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A2.1- origin of cells - Coggle Diagram
A2.1- origin of cells
2
.
Cells as the smallest units of self sustaining life
cells can be multiceullar to unicellular
some multicelluar organisms are dead (skin)
self sustaining
highly ordered state
cells divide to produce more cells
cells can be taken from the body and can be cultured HeLa cells
why organelles arent alive
organelles perform specialized tasks but cannot live independently
mitochondria
: enables cell respiration however it cannot be carried out without proteins
chloroplasts
: carry out photosynthesis but cannot reporduce or mantain homeostasis on their own
approaches to estimate dates of the first living cells and LUCA
Stromatolites
formed by mats of cyanobacteria.
live in shallow sea water
trap sediment
secrete calcium carbonate, which slowly builds rocky layers.
ate to about 3.42 billion years ago.
isotope evidence
low ¹³C/¹²C ratios in rocks formed from biological material.
carbon isotope ratios to detect past life.
3.70–3.85 billion years ago.
Genomic evidence
number of genetic differences between species increases with time.
stimate when species diverged from a common ancestor.
Last Universal Common Ancestor (LUCA) lived about 4.5 billion years ago.
theia impact
Early Earth may have been struck by the planet Theia.
This impact likely:
formed the Moon
sterilized Earth temporarily
Life likely appeared soon after this event
3
.Challenge of explaining the spontaneous origin of cells
cells arise from previous cells through cell division
cell division starts from a zygote
initial theory
:living organisms can be FORMED from nonliving matter
requirements for the origin of cells
catalysis
self assembly
compartmentalization
self replication
4.*
Evidence for the origin of carbon compounds (cc)*
J.B.S haldnae stated that oragnic compounds can be formed when uv acts on water ammonia and co2
appratus
5L flask → mixted methame, hydrogen, ammonia (prebitoic atomsphere)
addd water vapor to mixture by boiling. water in another flask
electrical discharges → lightingn
condenser → cooled substances produced and condensate was retured to flask of boiling water
results
pink after a few days
red after a week
20 amino acids produced
steps
Evaporation: Water was boiled to create water vapor (simulating the ocean).
Gas Mixture: The vapor mixed with methane, ammonia, and hydrogen (simulating the atmosphere).
Energy Source: Electrical sparks represented lightning, providing energy for reactions.
Condensation: A condenser cooled the vapor, recycling liquid water back into the flask.
5
.
spontaneous formation of vesicles by coalescence of fatty acids into spherical bilsyers
vesicls are small droplets of fluid
enclosed in a membrnae
membrane composed of phospholipids
extracellular vesicles are
exosomes
when mixed in water --> forms a bilayer
Hydrophilic head faces outward and is in contact with water
Hydrophobic tails faice inward away from water
bilayers form spherical structrues
polar molecules in and out of these spherical structures would’ve been limited by the hydrophobic membrane core
RNA as the first presumed genetic material
it can store information in the same way as DNA, however is self replicating and can act as a catalyst
Some viruses use RNA as their genetic material, which supports the theory
Viruses with RNA, such as coronavirus have high mutation rates because of the lack of error checking mechanisms
RNA can act as a catalyst can form 3D structures that can undergo precise interactions with other molecules
evidence for a last universal common ancestor
species w same code found to inherit it from common acnsetor
Convergent evolution → similar structures to evolve in organisms that dont have common ancestor ( not the reason for the universal code)
recent common ancestor who have existed is called LUCA
ther forms of life evolved, however the forms became extinct
*1
.
Conditions on early earth and the prebiotic formation of carbon compounds
*
gases accumulated in differenct concentrations
evidence found in rocks
methance conc were high due to volcanic activity and meteroite bombardment. Co2 was high due to volcanic activty
and lack of life
high temperature (ghg)
high energy of UV penetrated earths surface due to the lack of stratopsheric ozone (no o2) providing activation energy for chemical reactions
formation of carbon coompounds in water droplets
hydrothermal vents in oceans
hotsprings on land
once organisms evolved -> O2 conc increase by 20% -> formation of ozone