Lecture 12Outline of Last Lecture I. Cellular RespirationII. Redox ReactionsIII. Overview of RespirationIV. First Two Stages of RespirationOutline of Current Lecture I. Krebs CycleII. Oxidative PhosphorylationIII. Summary of Cellular RespirationIV. FermentationCurrent LectureI. Krebs Cyclea. Catabolic pathway b. Occurs in matrix of mitochondria only in the presence of O2c. 2 carbon acetyl group is completely broken down and oxidized to give 2 CO2d. Electrons are transferred to NAD+ and FAD to produce reduced coenzymes, NADH and FADH2e. Overall process:i. Acetyl-CoA (2 carbon) + Oxaloacetate (4 carbon)  citric acid (6 carbons)II. Oxidative Phosphorylationa. Occurs on the inner mitochondrial membraneb. Uses electrons that were transferred to NADH and FADH2 in stages 2-3 (reduced coenzymes)c. Electrons carried by reduced coenzymes are dropped at the electron transport chain (ETC)i. Electron transport chain  series of electron carrier molecules located on inner mitochondrial membraned. Electrons from the reduced coenzymes (NADH and FADH2) are passed along the chain and eventually to O2 (final electron acceptor)i. O2    H2Oii. (oxidized)  (reduced)e. During, some electron transfers along the electron transport chain, protons (H+) are pumped from the matrix into the inner membrane space creating an H+ gradient (proton gradient)i. Proton gradient = potential energy = proton motive forcef. Protons can re-enter the matrix of the mitochondria (down their electrochemical gradient) using a special transport protein called ATP synthasei. ATP synthase  transport protein for protons, but also an enzyme that catalyzes reaction: 1. ATP + Phosphate  ATP BIOL 1st Editiong. As protons pass through the ATP synthase, energy of proton gradient is harnessed to drive the endergonic reactionh. Chemiosmosis  using energy of proton gradient to make ATPi. For every NADH that drops electrons at the electron transport chain, enough energy is captured to make 3 ATPSj. Every FADH2 can be used to make 2 ATPSi. FADH2  2ATPk. Most of the ATP in the cell is produced by chemiosmosisl. Other important aspect is that NAD+ and FAD (oxidized coenzymes) are regenerated when they drop off their electronsi. Now able to act as ACTIVE coenzymes to accept more electrons and continue respirationm. Overall:i. Reactants: NADH (reduced coenzyme), FADH2 (reduced coenzyme), O2ii. Products: NAD+ (oxidized coenzyme), FAD (oxidized coenzyme), H2O, ATPIII. Summary Table of Cellular RespirationProcess Where What Goes In ProductsGlycolysis Cytoplasm 1 Glucose 2 Pyruvates2 NADH2 ATPsTransition toMitochondriaCytoplasm mitochondria2 Pyruvates 2 Acetyl Groups2 CO22 NADHKrebs Cycle Matrix of mitochondria 2 Acetyl Groups 4 CO26 NADH2 FADH22 ATPsOxidativePhosphorylationInner mitochondrialmembraneNADHFADH2O2NAD+FADH2O32 ATPsIV. Fermentationa. Anaerobic catabolism of organic nutrientsb. Glycolysis + one or 2 more chemical reactions to regenerate NAD+ (oxidized form of coenzyme)c. Products:i. 2 ATPsii. 2 Pyruvatesiii. 2 NADHd. In the absence of O2  can’t run the electron transport chain (need O2 as the final electron acceptor)e. Electrons from NADH are transferred back to pyruvate to make one of two products:i. Lactic acidii. Ethanolf. No ATP is generated by transferring electrons to pyruvate, but it regenerates NAD+ so that glycolysis can continueg. Energy yield from fermentation = 2 ATP/glucoseh. Examples:i. Ethanol fermentation  yeast makes beerii. Muscle cells not enough O2  lactic acid fermentation makes sore