1. 27b Prokaryotic oxygen and Evolution

2. Oxygen ______________: use oxygen for cellular respiration ______________: use oxygen if present, fermentation if not ______________: poisoned by oxygen, anaerobic resp/fermentation

3. Evolution Glycolosis and ATP chemiosmosis common to all organisms, implies early origin. Glycolosis does not require oxygen; oxygen not present in early atmsophere Hypothesis:

4. Photosynthesis Energized pigment couples with membrane proteins in ATP synthesis. Modern Archaea called extreme halophiles have the pigment bacteria rhodopsin, absorbs light and uses energy to pump H+ out of the cell (H+ gradient drives ATP synthesis). Purple and green sulfur bacteria split ____ instead of _____, don’t produce oxygen. Cyanobacteria (2.5 to 3.4 billion years ago): used _______ instead of _____. – Made organic compounds from light – Oxygen is the byproduct – Oxygen first reacted with _____ to form _____________ (lakes show red banding) – Oxygen gas was then released from the ocean to the atmosphere – Many prokaryotic species went extinct because of ____________. – Many modified to aerobic respiration.