Cellular Respiration PDF

Topic 9: Cellular Respiration Cellular respiration, electron transport and oxidative phosphorylation PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Learning ob...

Topic 9: Cellular Respiration Cellular respiration, electron transport and oxidative phosphorylation PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Learning objectives (LOBs) 1. Identify the structure and function of the mitochondria. 2. Identify the location of the different stages of cell respiration in animal cells. 3. Explain how organisms derive and utilize energy through cellular respiration (3 stages: glycolysis, Krebs cycle, oxidative phosphorylation). 4. Describe the process of chemiosmosis in mitochondria, including the electron transport chain and ATP production. 5. Describe the processes of alcohol fermentation and lactic acid fermentation. 6. Compare aerobic to anaerobic respiration in organisms. Reading: Campbell Biology, Chapter 10 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cellular Respiration: harvesting chemical energy Cells need energy from outside sources to perform various tasks such as: - synthesis of macromolecules - active transport - movement - reproduction Catabolic pathways: energy production (ΑΤΡ) by breaking down organic compounds (e.g. cellular respiration) Αnabolic pathways: energy consumption for the synthesis of organic compounds (biosynthesis; e.g. photosynthesis) Energy production and conversion organelles : mitochondria and chloroplasts Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Sunlight is the ultimate source of energy for all Energy flows into an Light energy ecosystem as sunlight and exits ECOSYSTEM as heat Energy source: the Photosynthesis in chloroplasts sun Organic CO2 + H2O + O2 Cellular respiration molecules Photosynthesis: in in mitochondria chloroplasts Cellular respiration: in mitochondria ATP powers most cellular work Heat Figure 10.2 energy Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Catabolic pathways: Production of ATP Cells must regenerate ATP in order to keep working Catabolic pathways produce energy by oxidizing organic fuels The breakdown of organic molecules is exergonic (ΔG < 0) – releases energy (as ATP) – the reactants are more energy-rich than the products (Ginitial > Gfinal) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Catabolic Pathways: Production of ATP 2 major cellular catabolic processes: Cellular respiration (aerobic respiration): – the most prevalent and efficient catabolic pathway – complete degradation of carbohydrates in the presence of oxygen (aerobic) – Yields high amount of ATP Anaerobic respiration (Fermentation): - partial degradation of carbohydrates in the absence of oxygen – Yields low amount of ATP Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Cellular respiration Cellular respiration: - includes both aerobic and anaerobic respiration - Usually refers to aerobic respiration Energy conversion during cellular respiration: - the chemical energy in glucose bonds is transferred to the phosphate bonds in adenosine triphosphate (ATP) The energy from ATP hydrolysis (exergonic reaction) can then be used to perform cellular work (endergonic reactions) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Photosynthesis and Cellular Respiration Photosynthesis: sunlight CO2 + H2O C6H12O6 + O2 Cellular respiration (aerobic): C6H12O6 + Ο2 CO2 + H2O + ΑΤP energy Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Adenosine triphosphate (ATP) ATP =nucleotide that stores energy (in phosphate bonds) Adenosine triphosphate ATP Energy Energy Adenosine diphosphate Pi ADP Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Photosynthesis and Cellular Respiration Molecule and energy exchange Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Mitochondria and Chloroplasts Energy production and conversion organelles Cellular respiration: energy production from the oxidation of organic compounds Chloroplasts: photosynthesis (light and dark reactions) Mitochondria: 2 out of 3 stages of cellular respiration 1. Glycolysis: in the cytosol 2. Krebs cycle (citric acid cycle): in mitochondrial matrix 3. Οxidative phosphorylation: in the inner mitochondrial membrane Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Mitochondria: structure Diameter: 1-10 μm Structure: - Outer membrane: porins, some enzymes (e.g. MAO) - Inner membrane: cristae