Cellular Respiration & Metabolism, Exams of Law

Download Cellular Respiration & Metabolism and more Exams Law in PDF only on Docsity! Cellular Respiration Heyer 1 Metabolic Pathways: a summary Cellular Respiration & Metabolism Metabolism Bioenergetics • Flow of energy in living systems obeys: • 1st law of thermodynamics: – Energy can be transformed, but it cannot be created or destroyed. • 2nd law of thermodynamics: – Energy transformations increase entropy (degree of disorganization of a system). – Only free energy (energy in organized state) can be used to do work. • Systems tend to go from states of higher free energy to states of lower free energy. Coupled Reactions: Bioenergetics • Energy transfer from one molecule to another couples chemical reactions • Exergonic reaction: reaction releases energy • Endergonic reaction: reaction requires energy • Coupled bioenergetic reactions: the energy released by the exergonic reaction is used to power the endergonic reaction. Coupled Pathways: Bioenergetics • Energy transfer from one metabolic pathway to another by means of ATP. • Catabolic pathway (catabolism): breaking down of macromolecules. Releases energy which may be used to produce ATP. • Anabolic pathway (anabolism): building up of macromolecules. Requires energy from ATP. • Metabolism: the balance of catabolism and anabolism in the body. Cellular Respiration: ATP is the cell’s rechargable battery • Breaking down complex glucose molecule releases energy. • That energy is used to convert ADP into ATP. ADP + P + energy —› ATP • Energy is released as ATP breaks down into ADP and AMP. ATP —› energy + ADP + P Cellular Respiration Heyer 2 Forward reaction is exergonic Back reaction is endergonic • Cells use ATP by breaking phosphate bond and transferring energy to other compounds • Cells make ATP by transferring energy from other compounds to form phosphate bond Coupled Metabolic Pathways: via ATP Cellular Metabolism • Cellular Respiration provides ATP • Cellular “Work” requires ATP ATP drives endergonic reactions • The three types of cellular work are powered by the hydrolysis of ATP (c) Chemical work: ATP phosphorylates key reactants P Membrane protein Motor protein P i Protein moved (a) Mechanical work: ATP phosphorylates motor proteins ATP (b) Transport work: ATP phosphorylates transport proteins Solute P P i transportedSolute Glu Glu NH3 NH2 P i P i + + Reactants: Glutamic acid and ammonia Product (glutamine) made ADP + P Figure 8.11 Coupled reactions using ATP. Exergonic Oxidation of Organic Fuel • Controlled oxidation releases energy in small, usable increments • Redox reactions regulated through reducing and oxidizing agents Cellular Respiration Heyer 5 Glycolysis v “Light two matches” to get started vGlucose partially ozixidized. v Electrons harvested, ATP made. v Pyruvate is end product. Glycolysis summary Anaerobic Respiration Anaerobic Respiration = “fermentation” lactate fermentation Fermentation pathways regenerate NAD+ & dispose of pyruvate. Pyruvate Reduction alcohol fermentation Pyruvate Reduction Cellular Respiration Heyer 6 Glycolysis can lead to respiration or fermentation Aerobic Respiration OXIDIZED COENZYMES REDUCED COENZYMES REDUCED COENZYMES OXIDIZED COENZYMES Pyruvate transport & oxidation to acetate Pyruvate / H+ symporter mitochondrial matrix Pyruvate inter- membrane space cytosol H+ Proton gradient drives cotransport of pyruvate & H+ into matrix Aerobic Respiration Krebs Cycle •Acetate completely oxidized to CO2 •For each acetate through the cycle: • 3 (NAD+)Æ 3 (NADH+H+) • 1 FAD Æ 1 FADH2 • 1 ADP Æ 1ATP •(Remember, 1 glucose produced 2 acetates) Cellular Respiration Heyer 7 Krebs Cycle (Citric Acid Cycle) (Tricarboxylic Acid [TCA] Cycle) Carboxylic acid and keto acid intermediates Aerobic Respiration vHarvesting electrons from food: glycolysis & the Krebs cycle. vMaking a proton gradient: electron transport chain. vUsing the proton gradient to power ATP synthesis: chemiosmosis & oxidative phosphorylation. Respiration mechanisms Intermembrane space Matrix Outer membrane Inner membrane pumping protons proton gradient powers ATP synthesis H+ H+ H+ H+ H+H+ H+ H+H+ H+ H+ H+ H+ H+ H+ ADP + Pi ATPH+ H+ H+ H+ H+H+ H+ H+H+ H+ H+ H+ H+ H+ e- lower energy e-high energy H+ proton e- electron Oxidative phosphorylation: 2 parts Electron Transport Chain v Series of increasingly electronegative e- carriers in 3 membrane-bound complexes. vNADH starts at high energy level, FADH2 slightly lower. vO2 is the final e- acceptor.