Biology 45 - MetabolismAnna Miller, MS, RD 1Biology 45Metabolism• The sum total of all chemical reactions that go on in living cells• Energy Metabolism  The reactions by which the body obtains and spends the energy from food Begins with the end products of digestion. What are they? They are broken down to H2O and CO2 with the formation of ATPBiology 45Coupled Reactions• Anabolic and Catabolic reactions Know these terms! Review from AP• Energy generated from catabolic reaction enables anabolic reaction to take placeBiology 45ATP•Adenosine TriPhosphate The body’s energy currency The form of fuel that cells directly use•Chemical energy•What are other forms of energy?Biology 45 - MetabolismAnna Miller, MS, RD 2Biology 45Biology 45Adenosine TriphosphateBiology 45ATP & ADPBiology 45 - MetabolismAnna Miller, MS, RD 3Biology 45Chemical Reactions• Enzymes Cofactors•Coenzymes NAD (niacin – a B vitamin) FAD (riboflavin – a B vitamin) Coenzyme A (CoA) (panthothenic acid –a B vitamin)Biology 45Glucose Metabolism - Part 1• Glycolysis Splits glucose into 2 pyruvates Transfers electrons to NAD Produces some ATP (net, 2) Occurs in the cytosol of the cell Reversible (pyruvate → glucose) No oxygen is required: anaerobic pathwayBiology 45Biology 45 - MetabolismAnna Miller, MS, RD 4Biology 45• Pyruvate is converted to Acetyl CoA  Aerobic reaction In the mitochondria Releases CO2 Electrons are transferred to NAD Irreversible - IMPORTANT POINT!Glucose Metabolism - Part 2Biology 45Pyruvate-to-Acetyl CoABiology 45Glucose Metabolism - Part 3• The Kreb Cycle AKA The Tricarboxylic Acid Cycle or The Citric Acid Cycle Acetyl CoA enters (2 carbons) Combines with Oxaloacetate 2 carbons are released as CO2 Electrons are transferred to NAD and FAD Aerobic pathwayBiology 45 - MetabolismAnna Miller, MS, RD 5Biology 45The TCA CycleBiology 45Glucose Metabolism - Part 4• The Electron Transport Chain (ETC) In the inner walls of the mitochondria The final pathway in energy metabolism Accepts electrons from NAD and FAD Energy from these are transferred to make ATP Produces large amounts of ATP Produces water Oxygen is neededBiology 45The Results!• All of the carbons, hydrogens and oxygens of glucose end up as CO2and H2O• The energy that was in the chemical bonds of glucose ends up in ATP But we don’t work at 100% efficiency!Biology 45 - MetabolismAnna Miller, MS, RD 6Biology 45Sometimes…… • Pyruvate is converted to Lactic Acid Anaerobic Pathway When muscles don’t have enough oxygen for aerobic pathway: during high intensity exercise Lactic acid fatigues musclesBiology 45Biology 45Glucose Metabolism• Glycolytic System for producing ATP Glycolysis Lactic Acid pathway• Aerobic or Oxidative System for producing ATP Pyruvate to Acetyl Co, Kreb Cycle, ETCBiology 45 - MetabolismAnna Miller, MS, RD 7Biology 45What about Fat and Protein?• The end products of Fat and Protein digestion feed into the same pathways that metabolize glucose, in various, specific pointsBiology 45Glycerol & Fatty AcidsBiology 45Triglycerides• Lipolysis (breakdown/hydrolysis) of TG yields: Glycerol • Glycolysis Fatty Acids• The TCA cycle • Carnitine shuttles fatty acids into the mitochondria Fat burner?Biology 45 - MetabolismAnna Miller, MS, RD 8Biology 45Fatty acids-to-acetyl CoA, cont’dBiology 45Biology 45Important!• Fatty acids cannot be converted to glucose. Why not? • Because…… Fatty acids enter at the point of acetyl CoA 1-way arrow from pyruvate to acetyl CoA (irreversible rx)• Fatty acids cannot be converted to glucose—Ever!!Biology 45 - MetabolismAnna Miller, MS, RD 9Biology 45To metabolize fatty acids, you have to burn some glucoseBiology 45Amino AcidsBiology 45An Overview(simple)Biology 45 - MetabolismAnna Miller, MS, RD 10Biology 45An Overview(not as simple!)Biology 45FeastingBiology 45FastingBiology 45 - MetabolismAnna Miller, MS, RD 11Biology 45Why Ketones are Produced• Where will you get glucose if you’re fasting or eating almost no CHO? From Protein ……thanks to gluconeogenesis• Gluconeogenesis involves Oxaloacetate being converted to glucose (carbon skeletons of some AAs are converted to oxaloacetate) Oxaloacetate is siphoned off, diverted away from the Kreb Cycle. What happens to acetyl CoA?• Acetyl CoAs build up• They condense to form KetonesBiology 45Biology 45Ketosis• Formation of Ketones: Ketonemia Ketonuria• Ketoacidosis• This happens whenever cells are deprived of glucose Fasting Low CHO diet Untreated diabetes • Ketosis produces a loss of