A2.1 Origin of cells Flashcards
what were the conditions on Early Earth
molten rock surface
as it cools down, released gases form atmospher( high amounts of carbon dioxide)
greenhouse gases lead to higher temperatures
lack of oxygen and ozone = high amounts of UV radiation
UV radiation = damages DNA/ causes mutation
lower levels of UV allowed life to exist
what would the conditions on Early Earth lead to
it may have led to carbon compounds being formed spontaneously
what would high levels of UV radiation may have led to
bases of nucleotides are highly efficient at reducing the harmful effects of UV, meaning RNA has more of a chance to form chains
possible that UV was a selection factor that drove processes forward
what are the three principles that define life
evolution through natural selection(ability to reproduce and vary genetically)
life forms are contained and separate from, but in communication with their environment
chemical and physical machines that receive/respond to info
what would happen if life were to evolve with different liquids
they would be fundamentally different
what is the flaw with only having knowledge of earth life
unable to distinguish which properties of life on earth are unique and which are needed to qualify as life
why is it hard to classify viruses
they exhibit some features of life when present on a host cell but otherwise, do not respond to stimuli
what are the common features of cells
stable, partially permeable membrane that surrounds cell compounds
genetic material that can be passed onto newly formed cells, and control functions of cells
metabolic processes that allow energy generation, enabling growth, maintenance and reproduction
what would the formation of living cells have required
synthesis of simple organic molecules
assembly of these molecules into polymers
development of self replicating molecules
retention of these molecules within membraneous sacs
what are the three theories for the origin of life
protocell first
gene first
metabolism first
explain the theory of life that states protocell came first
a cell like compartment that had basic metabolism but lacked developed genetic systems
divided into daughter cells that eventually evolved until acquiring a genetic system
explain the theory of life that states gene first
RNA or DNA arose spontaneously and were capable of replication
they evolved throuhg natural selection, formation variants with cell membranes leading to metabolism
explain the theory of life that states metabolism first
self sustaining system of simple reactions, capable of feeding on nutrients and energy arose spontaneously, perhaps on mineral surface. eventually evolved cells and genetic systems
theory is favored because functions of life require high amounts of energy
what is the evidence for the origin of carbon compounds
found that amino acids were formed naturally with other compounds
shows us that organic molecules can be synthesized outside cells, in the absence of oxygen
what is polymerization
when monomers combine chemically to produce a larger molecule
what is required for polymerization to take place in the absence of cells and enzymes
concentration of biologically important molecules such as monosaccharides, amino acids and fatty acids
clay also show to promote polymerisation
where could polymerisation have taken place
may have happened in water close to volcanoes where its hot, pressure is high and gases being vented are rich in sulfur etc.
why are fatty acids likely to have formed the components of cell membranes
they are amphipathic( polar and non polar ends)
meaning they form monolayers on water
why are the formation of microspheres/vesicles important
systems were able to develop a chemical environment different from their surrounding
what is required for the evolution of life from a mixture of polymers and their monomers
a self replication system
an ability to catalyse chemical change
what is the other possible function of RNA other than an information molecules
possible it functioned as an enzyme
what is the RNA world Hypothesis
the earliest life forms used RNA as genetic material and enzymes
only after evolution, did DNA take over as the genetic material
What are ribozymes
RNA molecules that have catalytic properties
Why is RNA though to play a central role in the origin of life
Due to its unique potential as a carrier of genetic info and as catalysts
How can DNA be used as evidence for similarities and differences between species
the more similar the genes the more closely related two species are
What is LUCA
the last universal common ancestor
an organism that existed 4 billion years ago which we all evolved from
Why may other organisms that lived as the same time as LUCA may have gone extinct
due to competition for resources
How can the age of LUCA and other such organisms be predicted
through genomic analysis, where the average time for mutations to take place is estimated
what characteristics is LUCA assumed to have
anaerobic
CO2 fixing
H2 dependent
N2 fixing
thermophilic
Where are the fossils of first life most likely to be
in rocks near deep sea, hydrothermal vents
