A2.1 Origin of Cells Flashcards
why was the Earth formed?
gravity caused dust and gas to come together
describe the pre-biotic atmosphere
only traces of oxygen because it reacted with other elements; methane concs higher bc of intense volcanic activity and meteorites; CO2 concs higher bc of volcanic emissions
why were temps higher than they are now?(4)
high concs of CO2 and CH4 which are heat-trapping greenhouse gases; comet and asteroid impacts; the ozone layer that now protects us wouldnt exist bc of lack of oxygen, without the layer more solar UV would have penetrated to earth’s surface; more lightening triggering other chemical processes
where would carbon compounds be formed?
specialized environments eg hot springs on land or hydrothermal vents in oceans
what would carbon compounds have formed?
droplets of water in the atmosphere, creating an ORGANIC AEROSOL HAZE which would have deposited into lakes/oceans creating a ‘soup’ of carbon compounds
what happened as organisms came about?
they increases oxy conc and decreased CO2 conc so ozone layer formed giving protection against UV + greenhouse effect was reduced
cells can be considered as…
the smallest units of self-sustaining life
what are the 3 components of cell theory?
all living organisms are composed of one or more cells; the cell is the most basic unit of life; all cells arise from pre-existing cells by division
what are the functions of life(Mr H Gren)
metabolism, response, homeostasis, growth, reproduction, excretion, nutrition
which developments are needed for the origin or cells?
catalysis, self-assembly(carbon compounds eg amino acids need to assemble to form polymers), compartmentalisation(membrane to enclose cell contents), self-replication
Miller-Urey experiment
passed steam through CH4, H, ammonia simulating earth’s atmo, used electricity to mimic lightening, found amino acids and carbon compounds could be formed, theorised these would then form polymers using energy from deep sea vents and trigger mechanisms for inheritance before becoming enclosed in a membrane to form a cell
strengths of miller-urey experiment
repeatable-similar experiments have shown a diversity of carbon compounds can form spontaneously in an atmosphere lacking oxygen
weaknesses of miller-urey experiment
miller and urey probs got some conditions wrong-pre-biotic Earth had more CO2 and N2 and less NH3 and CH4 and less lightning
what is a vesicle?
small droplets of fluid, enclosed in a membrane
what are exosomes?
extracellular vesicles which some cells produce
what does the membrane of vesicles consist of?
mainly phospholipids, experiments show that bilayers spontaneously form stable spherical structures
what would have happened if phospholipids were part of the ‘soup’ of carbon compounds?
they would have self-assembled into bilayers and vesicles would have likely formed but movement of pilar in and out would have been limited by hydrophobic membrane core so would have developed own internal chem(cell-like)
what can RNA do?
store info like DNA but is self-replicating and can act as a catalyst
what do some viruses use as genetic material?
RNA which supports theory that RNA could have been used before genes of DNA evolved
LUCA
last universal common ancestor, the hypothetical organism from which all life on earth is believed to have descended
what is convergent evolution?
when it’s possible for similar structures to evolve in organisms that don’t have a recent common ancestor
conditions for luca?
would have used RNA to store genetic info and catalyse chemical reactions, would have been highly resistant to extreme environments
evidence for luca?
universal genetic code in all cells, same building blocks for RNA and DNA in all cells, common molecular processes in all cells
what is an emergent property?
characteristics of an organism not evident on a cellular level created by interactions between cells
