Biology 1002B Lecture Notes - Lecture 12: Endomembrane System, Noncoding Dna, Chemiosmosis
11 Apr 2017
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The problem with getting bigger for prokaryotes: oxidative phosphorylation units must be on plasma membrane, as cell (sphere) gets bigger, its surface area: volume ration goes down. Plasma membrane surface area not great enough for enough units of oxidative phosphorylation to sustain the increase in volume. Eukaryotes have mitochondria (with gigantic surface area for site of oxidative phosphorylation: no constraint for overall cell size. Bc bacteria have many internalized membranes: some proteins break down fast, and need to be replaced fast. Importance of proximity, want genes required for chemiosmosis to be close by. More chemiosmotic units = more gene copies (prokaryote, thus entire copy of its genome) More energy = can put more energy into maintaining more dna. Have no evolutionary advantage to constrain genome size: gene density: 1000 genes/mb in prokaryotes, 12 genes/mb in eukaryotes. Efficiency needed in prokaryotes (every gene has a purpose)
