Transit and Metabolic Maps: Complex and Functional Glycolysis Coupled with Cellular Respiration Maximizes Energy Generation Carbon Oxidation is Coupled with Energy Rich Reduction Which molecule is more energy rich on a per carbon basis? Free- Energy Universal-Currency: ATP ATP hydrolysis is exergonic ATP + H 2 O ADP + P i G = - 30 kJ/mol ATP hydrolysis drives metabolism in heterotrophs Light energy is trapped as ATP in phototrophs Why is ATP an excellent energy currency? ATP: High Phosphoryl-Transfer Potential ATP and hydrolysis products differences: Electrostatic repulsion Resonance stabilization Hydration stabilization How can an energetically unfavorable reaction be made spontaneous? Substrate-Level ATP Phosphoryation Requires High Phosphoryl-Transfer Potential Standard Free Energy of Hydrolysis Duration of Alternative Energy Sources Anaerobic Systems Aerobic Systems ATP: tennis serve Oxidative phosphorylation: Creatine phosphate: sprint race > 500 m Glycolysis: 200 m dash ATP: A Multifunctional Metabolite High turnover (ca. 90 lbs/24 hrs) Additional Activated Carriers Nicotinamide Adenine Dinucleotide (NAD + ) Electron carriers in oxidation-reduction reactions NADH functions in catabolism NADPH functions in anabolism Nicotinamide Adenine Dinucleotide Phosphate (NADP + ) Additional Activated Carriers Flavin adenine dinucleotide (FAD) Electron carriers in oxidation-reduction reactions FADH functions in both catabolism and anabolism Substrate Specificity for Dinucleotide Oxidation-Reduction Reactions What is the reducing agent for this reaction? Fatty Acid Biosynthesis via Keto Reduction to a Methylene Unit Coenzyme A: an Activated Carrier of Two Carbon Fragments Coenzyme A structure Acetyl CoA + H 2 O Acetate + CoA + H + G = -31 kJ/mol Activated Carries Utilized in Metabolism Coenzymes Derived from Vitamins What coenzymes are derived from these vitamins? Metabolic Regulation Substrate accessibility (compartmentalization) Enzyme amount (transcriptional and translation control) Catalytic activity (allosteric control, covalent modifications, hormone signaling, and cell energy status) Energy charge = [ATP] + [ADP]/([ATP] + [ADP] + [AMP]) Energy Utilization Linked with Building and Degrading Metabolites What macromolecules are stored and/or metabolized by humans for energy? Metabolic Fuel Generation by Digestion Match the enzyme with the reaction: - Protease - Amylase - Lipase Lipid Transport via Lipoproteins (aka Chylomicrons) to Adipocytes Lipoproteins - esterified cholesterol, proteins and triacylglycerols combined Adipose cells A Liver Cell Fat globule Mitochondria Glycogen granules Glycogen molecule with sugar units What advantages are there in having glycogen be a branched polymer? Human Sugar Storage in Liver and Muscle Tissue Glycogen Degradation by Glycogen Phosphorylase (Phosphorolysiss) Trapped in the cell Protein Degradation by Ubiquitin Tagging and Proteasome Digestion Cutaway view showing inner chamber Protease active sites Proteasome Protein Degradation Protein turnover important in: Cell signaling Maintaining high protein quality Does this phosphoarginine metabolite rich in the muscles of certain invertebrates have a high phosphoryl-transfer potential? What function might this metabolite have? Test Your Knowledge G of ATP Hydrolysis with Varying [Mg 2+ ] How does decreasing [Mg +2 ] affect G of ATP hydrolysis? Can this trend be justified? Problems: 26, 27 and 41