Cellular Respiration - Harvesting Chemical Energy PDF

28/09/2023 Cellular Respiration MITOCHONDRIA Harvesting Chemical Energy 1 2 Cellular respiratio...

28/09/2023 Cellular Respiration MITOCHONDRIA Harvesting Chemical Energy 1 2 Cellular respiration Mitochondria catabolic process 2 membrane uses O2 as a reactant for the breakdown of organic Outer – smooth molecules Inner – folded (CRISTAE) carbohydrates, fats, proteins Cristae overall process: greater surface area for Organic compounds + O2  CO2 + H2O + Energy enzymes that synthesize ATP traditional to start with glucose: encloses matrix Mitochondrial matrix C6H12O6 + 6O2  fluid-filled space 6CO2 + 6H2O + Energy (ATP + heat) DNA, ribosomes, Fermentation enzymes Another type of catabolic process Partial degradation of sugars in the absence of oxygen Urry et al. 2017. Essential Biology 11th Edition Urry et al. 2017. Essential Biology 11th Edition 3 4  28/09/2023 ATP The bonds between phosphate groups can be broken by hydrolysis ATP -> ADP + Pi releases 7.3 kcal of energy per mole of ATP 5 6 3 METABOLIC STAGES: GLYCOLYSIS, CITRIC ACID CYCLE & OXIDATIVE PHOSPHORYLATION Urry et al. 2017. Essential Biology 11th Edition 7 8  28/09/2023 ELECTRON TRANSPORT CHAIN electrons move from molecule to molecule until they combine with oxygen & hydrogen ions to form H20 As they are passed along the chain, the energy carried by these electrons is stored in the mitochondrion in a form that can be used to synthesize ATP via OXIDATIVE PHOSPHORYLATION Oxidative phosphorylation produces ~ 90% of the ATP Some ATP is generated in glycolysis & Krebs cycle by generated by respiration SUBSTRATE-LEVEL PHOSPHORYLATION Urry et al. 2017. Essential Biology 11th Edition 9 10 Urry et al. 2017. Essential Biology 11th Edition Glycolysis 1 GLUCOSE (6 carbon-sugar) - split into TWO 3- CARBON SUGARS These smaller sugars are oxidized & rearranged to form 2 molecules of PYRUVATE Each of the 10 steps in glycolysis - catalyzed by a specific enzyme 2 phases: ENERGY INVESTMENT PHASE & ENERGY PAYOFF PHASE 11 12  28/09/2023 Energy Investment Phase Energy Payoff Phase Urry et al. 2017. Essential Biology 11th Edition Urry et al. 2017. Essential Biology 11th Edition 13 14 Urry et al. 2017. Essential Biology 11th Edition Pyruvate oxidation to Acetyl CoA Glycolysis occurs with or without O2 G3P More than 3/4 of the original energy in glucose is still present in 2 molecules of pyruvate If O2 is present, pyruvate enters the mitochondrion for Krebs cycle 1 Glucose = 2 Pyruvate *Acetyl CoA + Oxaloacetate = Citrate Urry et al. 2017. Essential Biology 11th Edition 15 16  28/09/2023 KREBS CYCLE/ CITRIC ACID CYCLE conversion of pyruvate & Krebs cycle produces (8 steps) large quantities of electron carriers oxaloacetate - recycled acetate - broken down to CO2 (NADH, FADH2) Per cycle: 1 ATP by substrate-level phosphorylation, 3 NADH, & 1 FADH2 (another electron carrier) per acetyl CoA x 2 per glucose 17 18 Oxidative Phosphorylation: Thousands of copies of the ETC are found in the extensive surface of the cristae, the inner membrane of the Electron Transport Chain & Chemiosmosis mitochondrion 4 of 32 ATP produced by respiration of glucose are derived from substrate-level phosphorylation Majority of the ATP comes from the energy in the electrons carried by NADH (and FADH2) The energy in these electrons is used in the electron transport system to power ATP synthesis 19 20  28/09/2023 Electrons carried by NADH are transferred to the first Electrons from NADH or FADH2 ultimately pass to molecule in the ETC, oxygen (terminal e-acceptor) FLAVOPROTEIN (FMN) ETC generates no ATP directly electrons continue along the chain which includes several cytochrome proteins & one lipid carrier Function - break the large free energy drop from food to O2 into a series of smaller steps that release energy Electrons carried by FADH2 in manageable amounts have lower free energy & The movement of electrons along ETC contribute to are added to a later point chemiosmosis & ATP synthesis in the chain Urry et al. 2017. Essential Biology 11th Edition 21 22 ATP synthase Unlike the explosive release of heat energy that would cristae occur when H2 & O2 combine, cellular respiration uses an makes ATP from ADP & ETC to break the fall of electrons to O2 into several steps Pi ATP used the energy of an existing proton gradient to power ATP synthesis Chemiosmosis – process in which energy stored in the form of a H ion gradient across a membrane is used to drive cellular work such as ATP synthesis 23 24  28/09/2023 Proton-motive force Proton gradient - produced by movement of e- along ETC Several chain molecules can use the exergonic flow of e- to pump H+ from the matrix to the intermembrane space This concentration of H+ is the proton-motive force 25 26 Mitochondrion Chloroplast Liver, Heart cells Brain cells MITOCHONDRION CHLOROPLAST STRUCTURE STRUCTURE H+ Diffusion Intermembrane Thylakoid space space Electron Membrane transport chain Key ATP synthase Higher [H+] Matrix Stroma Lower [H+] ADP + P i ATP H+ 1 NADH = 2.5 ATP 1 FADH2 = 1.5 ATP 27 28  28/09/2023 SUMMARY Anaerobic Respiration & Fermentation Glycolysis 2 ATP 2 Enables some cells to produce ATP without Ok 2 NADH 3 or 5 Pyruvate to Acetyl CoA 2 NADH 5 Citric Acid Cycle 2 ATP 2 Glycolysis generates 2 ATP whether oxygen is present (aerobic) or not (anaerobic) 6 NADH 15 2 FADH2 3 Anaerobic respiration uses ETC but oxygen is not TOTAL 30 or 32 ATP the final electron acceptor Anaerobic catabolism of sugars can occur by In the summary equation of cellular respiration: fermentation C6H12O6 + 6O2  6CO2 + 6H2O 29 30 ALCOHOL FERMENTATION LACTIC ACID FERMENTATION pyruvate is converted to ethanol in two steps pyruvate is reduced directly by NADH to form lactate Beer, wine-making, baking Cheese, yogurt, muscles 31 32  28/09/2023 FACULTATIVE ANAEROBES Yeast, many bacteria Can survive using either fermentation or aerobic respiration Pyruvate is a fork that leads to 2 alternative routes 33 34