Acetyl CoA

1. Acetyl CoA The Ubiquitous Energy Source Paul Hirn and Paul Schillio Chemistry for Biology Teachers Washington University in St. Louis

2. Read this box from top to bottom following the red arrow This sequence of steps represents catabolic processes Read this box from bottom to top following the green arrow This sequence of steps represents anabolic processes Guide to the Slides

3. Carbohydrate Catabolism Glycolysis: 1 glucose into two 3C molecules of pyruvate (occurs in cytoplasm) Pyruvate oxidized into CO2 and acetyl CoA Acetyl CoA enters the Kreb’s cycle (in mitochondria) Acetyl CoA is added to 4C oxyloacetate to form 6C citric acid Citric acid oxidized - energy (NADH, FADH2, ATP) is used to power Electron Transport Chain for ATP synthesis (ATP synthase) Glucose is an energy storage molecule Two 3C PGAL are assembled in cytoplasm to make glucose (C6H12O6) 3C PGAL is formed and released into the cytoplasm NADPH (from photosystems) adds energy to the cycle CO2 enters from the outside - attached to RuBP by Rubisco) Electron carriers enter the Calvin cycle H+ ions flow back out through the ATP synthase to make ATP H+ ions are pumped IN the membrane Split H2O into H+ and O2 (waste is released) Absorb light energy Occurs in photosystems Carbohydrate Anabolism Carbohydrates

4. Lipid Catabolism Occurs in liver Lipids break down to acetic acid, enter the mitochondria Fatty acid spiral removes 2C pieces (acetyl CoA) from fatty acid chain each turn Acetyl CoA enters the Kreb’s cycle (in mitochondria) Acetyl CoA is added to 4C oxyloacetate to form 6C citric acid Citric acid oxidized - energy (NADH, FADH2, ATP) is used to power Electron Transport Chain for ATP synthesis (ATP synthase) Fat oxidation is fast, but incomplete, leaving build-ups of ketones in the blood Lipids store energy Build the lipid chain longer and larger Reduction reaction (add H+) and use NADPH Use energy from ATP, join multiple units of acetyl CoA to form a fatty acid chain Begins with acetyl CoA plus 2C unit (malonyl CoA) Occurs in cytoplasm Lipid Anabolism Lipids

5. Protein Catabolism Proteins hydrolyzed into amino acids Amino acids oxidized by removing amine group (as NH3) By-product of this oxidation is fumarate (fumaric acid), an intermediate in Kreb’s cycle Addition of H2O turns it to malate Oxidation converts it to oxaloacetate Add it to acetyl CoA yields citric acid Citric acid oxidized - energy (NADH, FADH2, ATP) is used to power Electron Transport Chain for ATP synthesis (ATP synthase) Leftover ammonia is combined with CO2 (in the liver) to produce urea (urea cycle) Amino acids can be converted directly into pyruvate as an immediate energy source Acetyl CoA enters the Kreb’s cycle Acetyl CoA is added to 4C oxyloacetate to form 6C citric acid Citric acid oxidized - energy (NADH, FADH2, ATP) is used to power ETC for ATP synthesis (ATP synthase) Now we have the components (raw materials) to build any of the 12 AA’s the body can produce This will deaminate a different AA to create alpha Keto acid (the foundation of all amino acids) Fumarate converted to oxaloacetate will convert into aspartate (substrate of urea cycle) Synthesis of amino acids cannot be accomplished by reverse of the reaction that created acetyl CoA 8 essential AA’s can only be taken in through diet Human body can synthesize 12 amino acids enzymes join AA’s to each other to form the chains tRNA transfers the specific amino acid to the ribosome mRNA attaches to a ribosome Through protein synthesis (in the cytoplasm) the amino acids are arranged to form long chains Protein Anabolism Proteins