Lesson 7 (1).pdf

ENERGY GENERATION IN THE BODY Lesson 7 Energy generation in the body • Concept and functional role of biological oxidation. • Respiratory chain and ATP synthesis. • Role of the CAC in the generation of energy ELECTRON TRANSPORT CHAIN Electron-transfer chain: sequence of electron-carrying prot...

ENERGY GENERATION IN THE BODY Lesson 7 Energy generation in the body • Concept and functional role of biological oxidation. • Respiratory chain and ATP synthesis. • Role of the CAC in the generation of energy ELECTRON TRANSPORT CHAIN Electron-transfer chain: sequence of electron-carrying proteins that transfer electrons from substrates (NADH and FADH2) to molecular oxygen in aerobic cells. AH2 OXIDATION REACTIONS. CATABOLISM NAD+ or FAD NADH + H+ or FADH2 1 ELECTRON TRANSPORT CHAIN A Functions: ½ O2 + 2H+ H2O 2 ENERGY • Regenerate the oxidized forms of the coenzymes to continue the oxidation reaction (catabolism) • Enery release through the electron transport ELECTRON TRANSPORT CHAIN • Location  Inner mitochondrial membrane • Components: 4 complexes  I, II III and IV 2 carriers  Coenzyme Q and cytochrome C • Complex I, III and IV pump protons to the intermembrane space at the same time as the electrons pass through them. • Complexes are located on increasing affinity to electrons • The electrons are transported from NADH and FADH2 (electron donors) to oxygen (electron acceptor). ELECTRON TRANSPORT CHAIN Electron affinity Respiratory complexes: I, II, III, IV Electron donors: NADH and FADH2 Electron acceptor: Oxygen Free transporters: Coenzyme Q, cytochrome C ELECTRON TRANSPORT CHAIN AND OXIDATIVE PHOSPHORYLATION Oxidative phosphorylation: The enzymatic (by ATP synthase) phosphorylation of ADP to ATP coupled to electron transfer from a substrate to molecular oxygen. • Both processes are coupled  ATP synthase is also called Complex V. ENERGY RESPIRATORY CHAIN ADP + Pi ATP ATP SYNTHASE (endergonic process) ELECTRON TRANSPORT CHAIN AND OXIDATIVE PHOSPHORYLATION CHEMIOSMOTIC THEORY (MITCHELL) • Theory that explains how the electron transport chain and oxidative phosphorylation are coupled • Transmembrane differences in proton concentration are the reservoir for oxidative phosphorylation • 2 steps are involved: Proton pump  Re-entry of the protons through ATP synthase Chemiosmotic theory: The theory that energy derived from electron transfer reactions is temporarily stored as a transmembrane difference in charge and pH, which subsequently drives the formation of ATP in oxidative phosphorylation CHEMIOSMOTIC THEORY (MITCHELL) PROTON PUMP • Electron flow is accompanied by proton transfer across the inner membrane • The inner mitochondrial membrane is impermeable to protons • Proton-motive force  electrochemical energy inherent in the difference in proton concentration and the separation of charge across the inner mitochondrial membrane Proton -motive force Chemical potential (different pH) Electrical potential (different charge) CHEMIOSMOTIC THEORY (MITCHELL) RE-ENTRY OF THE PROTONS THROUGH ATP SYNTHASE • Protons flow passively back into the matrix through a proton pore in ATP synthase • Thermodynamically favorable process exergonic • Released energy is used for ATP synthase for the synthesis of ATP. • 4 protons are required to synthesize 1 ATP Proton -motive force Chemical potential (different pH) Electrical potential (different charge) ATP synthesis driven by protonmotive force THE CITRIC ACID CYCLE • Multistep catalytic process that converts acetyl-CoA derived from carbohydrates, fatty acids and amino acids to CO2, and produces NADH, FADH2, and ATP • Also called the tricarboxylic acid (TCA) cycle or the Krebs cycle GENERAL FEATURES: • Location Mitochondrial matrix • Functions:  Completely oxidizes Acetyl CoA to CO2. Produces NADH and FADH2 that are oxidized by the mitochondrial ETC to generate energy to form ATP.  Anabolic function: CAC is a source of biosynthetic intermediates. They can be used in the synthesis of glucose, fatty acids and amino acids.  THE CITRIC ACID CYCLE THE CITRIC ACID CYCLE • Each round consists of a series of 8 reactions that oxidize the acetyl group of acetyl-CoA to 2 CO2, 3NADH, 1FADH2 and 1 ATP • Regulation: Activators • ADP • NAD+ Inhibitors • Citrate • ATP, NADH THE CITRIC ACID CYCLE ENERGY BALANCE 4 protons are required to synthesize 1 ATP Each NADH generates 3 ATPs Each FADH2 generates 2 ATPs For each Acetyl CoA 3 NADH  9 ATPs 1 FADH2  2 ATPs 1 ATP 12 ATPs THE CITRIC ACID CYCLE • The citric acid cycle is an amphibolic pathway • Intermediates can be used in the following anabolic pathways: Glucose biosynthesis Fatty acids biosynthesis Amino acids biosynthesis Amphibolic pathway: A metabolic pathway used in both catabolism and anabolism.