BIOL 101 1st Edition Lecture 11 Outline of Last Lecture I Chemical Reactions II Exergonic Reactions III Endergonic Reactions IV Enzymes V Enzyme Substrate Complex VI Factors Affecting Enzyme Activity VII Control of Metabolism VIII ATP Outline of Current Lecture I Cellular Respiration II Redox Reactions III Overview of Respiration IV First Two Stages of Respiration Current Lecture I Cellular Respiration a The aerobic catabolism or organic nutrients b Requires O2 and carbon based food c Nutrients have potential energy stored in chemical bonds d Goal of cellular respiration is to convert the stable chemical energy in nutrients to a readily usable form ATP e Accomplish in a stepwise manner catabolic pathways i Chemical equation C6H12O6 O2 CO2 H2O ii G 686 kcal mole f Cell makes 36 ATPs glucose g h i j Each ATP requires 7 3 kcal mole of energy Yield of respiration is approximately 38 60 of energy is lost 40 is stored in ATP II Redox Reactions a Cells get energy from glucose during cellular respiration using a series of oxidation reduction reactions Redox i Oxidation Loss of electrons ii Reduction gain of electrons b Two types of reactions are always coupled together c One molecule loses an electron becomes oxidized and the electron is gained by another molecule becomes reduced d The loss and gain of electrons can be easily thought of as loss and gain of whole H atoms e Easy to monitor oxidation as loss of H atoms and reduction as gain of H atoms III Overview of Respiration a Glucose is broken down to CO2 and oxidized stripped of electrons b Electrons usually H atoms are removed in a series of redox reactions catabolic pathways c Electrons from glucose are eventually transferred to O2 then reduced to H2O d Overall process is exergonic and releases energy in stepwise manner e Energy is then captured in the form of ATP IV First Two Stages of Respiration a Glycolysis i Catabolic pathways with 10 chemical reactions ii Occurs in all living cells unity in life iii Although the overall respiration pathway requires O2 this first stage does not require oxygen iv Occurs in cytoplasm v Overall pathway for glycolysis 1 Glucose 10 reactions 2 pyruvates 2 C6H12O6 C3H4O3 vi Glucose 6 carbon is split into 2 pyruvates 3 carbons vii Glucose is partially oxidized some electrons are removed viii Catalyzed by enzymes called dehydrogenases 1 Generally 2 H atoms are removed by dehydrogenases 2 Require co enzymes to work 3 Act as temporary carriers for the electrons that are removed during oxidation reactions 4 Two important coenzymes that work with dehydrogenases during respiration a Nicotinamide Adenine Dinucleotide NAD i Exists in 2 forms ii NAD NADH b Flavin Adenine Dinulceotide FAD i Exists in 2 forms ii FAD FADH 5 Enzymes are only active in their oxidized forms form available to accept electrons ix Glycolysis produces a net gain of 2 ATPs per glucose molecule that enters the pathway x These 2 ATPs arise by substrate level phosphorylation direct ransfer of a phosphate from an intermediate in substrate in the pathway to ADP making ATP xi Glycolysis also produces 2NADHs reduced coenzyme these will be important in the last stage of respiration in which ATP is generated by oxidative phosphorylation xii Overall 1 Reactant 1 glucose 2 Products 2 pyruvates 2 ATPS 2 NADH can be used later to make ATP b Transition to Mitochondria i Rest of respiration occurs in mitochondria ii Pyruvate from glycolysis enters the matrix of the mitochondria further oxidizing and breaking it down iii Pyruvate has 3 carbons one carbon is completely oxidized in mitochondria producing CO2 iv The remaining 2 carbon group acetyl group is carried into the mitochondria by a molecule called coenzyme A v The electrons removed from pyruvate are transferred to NAD NADH reduced coenzyme vi Overall process 1 Pyruvate CoA NAD NADH CO2 acetyl CoA 2 Cytoplasm Mitochondrial matrix vii Overall 1 Reactants 2 pyruvates 2 Products 2 acetyl CoA 2 CO2 2 NADH can be used later to make ATP