formation (contains ETC complexes, ATP synthase) - Intermembrane space - Matrix: contains mtDNA and free ribosomes Electron transport chain (ΕΤC) Inner membrane Outer membrane Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Mitochondria: structure Mitochondria (EM) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Redox Reactions: Oxidation and Reduction Catabolic pathways yield energy: – Due to the transfer of electrons (energy) – Redox reactions: transfer electrons from one reactant to another by oxidation and reduction Oxidation: a substance loses electrons => oxidized Reduction: a substance gains electrons => reduced Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Examples of redox reactions becomes oxidized (loses electron) Na + Cl Na+ + Cl– becomes reduced (gains electron) becomes oxidized (loses electron) X– + Y X + Y– becomes reduced (gains electron) reducing oxidizing agent agent Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Oxidation of Organic Fuel Molecules During Cellular Respiration During cellular respiration, the fuel (glucose) is oxidized, and O2 is reduced: becomes oxidized becomes reduced (ATP) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  The Stages of Cellular Respiration Respiration consists of three metabolic stages: 1. Glycolysis: anaerobic stage - in the cytosol 2. The citric acid cycle Aerobic stage- 3. Oxidative phosphorylation in mitochondria Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  The Stages of Cellular Respiration Glycolysis: glucose breaks down into 2 molecules of pyruvate The citric acid cycle: Pyruvate is converted to acetyl- CoA which is broken down into CO2 Oxidative phosphorylation: – Driven by the electron transport chain (ETC) – ETC causes chemiosmosis which generates ATP (by ATP synthase) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Production of ATP during cellular respiration Glycolysis and the citric acid cycle: – generate some ATP (10% of total) by substrate-level phosphorylation Enzyme Enzyme ADP P Substrate + ATP Product Figure 10.7 Most ATP (90%) is generated by oxidative phosphorylation (by ATP synthase) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Overview of cellular respiration stages Electrons Electrons carried carried via NADH and via NADH FADH2 Oxidative Citric phosphorylation: Glycolysis acid electron Glucose Pyruvate cycle transport and chemiosmosis Cytosol Mitochondrion ATP ATP ATP Substrate-level Oxidative Substrate-level phosphorylation phosphorylation Figure 10.6 phosphorylation Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Energy transfer via the redox coenzymes NAD+ and FAD Cellular respiration: - Energy from organic compounds is produced in the form of electrons - Electron (energy) transport by redox coenzymes NAD+ and FAD The electrons released from the oxidation of organic compounds (during glycolysis and Krebs cycle): 1. First transferred to the coenzymes NAD+ and FAD => become reduced to NADH and FADH2 2. Then transferred to the electron transport chain (ETC) 3. Finally transferred to O2 => production of H20 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Redox coenzymes ΝΑD and FAD NAD= Nicotinamide adenine dinucleotide FAD= flavin adenine dinucleotide reduction FAD FADH2 oxidation Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  FAD: a redox coenzyme FADH2 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  NAD and FAD: redox coenzymes Dehydrogenases: enzymes that remove e- from organic compounds (become oxidized) and transfer them to NAD+ or FAD  NAD+ becomes reduced to NADH Electrons transferred to the ETC  FAD becomes reduced to FADH2 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  NAD and FAD: redox coenzymes Each e- is co-transferred with a proton (H+) (H H+ + e- ) 2 e– + 2 H+ 2 e– + H+ NAD+ NADH H O Dehydrogenase H H O + 2[H] Reduction of NAD+ + C NH2 C NH2 H+ (from food) Oxidation of NADH N+ Nicotinamide N Nicotinamide O CH2 (oxidized form) (reduced form) O O P O– O H H NAD: redox coenzyme – O P O HO OH NH2 HO O CH2 N N H N N H O H H HO OH Figure 10.4: NAD+ reduction reaction. