EXSC%223:%Week%of%11/14%!Textbook%notes%Ch.%24.3%%24.3!Metabolism!is!the!sum!of!all!biochemical!reactions!in!the!body!• Metabolic!processes!are!either!anabolic!or!catabolic!o Anabolic=synthetic,!building!up!o Catabolic=degradative,!tearing!down!• Cellular!respiration!o Catabolic!reactions!o Food!fuels!(mostly!glucose)!are!broken!down!in!cells!o Energy!released!is!captured!as!ATP!§ Cells’!energy!currency!• 3!major!stages!of!processing!energy-containing!nutrients!1. in!GI!tract!a. digestion!b. absorbed!nutrients!carried!to!tissues!2. in!tissues…either!anabolic!or!catabolic!pathways!a. anabolic:!nutrients!built!into!lipids,!proteins,!and!glycogen!b. catabolic:!broken!down!to!pyruvates!and!acetyl!CoA!3. in!mitochondria!a. catabolic!b. requires!oxygen!c. completes!breakdown!of!foods!d. produces!CO2!and!H2O!and!ATP!• Oxidation-Reduction!Reactions!(Redox)!o Oxidation!§ Oxygen!is!gained!§ Loss!of!hydrogen!§ Loss!of!electrons!o Redox!§ Oxidized!substance!loses!energy!§ Reduced!substance!gains!energy!o Catalyzed!by!enzymes!§ Helped!by!coenzymes!§ Enzymes!can!catalyze!removal!of!hydrogen!atoms,!but!they!can’t!hold!onto!it!§ So!coenzymes!act!as!hydrogen!acceptors!§ NAD+!§ FAD!Lecture%11/14%notes!What!do!we!mean!when!we!talk!about!metabolism?!• Metabolism:!biochemical!reactions!inside!cells!involving!nutrients!• Two!types!of!reactions!o Anabolism:!synthesis!of!large!molecules!from!small!ones!§ Ex/!amino!acids!into!proteins!§ Ex/!glucose!into!glycogen!o Catabolism:!hydrolysis!of!complex!structures!to!simple!ones!§ HINT:!thing!CATAstrophe=disaster=break!down!§ Ex/!proteins!into!amino!acids!§ Ex/!glucose!into!CO2!and!H2O!• Cellular!respiration!o Also!called!oxidative!metabolism!and!oxidative!phosphorylation!o Breakdown!of!food!(catabolism)!to!form!ATP!in!cells!(anabolism)!§ C6H12O6!+!O2!à!CO2!+!H2O!and!ADP!+!Pi!à!ATP!+!heat!!!!!!(catabolic)! ! ! (anabolic)!o Use!ATP!to!drive!reactions!(cross-bridge!cycling)!or!to!regulate!enzymes!(phosphorylation)!§ Phosphorylated!molecules!activate!to!perform!other!functions!3!stages!of!metabolism!1. Digest!in!GI!tract!a. Absorb!b. Transport!via!blood!to!tissue!cells!2. Anabolism!and!catabolism!of!nutrients!3. Oxidative!breakdown!in!mitochondria!forming!water!a. Some!energy!released!is!used!to!form!ATP!Oxidation-Reduction!(Redox)!Reactions!• Oxidation=!gain!oxygen!or!loss!of!H!atoms!o Anytime!you!lose!H,!you!lose!electrons!• Redox!reactions!o Oxidized!substances:!lose!electrons!and!energy!o Reduced!substances:!gain!electrons!and!energy!o Catalyzed!by!enzymes!o Wherever!electrons!go,!you!have!more!energy!• Enzymes!for!redox!o Dehydrogenases:!removal!of!hydrogen!atoms!o Oxidases:!transfer!of!oxygen!o Require!help!§ Coenzymes!act!as!H!(or!electron)!acceptors!• Nicotinamide!adenine!dinucleotide!(NAD+)!• Flavin!adenine!dinucleotide!(FAD)!ATP!synthesis!• 2!mechanisms!1. substrate!level!phosphorylation!a. high!energy!phosphate!groups!are!directly!transferred!from!phosphorylated!substrates!to!ADP!b. phosphate!removed!from!one!molecule!to!another!by!an!enzyme!to!make!ATP!c. necessary!enzymes!are!in!cytosol!for!glycolysis!and!in!mitochondria!for!the!krebs!cycle!2. oxidative!phosphorylation!a. only!happens!in!mitochondria!b. more!complex!process!c. produces!more!ATP!d. most!ATP!is!produced!by!this!process!e. chemiosmotic!process!i. potential!energy!