Respiration Transforms Energy Anaerobically (without O2): 4 ATP Aerobically: 38 ATP

Glycolysis transforms nrg, but not efficiently Transforms energy – but low efficiency 2 ATP • 686 kcal/glucose nets 2 ATP • 7.3kcal/ATP e- e- NADH = < 4% of glucose’s energy

Pyruvate options Anaerobic options All Organisms plants & animals yeast bacteria muscle cells

The Mitochondria - Site of Aerobic Respiration • Glycolysis here all organisms • Aerobic Resp Citric Acid Cycle (Krebs) here Electron Transport across here

Aerobic Respiration Overview

Readying Pyruvate for The Krebs Cycle Each 3 C Pyruvate is modified into a 2 C Acetyl CoA The 2 C are used to make 2 CO2 e- Again, e- are carried via NADH two glucose C

The Krebs (aka Citric Acid) Cycle …each 3 C pyruvate into acetyl CoA + oxaloacetate = 6 C molecule Each step produces a modified product via enzyme action two more glucose C to CO2 per turn More e- stripped off for the e- transport chain In summary, three major events occur during the Krebs cycle. One GTP (guanosine triphosphate) is produced which eventually donates a phosphate group to ADP to form one ATP; three molecules of NAD are reduced; and one molecule of FAD is reduced. Although one molecule of GTP leads to the production of one ATP, the production of the reduced NAD and FAD are far more significant in the cell's energy-generating process. This is because NADH and FADH2 donate their electrons to an electron transport system that generates large amounts of energy by forming many molecules of ATP. ATP NADH FADH2 http://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter25/animation__how_the_krebs_cycle_works__quiz_1_.html

Subtotal: ATP ATP ATP ATP ATP ATP At this point: c c c c c c c c c e-

Final Step – e- Transport Chain H from lose e-, build up across membrane protons (H+) pumped across the membrane producing a gradient e- transport chain through inner membrane proteins Chemiosmosis of ions down the gradient ATP Source of H? production of ATP http://www.youtube.com/watch?v=xbJ0nbzt5Kw http://www.youtube.com/watch?v=3y1dO4nNaKY&NR=1

Result – Mass Production of ATP (or thereabouts) In glycolysis of cellular respiration, NADH produces 2ATP because one ATP is used to transport a molecule of NADH into the mitochondria and continue with aerobic respiration. However, in pyruvate decarboxylation and the Krebs cycle, each NADH yields 3ATPs. FADH2 yields 2 ATPs. It is tempting to try to view the synthesis of ATP as a simple matter of stoichiometry (the fixed ratios of reactants to products in a chemical reaction). But (with 3 exceptions) it is not. Most of the ATP is generated by the proton gradient that develops across the inner mitochondrial membrane. The number of protons pumped out as electrons drop from NADH through the respiratory chain to oxygen is theoretically large enough to generate, as they return through ATP synthase, 3 ATPs per electron pair (but only 2 ATPs for each pair donated by FADH2). With 12 pairs of electrons removed from each glucose molecule, * 10 by NAD+ (so 10x3=30); and * 2 by FADH2 (so 2x2=4), this could generate 34 ATPs. Add to this the 4 ATPs that are generated by the 3 exceptions and one arrives at 38. But * The energy stored in the proton gradient is also used for the active transport of several molecules and ions through the inner mitochondrial membrane into the matrix. * NADH is also used as reducing agent for many cellular reactions. So the actual yield of ATP as mitochondria respire varies with conditions. It probably seldom exceeds 30.

Summary – Know at least this much! oxidized Each step generates e- transport molecules Extra C become waste (exhaled) e- used to create a concentration gradient Chemiosmosis yields most ATP reduced