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Cellular respiration stages 1.Glycolysis 2. Citric acid cycle 3. Oxidative phosphorylation Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Cellular respiration localization (Matrix) (oxidative phosphorylation) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  1. Glycolysis Glycolysis: – Means “splitting of sugar” – Breaks down glucose (6 C) into 2 molecules of pyruvate (3 C) – Occurs in the cytosol of the cell – Anaerobic stage (does not require oxygen) – Products: 2 ATP, 2 NADH, 2 pyruvate molecules – ATP production: by substrate-level phosphorylation Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Glycolysis Glycolysis consists of Glycolysis Citric acid cycle Oxidative phosphorylation two major phases: ATP ATP ATP 1. Energy investment Energy investment phase phase: ATP spent Glucose 1 2. Energy payoff 2 ADP + 2 P 2 ATP used phase: ATP produced Energy payoff phase 2 4 ADP + 4 P 4 ATP formed 2 NAD+ + 4 e- + 4 H + 2 NADH + 2 H+ 2 Pyruvate + 2 H2O Glucose 2 Pyruvate + 2 H2O 4 ATP formed – 2 ATP used 2 ATP + 2 H+ 2 NAD+ + 4 e– + 4 H + 2 NADH Figure 10.8 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Energy investment phase Energy investment phase Glucose 2 ADP + 2 P 2 ATP used 2 ATP spent Substrates are phosphorylated becoming more energy-rich (more unstable) => splitting of glucose Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Energy payoff phase Energy payoff phase 4 ATP 4 ADP + 4 P 4 ATP formed 2 NADH 2 NAD+ + 4 e- + 4 H + 2 NADH + 2 H+ 2 pyruvates 2 Pyruvate + 2 H2O Glucose 2 Pyruvate + 2 H2O 4 ATP formed – 2 ATP used 2 ATP 2 NAD+ + 4 e– + 4 H + 2 NADH + 2 H+ Net products of glycolysis: 2 ATP, 2 NADH, 2 pyruvates Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Glycolysis 6 2 NAD+ Triose phosphate CH2OH dehydrogenase Citric HH H Glycolysis acid Oxidative 2 Pi 2 NADH HO H cycle phosphorylation + 2 H+ HO OH H OH 2 Glucose P O C O CHOH ATP 1 CH2 O P 1, 3-Bisphosphoglycerate Hexokinase 2 ADP ADP 7 Phosphoglycerokinase CH2OH P 2 ATP HH OH OH H 2 O– HO H OH C Glucose-6-phosphate CHOH 2 CH2 O P Phosphoglucoisomerase 3-Phosphoglycerate 8 CH2O P Phosphoglyceromutase O CH2OH H HO 2 O– H HO HO H C O Fructose-6-phosphate H C O P 3 CH2OH ATP 2-Phosphoglycerate Phosphofructokinase (PFK) 9 2H O Enolase ADP 2 2 O– P O CH2 O CH2 O P C O HO C O P H OH HO H CH2 Fructose- Phosphoenolpyruvate 2 ADP 1, 6-bisphosphate 10 4 Pyruvate kinase Aldolase 2 ATP 5 H O– 2 P O CH2 Isomerase C O C O C O CHOH C O CH2OH CH2 O P CH3 Dihydroxyacetone Glyceraldehyde- Pyruvate phosphate 3-phosphate Figure 10.8 B: Energy payoff phase Figure 10.9 A: Energy investment phase Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Citric acid cycle and oxidative phosphorylation Citric acid cycle: in mitochondrial matrix Oxidative phosphorylation: inner mitochondrial membrane 1. Electron transport chain (ETC): located on the inner mitochondrial membrane 2. Chemiosmosis: H+ gradient drives ATP synthesis by ATP synthase (enzyme located on inner mitochondrial membrane)- ATP synthesis takes place in matrix Inner mitochondrial membrane: - Krebs cycle enzymes - Electron transport chain (ETC) enzymes/complexes - ATP synthase complex (F0F1 ATPase) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  2. Citric acid cycle (Krebs cycle/ TCA cycle) Takes place in the mitochondrial matrix The citric acid cycle completes the oxidation of organic molecules => CO2 and energy production Conversion of pyruvate (glycolysis product) into acetyl- CoΑ before the beginning of the citric acid cycle Acetyl-coenzyme A (acetyl-CoA) is produced either by glycolysis or β-οxidation of fatty acids  Acetyl -CoA enters Krebs cycle Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Pyruvate conversion to Acetyl-CoA From fatty acid breakdown (β-oxidation) CYTOSOL MITOCHONDRION NAD+ NADH + H+ O– S CoA From 2 C glycolysis O C O Pyruvate dehydrogenase C O CH3 1 3 CH3 Acetyl CoA Pyruvate CO2 Coenzyme A Transport protein Figure 10.10 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Citric acid cycle Pyruvate is broken down and CO2 is released Acetyl-CoA binds to To ETC oxaloacetate (ΟΑΑ)  citric acid is produced NADH and FADH2 are produced and transferred to the electron transport chain (ETC) To ETC Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Citric acid cycle (Krebs cycle) Krebs cycle products: Each acetyl-CoA that enters the cycle is converted to: - 2 CO2 - 3 NADH - 1 FADH2 - 1 ATP Krebs cycle energy gain: 1 ATP, 3 NADH and 1 FADH2 1 NADH 3 ATP 1 FADH2 2 ATP => Net energy profit : 12 molecules of ATP from 1 Krebs cycle Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Overview of the citric acid cycle 1 glucose