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Lecture 6

Biology 1002B Lecture Notes - Lecture 6: Electron Acceptor, Oxidative Phosphorylation, Electrochemical Gradient

Course Code
BIOL 1002B
Tom Haffie

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Lecture 12 Outcomes:
Factors driving development of aerobic cells
- cyanobacteria possessed the ability to split water, which put oxygen in the atmosphere (very
positive redox potential), therefore O could be used as the terminal electron acceptor (which
lead to aerobic respiration, oxidative phosphorylation)
- aerobic organisms (exhibiting oxidative phosphorylation) make way more ATP than anaerobic
Identify the paradox for why prokaryotes are biochemical complex don't develop
morphological complexity.
- prokaryotes have been around for a very long time therefore it must be a non-temporal
- they can’t support junk DNA to use as a playground for evolution (because of the energy
Relationship between surface area and volume as cells get larger
- As the cell gets bigger, the surface area to volume ratio decreases
- however, since oxidative phosphorylation occurs on the membrane there won’t be enough
surface area or oxphos units (ETC) to produce enough energy to support the greater
Basis of the Proton Motive Force (PMF)
- a proton gradient builds up across a membrane (due to the difference in concentration of H+)
- gradient can be used to synthesize ATP
- The difference of H+ across the membrane causes a concentration and charge difference
- the energy associated with the gradient across the membrane can be calculated (measured
in mV (millivolts))
Relationship between chemiosmotic membranes (units) and need for genes to code for
its proteins
- DNA rings the cell because a fundamental aspect of the ETC, whether its photosynthetic or
respiratory is that some proteins breakdown fast, therefore they need to be replaced fast
- there is an advantage to keeping the genes that code for the proteins that degrade easily
close by
- More chemiosmotic units = more gene copies
Genome size relationships between E. coli, Epulopisculium and Eukaryotes
- Eukaryotes have larger genomes (average 100x) because it isn’t constraint by the amount of
ATP it produces (it produces a lot) therefore the genome can be larger
- difference in mean genome size between prokaryotes and eukaryotes is quantified in terms of
energy available per gene (the cost of expressing the gene)
- in bacteria, all of energy is put into maintaining DNA, energy is used to energetically support
the cell
- Epulopisculium has enough SA (& therefore oxphos units) so it could be larger, but to support
every one of the oxphos units it requires many more copies of its genome near the
membrane (because the proteins on the membrane degrade fast) it is very costly
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