic cells today may have evolved.
What is the first eukaryotic organelle to have evolved according to the endosymbiont hypothesis? And how?
The mitochondrion
1. a large prokaryotic cell -> swallowed small prokaryotic cell but X digested it
2. over millions of years, small cell evolved into mitochondria
3. gave rise to the first pre-eukaryotic, aerobic cell
In the creation of the mitochondrion, what are the benefits for the small and for the big cell?
Small:
- protection
- ample food supply
Large:
+ energy from the same amount of food
What is the second eukaryotic organelle to have evolved according to the endosymbiont hypothesis? And how?
The chloroplast
1. A large pre-eukaryotic cell -> swallowed small prokaryotic cell but X digested it.
2. Over millions of years -> small cell evolved into chloroplast
- gave rise to eukaryotic, photosynthetic and aerobic cells
- gave rise to some kinds of protists, and then plants
In the creation of the chloroplast, what are some advantages for the small and for the big cell?
Small:
- protection
- (but not ample food supply (already full))
Large:
- makes its own food