molecule Pyruvate Glycolysis Citric Oxidative acid produces 2 pyruvates (from glycolysis, 2 molecules per glucose) cycle phosphorylation upon glycolysis ATP ATP ATP CO2 => 2 acetyl-CoA CoA molecules NADH + 3 H+ Acetyl CoA From one glucose CoA molecule the 2 citric CoA acid cycles generate: 4 CO2 Citric acid 2 CO2 cycle 2 ATP FADH2 3 NAD+ FAD 3 NADH 6 NADH + 3 H+ ADP + P i 2 FADH2 ATP Figure 10.11 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Citric acid cycle Citric Oxidative Glycolysis acid phosphorylation cycle S CoA C O CH3 Acetyl CoA CoA SH NADH O C COO– + H+ CH2 1 COO– H2O COO– CH2 COO– NAD+ 8 Oxaloacetate HO C COO– CH2 CH2 2 COO– HC COO– COO– HO CH HO CH Malate CH2 Figure Citrate 9.12 COO– Isocitrate COO– Citric CO2 3 7 acid NAD+ H2O cycle COO– COO– NADH CH + H+ Fumarate CoA SH CH2 HC CH2 a-Ketoglutarate COO– C O 6 4 COO– CoA SH COO– COO– CH2 5 CH2 FADH2 CH2 CH2 CO2 FAD NAD+ COO– C O Succinate Pi S CoA NADH GTP GDP Succinyl + H+ CoA ADP ATP Figure 10.12 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Overview of the citric acid cycle http://www.youtube.com/watch?v=hw5nWB0xN0Y&feature=related Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  3. Oxidative phosphorylation Oxidative phosphorylation: Electron transport chain and chemiosmosis Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  3. Oxidative phosphorylation Oxidative: NADH and FADH2 donate electrons to the electron transport chain (ETC) Phosphorylation: ETC powers ATP synthesis - Phosphorylation: production of ATP from ADP + Pi (ATP synthase) Chemiosmosis: an energy-coupling mechanism -couples electron transport chain (ETC) to ATP synthesis during oxidative phosphorylation - uses energy from a H+ gradient across a membrane (H+ flow) to drive cellular work (ATP production) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Electron transfer to the electron transport chain Electrons enter the ETC in 2 ways: - NADH oxidation through complex Ι (NADH dehydrogenase) - FADH2 oxidation through complex II (succinate dehydrogenase) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Stepwise Energy Transfer in the Electron Transport Chain Cellular respiration oxidizes glucose in a series of steps If electron transfer is not stepwise a large release of energy occurs H2 + 1/2 O2 Free energy, G Explosive release of (a) Uncontrolled reaction heat and light energy Figure 10.5 A H2O Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Stepwise Energy Transfer in the Electron Transport Chain The electron transport chain: 2H + 1/ 2 O2 – Passes electrons in a (from food via NADH) series of steps instead – Controlled release of 2 H+ + 2 eenergy for synthesis of ATP of in one explosive reaction ATP Free energy, G ATP – Uses the energy from the electron transfer to ATP form ATP – Each e- carrier is more 2 e– 1/ O2 electronegative than the 2 H+ 2 previous one H2O Figure 10.5 B (b) Cellular respiration Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  The electron transport chain Electrons from the oxidation of NADH and FADH2 are transferred to the electron transport chain (ETC) NADH 50 Free energy (G) relative to O2 (kcl/mol) FADH2 1. These electrons from NADH I Multiprotein 40 and FADH2 are initially FMN Fe S Fe S FAD II complexes transferred to ubiquinone CoQ Cyt b III 30 Fe S Cyt c1 2. Electrons passed from higher Cyt c IV Cyt a energy carrier to lower energy 20 Cyt a3 carrier (more electronegative) 10 3. Electrons are eventually transferred to O2 (most electronegative) forming H2O 0 2 H + + 12 O2 Figure 10.13 H2O Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Electron transport chain complexes ΝADH FADH2 Complex ΙI: Complex Ι: Succinate ΝADH dehydrogenase dehydrogenase 1 2. Coenzyme Q (CoQ): ubiquinone 3. Complex ΙΙΙ: cytochrome oxidoreductase 4. Cytochrome c 5. Complex ΙV: cytochrome oxidase Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Oxidative phosphorylation: electron transport chain Intermembrane space Inner mitochondrial membrane matrix Electrons from the oxidation of NADH and FADH2 produced by glycolysis and Krebs cycle are transferred to the Electron Transport Chain (ETC) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Oxidative phosphorylation: electron transport chain O2 accepts the ETC electrons => production of H2O Intermembrane space Matrix Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Oxidative phosphorylation: chemiosmosis