1.5 : The Origin of Cells Flashcards
what is spontaneous generation?
the belief that cells could rise spontaneously.
what is evolution?
the processes that have transformed life on earth from its earliest beginnings to the diversity of forms we know about today, of all living and extinct organisms.
what did Pasteur’s investigation disprove & how? & example?
Disproved spontaneous generation, by proving that there are spores of microorganisms in the air –> & when these reach favourable conditions, they germinate –> giving rise to large populations of microorganisms by cell division.
–> when nutrient liquids become cloudy –> nutrient solids grow visible colonies and moulds = a result of cell division of pre-existing cells.
what are the required steps that are required for the formation of living cells from non-living materials?
- synthesis of simple organic molecules (amino acids, sugars)
- assembly of these molecules into polymers (amino acids to proteins, etc)
- development of self-replicating molecules (nucleic acids = nucleotides)
- retention of these molecules within membranous sacs= internal chemistry developed (different from surrounding environment)
what are the main elements that make up living things?
carbon, hydrogen, oxygen (some nitrogen, phosphorous, sulphur & additional elements)
how did S.L. Miller & H.C. Urey investigate how simple organic molecules may have arisen from ingredients present on earth before life? what does this confirm?
- by using a reaction vessel in which particular environmental conditions could be replicated –> used electromagnetic energy to generate strong electric sparks (simulating lightning) –> passed through mixtures of different gases (methane, ammonia, water vapour, etc) for a period of time –> all gases were cooled down as the spark went around –> amino acids (component of cell proteins) was formed & other compounds (nucleic bases, simple polymers)
- confirmed that organic molecules can be synthesised outside of cells, in the absence of oxygen.
in the assembly of polymers of living things, what type of reaction occurs?
condensation reaction = anabolic –> building up of things = endergonic reaction - requires energy.
as no enzymes were present before, what type of environment was necessary?
need an environment with high heat and pressure.
–> allowing molecules to move around & vibrate a lot –> increased chance of collisions between molecules (due to absence of enzymes).
what is the advantage of sugars being present near volcanoes or lava flow?
- a lot of sulphur, phosphorous, etc gases are present in these environments –> elements necessary for the build up of living things.
- has ideal environment –> volcano = gas enclosed in rock –> temperature will rise, leading to an increase in pressure.
what does the evolution of life from a mixture of polymers and their monomers require?
- a self-replication system
- the ability to catalyse chemical change.
what functioned as an enzyme and DNA before life, when these weren’t present?
RNA –> can function as an enzyme –> assume that RNA combined roles of ‘information molecules’ and ‘enzymes’ in the evolution of life.
–> short RNA molecules would’ve functioned as replication system & enzymes (catalyst) = but the catalytic activity of RNA is lower.
how are microspheres formed?
when more & more lipids are present (hydrophobic) –> bilayers are formed –> when there is a gap present somewhere in the lipid bilayer –> prebiotic soup enters
–> forms membrane systems with distinctive internal chemistry (different from external) –> microsphere formed. (not yet a cell)
what needs to generate for a microsphere to become a prokaryote?
- enzymes generation of a circular chromosome that is a helical sequence of nucleotides (RNA or DNA)
- generation of cell wall (some prokaryotes)
- generation of enzymes (RNA doesn’t conduct this function anymore due to evolution)
what benefit did microspheres with proteins that developed enzymes have in the past?
they thrived better in the past –> had faster catalytic activity.
what occurs when prokaryotes form into eukaryotes & how do these form? (the endosymbiotic theory)
(nucleus, nuclear membrane, organelles needed)
- formation of nucleus : chromosomes gathered in a sac of infolded plasma membrane until a nuclear membrane is formed.
- organelles formed : may have ingested (and not digested) other prokaryotes with food –> these may have survived inside the host cell after being engulfed –> may have happened with mitochondria & chloroplast (seem to have their own DNA).
