lecture 9_tourofcell

lecture 9_tourofcell - Cells: The Working Units of Life How...

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1 Cells: The Working Units of Life Why are cells small and sub-spherical? Biological and geologic history are closely intertwined Fossilized mats of prokaryotes 2.5 billion years old mark a time when photosynthetic How Ancient Cells Changed the Planet… time when photosynthetic bacteria were producing O 2 that made the atmosphere aerobic These fossilized mats are called stromatolites (=bedrock) Planet Earth formed some 4.6 billion years ago Life began on a young Earth EARLY EARTH AND THE ORIGIN OF LIFE The early atmosphere contained H 2 O , CO , CO 2 , N 2 , and possibly some CH 4 , but little or no free O 2 Volcanic activity , lightning , and UV radiation were intense Fossilized prokaryotes date back 3.5 billion years Pre Cambrian bedrock
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2 Life may have developed from nonliving materials as = 500 million years ago Earliest animals ; diverse algae Earliest multicellular eukaryotes ? Earliest eukaryotes rs ago early as 3.9 billion years ago Accumulation of atmospheric O 2 from photosynthetic cyanobacteria Oldest known prokaryotic fossils Origin of life ? Formation of Earth Billions of yea Small organic molecules must have appeared first This probably happened when How did life originate? This probably happened when inorganic chemicals were energized by heat , lightning or UV radiation Stanley Miller’s fantastic experiment… 1953: Miller’s Hi : amino acids and organic molecules could have been generated on a lifeless Earth Water vapor CH 4 Electrode Condenser Cold The Primitive Atmosphere: H, CH4, NH3, H2O lightning Stanley Miller’s experiment water Cooled water containing organic compounds Æ amino acids, sugars, nucleotide bases Sample for chemical analysis H 2 O Warm water: primitive sea H 2 O CH 4 NH 3 H 2 H 2 O amino acids, sugars, nucleotide bases Glucose Nucleotide bases Sugar-phosphate backbone 3 end 5 end Base pair (joined by hydrogen bonding) Old strands Nucleotide about to be added to a The DNA double helix new strand 5 end New strands 3 end 5 end 3 end 5 end
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3 Large molecules could have polymerized on hot rocks or clay originating polypeptides and short nucleic acids Where did the first polymers originate?
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This note was uploaded on 09/29/2011 for the course BIO 121 taught by Professor Pazymino during the Fall '08 term at UMass Dartmouth.

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lecture 9_tourofcell - Cells: The Working Units of Life How...

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