ETC causes H+ pumping to the intermembrane space => H+ concentration gradient created Electrochemical gradient between the matrix and the intermembrane space - pH (matrix)= 8 - pH (intermembrane space)=7  membrane potential developed  chemiosmosis Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Oxidative phosphorylation: ΑΤΡ production Η+ concentration is greater at the intermembrane space compared to the matrix => Chemiosmosis: - H+ flow to the matrix through ΑΤΡ-synthase (down their concentration gradient) - ATP-synthase uses the energy from the H+ flow to produce ATP Intermembrane space ΑΤΡ synthase Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Matrix  Proton-motive force: proton gradient is created by the flow of e- ETC does not directly synthesize ATP ETC proteins pump H+ from the mitochondrial matrix to the intermembrane space Proton-motive force (PMF): - proton (H+) gradient created by the flow of e- - Drives chemiosmosis - Stores energy => drives ATP production by ATP synthase Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Chemiosmosis: The Energy-Coupling Mechanism ATP synthase is the enzyme that actually makes ATP ATP synthase functions as a pump running in reverse INTERMEMBRANE SPACE Each H+ that flows H+ A rotor within the membrane spins H+ H+ through ATP synthase clockwise when H+ flows past H+ H+ it down the H+ gradient. causes 120° rotation H+ H+ A stator anchored in the membrane holds the knob stationary. Every 3H+ that flow through ATP A rod (for “stalk”) extending into synthase the knob also spins, activating catalytic sites in the knob. H+ Three catalytic sites in the Synthesis of 1 ADP + stationary knob join inorganic phosphate to ADP to make ATP. ATP molecule Pi ATP MITOCHONDRIAL MATRIX Figure 10.14 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  ATP synthase (F0F1 ATPase) The enzyme responsible for synthesizing ATP from ΑDP and Pi Located in the inner mitochondrial membrane Found in mitochondria, chloroplasts and bacteria Proton pump (Η+): Uses the proton gradient to power ATP synthesis 2 parts: - F0: the transmembrane part - composed of subunits a,b,c - F1: the matrix part - made by subunits α,β,γ,δ,ε Proton flow through ATP synthase => changes the binding affinity of ATP/ADP Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  ATP synthase (F0F1 ATPase) matrix Inner mitochondrial membrane Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  T Binding of ADP and Pi O L ATP synthesis from ADP and Pi 120 CCW rotation due to proton flow and ATP release O= open confirmation L= loose conformation T= tight conformation Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Chemiosmosis and the Electron Transport Chain Inner Mitochondrial Glycolysis Oxidative phosphorylation. membrane electron transport and chemiosmosis ATP ATP ATP 2 H+ 4 H+ 4 H+ 3 H+ Cyt c Protein complex Intermembrane of electron space carners Q IV I III ATP Inner II synthase mitochondrial FADH2 H2O membrane FAD+ 2 H+ + 1/2 O2 NADH+ NAD+ ADP + Pi ATP (Carrying electrons from, food) 3 H+ Mitochondrial Chemiosmosis Electron transport chain matrix + Electron transport and pumping of protons (H ), ATP synthesis powered by the flow + + which create an H gradient across the membrane of H back across the membrane Figure 10.15 Oxidative phosphorylation Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Energy (electron) flow during aerobic respiration Sequence of energy flow during aerobic respiration: Glucose →NADH/ FADH2 → ETC → PMF → ATP – ETC: Electron Transport Chain – PMF: Proton-Motive Force Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Chemiosmosis and Electron Transport Chain Mitochondria use chemical energy to generate ATP by the chemiosmosis mechanism - Redox reactions of electron transport chains generate a H+ gradient across a membrane - ATP synthase uses this proton-motive force to make ATP Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Chemiosmosis localisation in Mitochondria Mitochondria Key Higher [H+] Lower [H+] Electron flow causes Mitochondrion Chloroplast a proton gradient to form in the intermembrane space Intermembrane H+ Diffusion space Electron Membrane transport => ATP is chain synthesized in the ATP Synthase matrix Matrix ADP+ P ATP H+ Figure 11.16 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Chemiosmosis localisation in Mitochondria The spatial organization of chemiosmosis in