Proterozoic eon - Proterozoic eon Eukaryote origins The...

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Proterozoic eon Eukaryote origins The main difference between a eukaryote cell and prokaryote cell is that prokaryote cells lack a nucleus to contain its genetic information, a nuclear membrane. - eukaryotes are generally much larger than prokaryotes - has a much more complex interior generally made up of the endomembrane system; nutrient exchange within the cell o directly related to the supply (surface) and function(volume) ratio Small cells have more surface area and less volume, easier to supply the cell with nutrients Large cells have small surface area but more volume, has problems to supply the volume fast enough This lead to infolded membranes to increase surface area - For eukaryotes which are the larger cells, it did this with its genetic information, creating a nuclear membrane to contain and increase surface area within the cell; the nucleus o Nucleus surrounded by a nuclear envelope, because its invaginated membrane, it has an inner and outer component and two bilipid layers. o Selectively permeable for transfer of genetic code; mRNA and such RNA processed (transcripted) in the nucleus than leaves and gets (translated) by the ribosomes outside the nucleus into proteins Explains why original transcript from DNA may have altered; longer process before being translated (must go through nuclear membrane go through procedures, etc, before being translated into protein) - Prokaryotes don’t have a nucleus and so the process takes less time; everything happens in the cytosol (cytoplasm) - The endomembrane also consists of the smooth and rough endoplasmic reticulum - Other important organelle was the mitochondrion, the power plant of the cell. o Originally eukaryotes relied on anaerobic metabolism o Mitochondrion allowed aerobic respiration o At some point in time, a eukaryote cell ate a bacterium but it didn’t die, instead creating a symbiotic relationship; helping each other out The cell provided 3-carbon pyruvate, the bacterium provided high energy ATP through electorn carriers like NADH o This theory is supported by many observations The unique DNA Many attributes of a bacteria o The mitochondrion has two membranes as well, allowing for more surface area
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o Its considered a chemoorganoheterotroph; uses C molecules to create ATP - The endomembrane system, mitochondria, and organelles help give a variety of specialized functions by the cell. Evidence for endosymbiosis Endosymbiosis is shown in the case of mitochondrion but also in some other examples, like the chloroplast (plastid) in plants. - Proof that the mitochondria was an example of endosymbiosis between a bacterium and a simple eukaryotic cell o Double bilipid layer First layer was the membrane of the bacterium Second layer was the membrane that the eukaryote cell used to engulf the bacterium o Has its own DNA It is very much similar to bacterial genome
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This note was uploaded on 09/09/2011 for the course BIO 1130 taught by Professor Fenwick during the Fall '08 term at University of Ottawa.

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Proterozoic eon - Proterozoic eon Eukaryote origins The...

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