Download
1 / 26
270 likes | 440 Vues
Origin of Life. Abiogenesis. Chemistry finds a biological vessel. Microspheres – Cell Membranes ?. Microspheres -Membranes. The First Duplicating Cell - Membrane PLUS RNA. Metabolism and DNA had to happen at the same time.
E N D
Origin of Life Abiogenesis
Chemistry finds a biological vessel Microspheres – Cell Membranes ?
Metabolism and DNA had to happen at the same time http://bytesizebio.net/index.php/2009/10/11/weekly-poll-replicators-first-vs-metabolism-first/ http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37141998000400001
Or is it Metabolism first ? Metabolism before Nucleic - Some scientists believe that the steps to create a self-replication molecule, as posited by the “RNA world” hypothesis would be too complex and impossible to sustain. They also argue that before such an orderly process as self-replication would arise, it would be more likely that chemical reactions involving the abundant inorganic compounds present on primitive Earth would have predominated. At the end of the 1980s, GüntherWächtershäuser, a German biochemist, proposed the “metabolism first” hypothesis. He observed that iron pyrite (also known as iron disulfide), or fool’s gold, is able to catalyze biochemical reactions and the presence of iron pyrite on the early Earth would have quickly led to a proliferation of chemical reactions that take place in living things today. Indeed, many enzymes present in modern cells contain iron pyrite clusters within their structure, attesting to the importance of fool’s gold. The “metabolism first” hypothesis essentially posits that the precursor to life was not a nucleic acid-based chain that replicated itself, but a structure that metabolized inorganic compounds on the surface of iron pyrite, most likely around small deep-sea hydrothermal vents.
Summary A protobiont is an aggregate ofabiotically produced organic molecules surrounded by a membrane or a membrane-like structure. Protobionts exhibit some of the properties associated with life, including simple reproduction, metabolism and excitability, as well as the maintenance of an internal chemical environment different from that of their surroundings. It has been suggested that they are a key step in the origin of life on earth. Experiments by Sidney W. Fox and Aleksandr Oparin have demonstrated that they may be formed spontaneously, in conditions similar to the environment thought to exist on an early Earth. These experiments formed liposomes and microspheres, which have membrane structure similar to the phospholipid bilayer found in cells.Nanobes or nanobacteria, being too small to be functional living organisms, may be an example of naturally occurring protobionts
Molecules that build Amino acids and Proteins
Amino Acids : Building Blocks for Proteins • 20 Amino Acids • Known by first 3 letters • Several amino acids joined together form polypeptide chain • Building blocks for proteins • Each protein differs by sequenceof amino acids
Evolution on Earth Chemistry Builds the Tree of Life
Extinction Events Climate change, Impacts, Disaster species, Vulcanism