mitochondria: - The location and orientation of ATP synthase - The proton (H+) accumulation area (proton gradient) ATPase mitochondrion Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Chemiosmosis localisation in Mitochondria Mitochondria Localisation of ATP Inner membrane synthase Orientation of ATP From intermembrane synthase space towards the matrix Proton accumulation Intermembrane space area (proton gradient) Area of ATP synthesis Matrix Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  An Accounting of ATP Production by Cellular Respiration Synthesis of 1 ΑΤP molecule requires flow of 3 protons to the mitochondrial matrix through the ATP synthase Number of protons transferred to the intermembrane space from the oxidation of: - ΝADH: 10 protons => production of 3 ATP molecules but net gain 2.5 molecules of ΑΤΡ - FADH2: 6 protons => production of 2 ATP molecules but net gain 1.5 molecules of ΑΤΡ Note: some ATP (0.25 ATP per 1 ATP) used for transport of ATP produced by oxidative phosphorylation to cytosol (available for cellular work) and some ATP also spent for pyruvate transport from cytosol into the mitochondria Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Explanation: ATP production by NADH= 10H+/3H+ =3.33 ATP molecules ATP production by FADH2= 6H+/3H+ =2 ATP molecules Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  ΑΤΡ production during cellular respiration 38 molecules of ATP produced from 1 glucose molecule Electron shuttles MITOCHONDRION CYTOSOL 2 NADH span membrane or 2 FADH2 2 NADH 2 NADH 6 NADH 2 FADH2 Glycolysis Oxidative 2 Citric phosphorylation: 2 Acetyl acid electron transport Glucose Pyruvate CoA cycle and chemiosmosis + 2 ATP + 2 ATP + about 32 or 34 ATP by substrate-level by substrate-level by oxidative phosphorylation, depending phosphorylation phosphorylation on which shuttle transports electrons from NADH in cytosol (Net gain in cytosol from oxidative About phosphorylation about 26 or 28 ATP) Maximum production per glucose molecule: 36 or 38 ATP Net gain in cytosol: about 30 or 32 ATP Figure 10.16 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Total ATP Production by Cellular Respiration Aerobic cellular respiration has three stages: – Glycolysis Products: 2 pyruvates + 2 ATP+ 2 NADH – Citric acid cycle Products: 3 CO2, 1 ATP, 4 NADH + 1 FADH2 / pyruvate molecule = 6 CO2, 2 ATP, 8 NADH + 2 FADH2 / glucose molecule – Oxidative phosphorylation (electron transport chain): 32 or 34 ATP TOTAL PRODUCTION: 36 or 38 ATP molecules Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Total ATP Production by Cellular Respiration Aerobic respiration stage Energy gain Glycolysis (Glucose → 2 2 ATP+ 2 NADH pyruvates) Pyruvate conversion to Acetyl- 2 NADH CoA (2 pyruvates→ 2 Acetyl-CoA) Citric acid cycle (2 citric acid 2 ATP, 6 NADH + 2 FADH2 cycles for 2 acetyl-CoA produced from 1 glucose molecule) Oxidative phosphorylation 30 ATP (from 10 NADH) and 4 ATP (from 2 FADH2) TOTAL ATP PRODUCTION FROM 38 ATP 1 GLUCOSE MOLECULE DURING AEROBIC RESPIRATION Note: 10 NADH and 2 FADH2 are produced during glycolysis, pyruvate conversion to Acetyl-CoA and the Citric acid cycle. In oxidative phosphorylation: 10 NADH x 3 ATP = 30 ATP and 2 FADH2 x 2 ATP= 4 ATP => 34 total ATP molecules during oxidative phosphorylation Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Net ATP gain in cytosol by Cellular Respiration Aerobic respiration stage Energy gain Glycolysis (Glucose → 2 2 ATP+ 2 NADH pyruvates) Pyruvate conversion to Acetyl- 2 NADH CoA (2 pyruvates→ 2 Acetyl-CoA) Citric acid cycle (2 citric acid 2 ATP, 6 NADH + 2 FADH2 cycles for 2 acetyl-CoA produced from 1 glucose molecule) Oxidative phosphorylation 25 ATP (from 10 NADH) and 3 ATP (from 2 FADH2) NET ATP GAIN FROM 1 32 ATP GLUCOSE MOLECULE DURING AEROBIC RESPIRATION Note: 10 NADH and 2 FADH2 are produced during glycolysis, pyruvate conversion to Acetyl-CoA and the Citric acid cycle. In oxidative phosphorylation: 10 NADH x 2.5 ATP = 25 ATP and 2 FADH2 x 1.5 ATP= 3 ATP => 28 total ATP molecules during oxidative phosphorylation Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings ATP production/gain during cellular respiration ATP molecule numbers are not exact for 3 reasons: 1. Some ATP is spent for moving the ATP produced in the mitochondrion into the cytosol, where it will be used for cellular work 2. ATP production depends on the type of electron