Aerobic Respiration Pyruvate Oxidation The Citric Acid Cycle.
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Transcript of Aerobic Respiration Pyruvate Oxidation The Citric Acid Cycle.
Aerobic Respiration
Pyruvate Oxidation
The Citric Acid Cycle
What happens to pyruvate?
• depends on whether oxygen is present (aerobic respiration) or not (anaerobic respiration)
Pyruvate Oxidation
• if oxygen is present, the pyruvate molecules are transported from the cytoplasm into the mitochondrial matrix
Pyruvate Oxidation
Pyruvate Oxidation
• 3 enzyme-catalyzed changes:
• decarboxylation forming CO2 as a by-product
• oxidation of the 2-carbon molecule, causing a reduction of NAD+ to NADH
• attachment of coenzyme A (a derivative of vitamin B5), forming acetyl-CoA
Pyruvate Oxidation
The Citric Acid Cycle
(Also known as the Krebs Cycle)
The Citric Acid Cycle
• 8 enzyme-catalyzed reactions• occurs in the mitochondrial matrix• aerobic process• cyclic process: oxaloacetate is the
reactant of the first reaction and product of the last reaction
First reaction
Citric Acid Cycle Pathway
Major Processes:Decarboxylation (Reactions 3 & 4)
• 2 different reactions involve the removal of carbon as CO2
Major Processes:Oxidation (Reactions 3, 4, 6, 8)
• H atoms (with their associated electrons) are transferred to a coenzyme (NAD+ or FAD)
Major Processes:Energy Production (Reaction 5)
• during one of the reactions, ATP is generated by substrate-level phosphorylation.
• it is coupled to a reaction which has a large amount of free energy release
Summary
• oxaloacetate is regenerated in the last step
• all 6 carbons from glucose have been oxidized to CO2
• all of the energy from glucose is in the form of ATP, NADH and FADH2
Krebs Cycle Overall Reaction
2 acetyl CoA + 6NAD+ + 2 FAD + 2ADP + 2 Pi
4 CO2 + 6 NADH + 6 H+ + 2 FADH2 + 2 ATP
Summary
Animations
• Simple reaction review: http://www.science.smith.edu/departments/Biology/Bio231/krebs.html
• Animation & Quiz: http://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter25/animation__how_the_krebs_cycle_works__quiz_1_.html
Preview of ETC…
• If you’re confused about the Electron Transport Chain, this animation might help:
• http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120071/bio11.swf::Electron%20Transport%20System%20and%20ATP%20Synthesis