(H+!gradient)!!transferred!to!chemical!energy!(ATP)!f. H+!pumps!create!a!gradient!(potential!energy):!moves!H+!ions!out!of!the!matrix!and!into!the!space!between!the!inner!and!outer!membranes!of!the!mitochondrion!g. ATP!synthase!(similar!to!a!pore!in!the!membrane)!allows!H+!to!move!along!its!concentration!gradient!back!into!the!matrix!h. Each!H+!causes!the!protein!to!change!shape!i. As!the!H+!move!back!into!the!matrix,!ATP!is!produced!j. Red!blood!cells!don’t!have!mitochondria!i. Can’t!carry!out!oxidative!phosphorylation!ii. Transport!oxygen!but!can’t!use!it!to!make!ATP!Carbohydrate!metabolism!• Oxidation!of!glucose!o C6H12O6!+!6O2!à!6CO2!+!6H2O!and!ADP!+!Pi!à!34ATP!+!heat!o Anaerobic:!produces!4!ATP!per!molecule!of!glucose!§ faster!o Aerobic:!produces!34!ATP!per!molecule!o f !glucose!§ Slower!o Sometimes!the!body!has!preference!for!one!over!the!other!o It!does!not!have!to!do!with!the!amount!of!oxygen!available!• Complete!glucose!catabolism!requires!3!pathways!o Glycolysis!o Krebs!cycle!o Electron!transport!chain!(ETC)!!Textbook%notes%Ch.%24.4%24.4!Carbohydrate!metabolism!is!the!central!player!in!ATP!production!• All!food!carbohydrates!consumed!are!converted!to!glucose!to!be!metabolized!• Glucose!enters!tissue!cells!by!facilitated!diffusion!• Glucose!is!phosphorylated!immediately!after!it!enters!the!cell!o Phosphate!group!is!added!to!its!6th!carbon!o Glucose!+!ATP!à!glucose-6-PO4!+!ADP!o Traps!glucose!in!the!cell!o This!reaction!can!only!be!reversed!by!intestinal!epithelial!cells,!kidney!tubule!cells,!and!liver!cells!• Catabolic!AND!anabolic!pathways!for!carbohydrates!begin!wit!glucose-6-phosphate!• Oxidation!of!glucose!o Catabolism!(breakdown)!of!glucose!has!3!pathways!§ Glycolysis!§ Krebs!(citric!acid)!cycle!§ Electron!transport!chain!(ETC)!and!oxidative!phosphorylation!o Glycolysis!§ Anaerobic!process:!does!not!use!oxygen!§ Occurs!in!cytosol!§ Converts!glucose!to!2!pyruvate!molecules!1. Glucose!is!phosphorylated!and!converted!to!fructose-6-phosphate!a. Phosphorus!added!to!6th!carbon!b. Cost:!1!ATP!2. Fructose-6-phosphate!is!phosphorylated!to!fructose-1,6-biphosphate!a. Phosphorus!added!to!1st!carbon!b. Cost:!1!ATP!3. Fructose-1,6-biphosphate!is!split!into!two!3-carbons!4. The!two!3-carbon!molecules!are!oxidized!by!the!removal!of!H+!which!is!picked!up!by!NAD+!(now!NADH)!5. Phosphate!groups!are!attached!to!each!oxidized!fragment!6. Phosphates!are!cleaved!off!and!combined!with!ADP!a. Forms!4!ATP!b. Called!substrate-level!phosphorylation!c. Left!with!2!pyruvates!7. Final!products!a. 2!pyruvates!b. 2!NADH!c. 4!ATP!(NET!ATP!gain!is!2!because!2!ATP!were!spent)!o what!happens!to!the!pyruvates!next…!§ if!molecular!oxygen!is!available:!they!move!into!the!mitochondria!to!enter!the!Krebs!cycle!• there!is!limited!NAD+!so!glycolysis!can!only!continue!if!the!NADH!is!relieved!of!the!H!it!is!carrying!• presence!of!oxygen!allows!the!NADH!to!relieve!the!H!to!it!to!produce!water!•