shuttle used to transport electrons from cytosolic NADH (produced by glycolysis) to the mitochondrion (to oxidative phosphorylation): Electrons of cytosolic NADH can be passed either to mitochondrial NAD+ (e.g. liver cells) or to mitochondrial FAD (e.g. brain cells) 3. Some energy is used for the active transport of pyruvate (produced by glycolysis) from the cytosol into the mitochondrion Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  ATP production/gain during cellular respiration If electrons from cytosolic NADH (2 NADH from glycolysis) are passed to mitochondrial NAD+ (e.g. liver cells) => production of 6 ATP molecules ( 2 NADH x 3 ATP = 6 ATP) Electron carrier cytosol mitochondrion 2NADH 2NAD+ (cyt) (mit) 2NAD+ 2NADH (cyt) (mit) to ETC If electrons from cytosolic NADH are passed to mitochondrial FAD (e.g. brain cells) => production of 4 ATP molecules ( 2FADH2 x 2 ATP = 4 Electron ATP) cytosol carrier mitochondrion 2NADH 2FAD (cyt) (mit) 2FADH2 to ETC 2NAD+ (cyt) (mit) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Anaerobic respiration Cellular (aerobic) respiration: produces ATP (high amount) in the presence of oxygen Anaerobic respiration: - Produces low amount of ATP in the absence of oxygen (anaerobic conditions) - uses an electron transport chain with an electron acceptor other than O2 (e.g. sulfate) Fermentation: - Special type of anaerobic respiration - uses phosphorylation instead of an electron transport chain to generate ATP Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Anaerobic cellular respiration Production of lower amounts of ΑΤΡ than aerobic cellular respiration (only 2 molecules of ΑΤP) 2 stages: 1. Glycolysis 2. Fermentation Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Aerobic and anaerobic respiration Pyruvate is a key juncture in catabolism Glucose CYTOSOL Pyruvate No O2 present O2 present Fermentation Cellular respiration MITOCHONDRION Ethanol Acetyl CoA or lactate Citric acid cycle Figure 10.18 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Anaerobic cellular respiration 1. Glycolysis: – Can produce ATP with or without oxygen (in aerobic or anaerobic conditions) – In anaerobic conditions it couples with fermentation to produce ATP 2. Fermentation: - Lactic acid or alcohol production - NAD+ regeneration reactions => NAD+ can be reused by glycolysis so that ATP can continue to be generated Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Types of Fermentation Alcohol fermentation: Ethanol and CO2 production in yeasts (unicellular fungi) Lactic acid fermentation: Lactic acid production in animal cells Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Anaerobic respiration: types of fermentation Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Alcohol fermentation Pyruvate is converted to ethanol and CO2 Applications: Wine, beer, bread making depend on this Reaction: C6H12O6 → 2 CH3CH2OH + 2 CO2 ethanol carbon dioxide 2 ADP + 2 P1 2 ATP O– C O C O Glucose Glycolysis CH3 2 Pyruvate 2 NAD+ 2 NADH 2 CO2 H H H C OH C O CH3 CH3 2 Ethanol 2 Acetaldehyde Figure 10.17 (a) Alcohol fermentation Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Alcohol fermentation Yeasts (e.g. Saccharomyces cerevisiae) used to produce ethanol in alcoholic drinks (e.g. beer, wine) Baker’ yeast: special yeast strain (Saccharomyces cerevisiae) used to make bread - CO2 production (alcohol fermentation by-product) causes bread to rise 2 Pyruvate 2 NAD+ 2 NADH 2 CO2 H H H C OH C O CH3 CH3 2 Ethanol 2 Acetaldehyde Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Lactic acid fermentation Lactic acid production in animal cells/ bacteria Pyruvate is reduced directly by NADH to form lactate C6H12O6 → 2 CH3CHOHCOOH Glucose Lactic acid (lactate) 2 ADP + 2 P1 2 ATP Glucose Glycolysis O– C O C O 2 NAD+ 2 NADH O CH3 C O 2 Pyruvate H C OH CH3 Figure 10.17 2 Lactate (b) Lactic acid fermentation Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Lactic acid fermentation Occurs when there is limited presence of oxygen Example: Muscle fatigue under strenuous exercise - large amounts of oxygen are required in muscles due to strenuous exercising - muscles need energy faster than the rate of oxygen supply by blood => Lactic acid fermentation occurs => Lactate accumulation causes muscle fatigue (muscle cramps and stiffness) Application: certain bacteria convert lactose into lactic acid in yogurt (e.g. Lactobacillus) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Lactic acid fermentation Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Comparison of Aerobic and Anaerobic Cellular Respiration Both use glycolysis to oxidize glucose and other organic fuels to pyruvate Different final products (organic compound vs water) Aerobic respiration produces a lot more ATP - Aerobic respiration produces 38 ATP per glucose molecule - Anaerobic respiration (fermentation) produces 2 ATP per glucose molecule Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Anaerobic respiration Obligate anaerobes: microorganisms that carry out fermentation or anaerobic respiration and cannot survive in the presence of O2 Facultative anaerobes: microorganisms that can survive in both the presence and absence of oxygen using either fermentation or aerobic cellular respiration. (e.g. yeasts and many bacteria) => Pyruvate is a fork in the metabolic road that leads to two alternative catabolic routes Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Catabolic pathways connection Catabolic pathways funnel electrons from many kinds of organic molecules into cellular respiration Glycolysis and the citric acid cycle connect to many other metabolic pathways Proteins: Excess amino acids can enter cellular respiration after losing their amino groups (as NH3) Lipids: - Glycerol (in fats) can enter glycolysis - Fatty acids can enter the citric acid cycle as acetyl-CoA (β-oxidation product) Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  The catabolism of various food molecules Proteins Carbohydrates Fats Amino Sugars Glycerol Fatty acids acids Glycolysis Glucose Glyceraldehyde-3- P NH3 Pyruvate Acetyl CoA Citric acid cycle Oxidative Figure 10.19 phosphorylation Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Anabolic Pathways: Biosynthesis Use ATP The body uses small molecules to synthesize other substances Source of small molecules: – directly from food – from glycolysis or the citric acid cycle Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Regulation of Cellular Respiration via Feedback Mechanisms Metabolism is tightly regulated – Supply and demand of intermediates – Energy status – Feedback mechanisms Cellular respiration: - controlled by allosteric enzymes - Feedback inhibition by ATP Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Control of Cellular Respiration Glucose Phosphofructokinase (PFK) AMP Glycolysis is the major control point Fructose-6-phosphate Stimulates + Phosphofructokinase – Allosteric enzyme – – Fructose-1,6-bisphosphate Inhibits Inhibits – Inhibited by ATP – Inhibited by citrate – Stimulated by AMP Pyruvate ATP Citrate Acetyl CoA Citric acid cycle Oxidative Figure 10.20 phosphorylation Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Clinical correlations Diseases caused by insufficient synthesis of ATP (e.g. due ATP synthase mutations): => Severe neuromuscular disorders (e.g. Leigh and ΜΕLAS syndromes- cause severe encephalopathy) - Cardiomyopathies, encephalomyopathies, etc - Example: Leber’s optic neuropathy- due to Complex I mutations Symptoms in early childhood Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Summary Mitochondria: structure and function (respiration) 3 stages of cellular respiration (and location): Glycolysis - cytosol Krebs cycle –mitochondrial matrix Oxidative phosphorylation: ETC – inner mitochondrial membrane, ATP synthesis- matrix Anaerobic respiration: Alcohol fermentation (bread, beer) Lactic acid fermentation (muscles, bacteria in yogurt) Aerobic vs anaerobic respiration comparison Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Videos Krebs cycle: http://www.youtube.com/watch?v=hw5nWB0xN0Y&feature=r elated Fermentation: http://www.youtube.com/watch?v=StXlo1W3Gvg&feature=rel ated Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Glycolysis animation http://www.science.smith.edu/departments/Biology/Bio231/glycol ysis.html Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Glycolysis animation http://highered.mcgraw- hill.com/sites/0072507470/student_view0/chapter25/animation__how_ glycolysis_works.html Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings  Oxidative phosphorylation http://highered.mcgraw- hill.com/sites/0072507470/student_view0/chapter25/animation__electr on_transport_system_and_atp_synthesis__quiz_1_.html Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings