Oxidation of Organic Fuel Molecules During Cellular Respiration • During cellular respiration, the fuel (such as glucose) is oxidized, and O2 is reduced:Stepwise Energy Harvest via NAD+ and the Electron Transport Chain • In cellular respiration, glucose and other organic molecules are broken down in a series of steps • Electrons from organic compounds are usually first transferred to nicotinamide adenine nucleotide (NAD+), a coenzyme  As an electron acceptor, NAD+ functions as an oxidizing agent during cellular respiration  Each NADH (the reduced form of NAD+) represents stored energy that is tapped to synthesize ATPNAD+ and the Electron Transport Chain • NADH passes the electrons to the electron transport chain  Unlike an uncontrolled reaction, the electron transport chain passes electrons in a series of steps instead of one explosive reaction • O2 pulls electrons down the chain in an energy-yielding tumble  The energy yielded is used to regenerate ATPThe Stages of Cellular Respiration • Potential energy in glucose is contained in the reduced hydrocarbon bonds.  To use this energy, glucose must be oxidized to CO2 and water. • This involves Six major steps: 1. The transport of glucose into the cell using glucose transporters. 2. Glycolysis splits glucose into two pyruvate molecules. 3. Pyruvate oxidation produces acetyl CoA, which is then metabolized further. 4. The citric acid (or Krebs) cycle oxidizes acetyl coA to produce ATP and reduced electron carriers NADH and FADH2. • FADH2: flavin adenine nucelotide – derived from a B vitamin. 5. The electron transfer chain uses NADH/FADH2 from the citric acid cycle and glycolysis to maintain a proton gradient across the inner mitochondrial membrane. 6. This gradient drives an enzyme, ATP synthase, to produce ATP via Oxidative phosphorylation.Cellular Respiration 1. The transport of glucose into the cell using glucose transporters. 2. Glycolysis splits glucose into two pyruvate molecules. 3. Pyruvate oxidation produces acetyl CoA, which is then metabolized further. 4. The citric acid (or Krebs) cycle oxidizes acetyl CoA to produce ATP and reduced electron carriers NADH and FADH2. 5. The electron transfer chain uses NADH/FADH2 from the citric acid cycle and glycolysis to maintain a proton gradient across the inner mitochondrial membrane. 6. This gradient drives an enzyme, ATP synthase, to produce ATP via Oxidative phosphorylation.Cellular Respiration 1. The transport of glucose into the cell using glucose transporters. 2. Glycolysis splits glucose into two pyruvate molecules. 3. Pyruvate oxidation produces acetyl CoA, which is then metabolized further. 4. The citric acid (or Krebs) cycle oxidizes acetyl CoA to produce ATP and reduced electron carriers NADH and FADH2. 5. The electron transfer chain uses NADH/FADH2 from the citric acid cycle and glycolysis to maintain a proton gradient across the inner mitochondrial membrane. 6. This gradient drives an enzyme, ATP synthase, to produce ATP via Oxidative phosphorylation.Cellular Respiration 1. The transport of glucose into the cell using glucose transporters. 2. Glycolysis splits glucose into two pyruvate molecules. 3. Pyruvate oxidation produces acetyl CoA, which is then metabolized further. 4. The citric acid (or Krebs) cycle oxidizes acetyl CoA to produce ATP and reduced electron carriers NADH and FADH2. 5. The electron transfer chain uses NADH/FADH2 from the citric acid cycle and glycolysis to maintain a proton gradient across the inner mitochondrial membrane. 6. This gradient drives an enzyme, ATP synthase, to produce ATP via Oxidative phosphorylation.Oxidative phosphorylation • Oxidative phosphorylation accounts for almost 90% of the ATP generated by cellular respiration • A smaller amount of ATP is formed in glycolysis and the citric acid cycle by substrate-level phosphorylationCellular Respiration 1. The transport of glucose into the cell using glucose transporters. 2. Glycolysis splits glucose into two pyruvate molecules. 3. Pyruvate oxidation produces acetyl CoA, which is then metabolized further. 4. The citric acid (or Krebs) cycle oxidizes acetyl CoA to produce ATP and reduced electron carriers NADH and FADH2. 5. The electron transfer chain uses NADH/FADH2 from the citric acid cycle and glycolysis to maintain a proton gradient across the inner mitochondrial membrane. 6. This gradient drives an enzyme, ATP synthase, to produce ATP via Oxidative phosphorylation.Cellular Respiration 1. The transport of glucose into the cell using glucose transporters. 2. Glycolysis splits glucose into two pyruvate molecules. 3. Pyruvate oxidation produces acetyl CoA, which is then metabolized further. 4. The citric acid (or Krebs) cycle oxidizes acetyl CoA to produce ATP and reduced electron carriers NADH and FADH2. 5. The electron transfer chain uses NADH/FADH2 from the citric acid cycle and glycolysis to maintain a proton gradient across the inner mitochondrial membrane. 6. This gradient drives an enzyme, ATP synthase, to produce ATP via Oxidative phosphorylation.Glycolysis harvests chemical energy by oxidizing glucose to pyruvate • Glycolysis (“splitting of sugar”) is a metabolic pathway made up of a series of cytosolic enzymes that metabolize glucose. • Breaks down glucose into two molecules of pyruvate  A 6 carbon compound - into 2 x 3 carbon compounds. • Glycolysis occurs in the cytoplasm and has two major phases:  Energy investment phase  Energy payoff phaseSteps in glycolysis • Energy investment phase  Kinases use ATP to phosphorylate glucose and some of the intermediate molecules so that more ATP and NADH2 can ultimately produced. • NADH 0 • FADH2 0 • ATP -1Steps in glycolysis • NADH 0 • FADH2 0 • ATP -1Steps in glycolysis • NADH 0 • FADH2 0 • ATP -2Steps in glycolysis • NADH 0 • FADH2 0 • ATP -2Steps in glycolysis • NADH +2 • FADH2 0 • ATP -2 NAD+ is reduced to NADHSteps in glycolysis • NADH +2 • FADH2 0 • ATP 0 PGK removes a phosphate to convert ADP to ATPSteps in glycolysis • NADH +2 • FADH2 0 • ATP 0Steps in glycolysis • NADH +2 • FADH2 0 • ATP 0Steps in glycolysis • NADH 2 • FADH2 0 • ATP 2GlycolysisCellular Respiration 1. The transport of glucose into the cell using glucose transporters. 2. Glycolysis splits glucose into two pyruvate molecules. 3. Pyruvate oxidation produces