Phosphorylation - Biology Junction
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Cellular Respiration Harvesting Chemical Energy ATP AP Biology 2006-2007 What’s the point? The point is to make ATP! ATP AP Biology 2006-2007 Harvesting stored energy Energy is stored in organic molecules carbohydrates, fats, proteins Heterotrophs eat these organic molecules food digest organic molecules to get… raw materials for synthesis fuels for energy controlled release of energy “burning” fuels in a series of step-by-step enzyme-controlled reactions AP Biology Harvesting stored energy Glucose is the model respiration catabolism of glucose to produce ATP glucose + oxygen energy + water + carbon dioxide C6H12O6 + 6O2 ATP + 6H2O + 6CO2 + heat COMBUSTION = making a lot of heat energy by burning fuels in one step fuel AP Biology carbohydrates) RESPIRATION = making ATP (& some heat) by burning fuels in many small steps ATP enzymes O2 ATP O2 CO2 + H2O + ATP (+ heat) glucose CO2 + H2O + heat How do we harvest energy from fuels? Digest large molecules into smaller ones break bonds & move electrons from one molecule to another as electrons move they “carry energy” with them that energy is stored in another bond, released as heat or harvested to make ATP loses e- gains e- + oxidized reduced + + eoxidation AP Biology e- – ereduction redox How do we move electrons in biology? Moving electrons in living systems electrons cannot move alone in cells electrons move as part of H atom e p move H = move electrons loses e- gains e- oxidized + + oxidation reduced + – H reduction H oxidation C6H12O6 + AP Biology H e- 6O2 6CO2 + 6H2O + ATP reduction Coupling oxidation & reduction REDOX reactions in respiration release energy as breakdown organic molecules break C-C bonds strip off electrons from C-H bonds by removing H atoms C6H12O6 CO2 = the fuel has been oxidized electrons attracted to more electronegative atoms in biology, the most electronegative atom? O2 H2O = oxygen has been reduced O couple REDOX reactions & 2 use the released energy to synthesize ATP oxidation C6H12O6 + AP Biology 6O2 6CO2 + 6H2O + ATP reduction Oxidation & reduction Oxidation Reduction adding O removing H loss of electrons releases energy exergonic removing O adding H gain of electrons stores energy endergonic oxidation C6H12O6 + 6O2 6CO2 + 6H2O + ATP reduction AP Biology like $$ in the bank Moving electrons in respiration Electron carriers move electrons by shuttling H atoms around NAD+ NADH (reduced) FAD+2 FADH2 (reduced) NAD+ nicotinamide Vitamin B3 niacin O– O – P –O O phosphates O– O – P –O O AP Biology H reducing power! NADH O H H C NH2 N+ + adenine ribose sugar C NH2 reduction O– – – oxidation O P O O O– O – P –O O carries electrons as H O a reduced molecule N+ How efficient! Build once, use many ways Overview of cellular respiration 4 metabolic stages Anaerobic respiration 1. Glycolysis respiration without O2 in cytosol Aerobic respiration respiration using O2 in mitochondria 2. Pyruvate oxidation 3. Krebs cycle 4. Electron transport chain C H O6 + AP Biology 6 12 6O2 ATP + 6H2O + 6CO2 (+ heat) What’s the point? The point is to make ATP! ATP AP Biology 2006-2007 H+ And how do we do that? H+ H+ H+ H+ H+ H+ H+ ATP synthase enzyme H+ flows through it conformational changes bond Pi to ADP to make ATP set up a H+ gradient allow the H+ to flow down concentration gradient through ATP synthase ADP + Pi ATP APBut… Biology How ADP + P ATP is the proton (H+) gradient formed? H+ H+ Got to wait until the sequel! Got the Energy? Ask Questions! H+ H+ H+ H+ H+ H+ H+ ADP + P ATP AP Biology H+ 2006-2007 Cellular Respiration Stage 2 & 3: Oxidation of Pyruvate Krebs Cycle AP Biology 2006-2007 Overview 10 reactions glucose C-C-C-C-C-C 2 ATP 2 ADP convert fructose-1,6bP glucose (6C) to P-C-C-C-C-C-C-P 2 pyruvate (3C) DHAP G3P produces: 4 ATP & 2 NADH P-C-C-C C-C-C-P 2H consumes: 2Pi 2 ATP net: 2Pi 2 ATP & 2 NADH AP Biology pyruvate C-C-C 2 NAD+ 2 4 ADP 4 ATP Glycolysis is only the start Glycolysis glucose pyruvate 6C 2x 3C Pyruvate has more energy to yield 3 more C to strip off (to oxidize) if O2 is available, pyruvate enters mitochondria enzymes of Krebs cycle complete the full oxidation of sugar to CO2 pyruvate CO2 AP Biology 3C 1C Cellular respiration AP Biology Mitochondria — Structure Double membrane energy harvesting organelle smooth outer membrane highly folded inner membrane cristae intermembrane space fluid-filled space between membranes matrix inner fluid-filled space DNA, ribosomes enzymes free in matrix & What cells would have AP Biology a lot of mitochondria? outer intermembrane membrane inner membrane-bound space membrane cristae matrix mitochondrial DNA Mitochondria – Function Oooooh! Form fits function! Dividing mitochondria Membrane-bound proteins Who else divides like that? Enzymes & permeases bacteria! What does this tell us about the evolution of eukaryotes? Endosymbiosis! AP Biology Advantage of highly folded inner membrane? More surface area for membranebound enzymes & permeases Oxidation of pyruvate Pyruvate enters mitochondrial matrix [ 2x pyruvate acetyl CoA + CO2 3C 2C 1C NAD Where does the CO2 go? Exhale! 3 step oxidation process releases 2 CO2 (count the carbons!) reduces 2 NAD 2 NADH (moves e ) produces 2 acetyl CoA Acetyl CoA enters Krebs cycle AP Biology ] Pyruvate oxidized to Acetyl CoA reduction NAD+ Pyruvate C-C-C [ Coenzyme A CO2 Acetyl CoA C-C oxidation 2 x Yield = 2C sugar + NADH + CO2 AP Biology ] Krebs cycle 1937 | 1953 aka Citric Acid Cycle in mitochondrial matrix 8 step pathway Hans Krebs each catalyzed by specific enzyme 1900-1981 step-wise catabolism of 6C citrate molecule Evolved later than glycolysis does that make evolutionary sense? bacteria 3.5 billion years ago (glycolysis) free O2 2.7 billion years ago (photosynthesis) eukaryotes 1.5 billion years ago (aerobic AP Biology respiration = organelles mitochondria) Count the carbons! pyruvate 3C 2C 6C 4C This happens twice for each glucose molecule 4C citrate oxidation of sugars 4C 6C CO2 x2 4C AP Biology acetyl CoA 5C 4C CO2 Count the electron carriers! pyruvate 3C 6C 4C NADH This happens twice for each glucose molecule 2C 4C citrate reduction of electron carriers x2 4C FADH2 4C AP Biology acetyl CoA ATP CO2 NADH 6C CO2 NADH 5C 4C CO2 NADH Whassup? So we fully oxidized glucose C6H12O6 CO2 & ended up with 4 ATP! What’s the point? AP Biology Electron Carriers = Hydrogen Carriers H+ Krebs cycle produces large quantities of electron carriers NADH FADH2 go to Electron Transport Chain! AP Biology What’s so important about electron carriers? H+ H+ H+ + H+ H H+ H+ ADP + Pi ATP H+ Energy accounting of Krebs cycle 4 NAD + 1 FAD 4 NADH + 1 FADH2 2x pyruvate CO2 3C 3x 1C 1 ADP 1 ATP ATP Net gain = 2 ATP = 8 NADH + 2 FADH2 AP Biology Value of Krebs cycle? If the yield is only 2 ATP then how was the Krebs cycle an adaptation? value of NADH & FADH2 electron carriers & H carriers reduced molecules move electrons reduced molecules move H+ ions to be used in the Electron Transport Chain like $$ in the bank AP Biology What’s the point? The point is to make ATP! ATP AP Biology 2006-2007 H+ And how do we do that? H+ H+ H+ H+ H+ H+ H+ ATP synthase set up a H+ gradient allow H+ to flow through ATP synthase powers bonding of Pi to ADP ADP + P ADP + Pi ATP ATP H+ AP Biology But… Have we done that yet? NO! The final chapter to my story is next! Any Questions? AP Biology 2006-2007 Cellular Respiration Stage 4: Electron Transport Chain AP Biology 2006-2007 Cellular respiration AP Biology What’s the point? The point is to make ATP! ATP AP Biology 2006-2007 ATP accounting so far… Glycolysis 2 ATP Kreb’s cycle 2 ATP Life takes a lot of energy to run, need to extract more energy than 4 ATP! There’s got to be a better way! I need a lot more ATP! AP Biology A working muscle recycles over 10 million ATPs per second There is a better way! Electron Transport Chain series of proteins built into inner mitochondrial membrane along cristae transport proteins & enzymes transport of electrons down ETC linked to pumping of H+ to create H+ gradient yields ~36 ATP from 1 glucose! only in presence of O2 (aerobic respiration) AP Biology That sounds more like it! O2 Mitochondria Double membrane outer membrane inner membrane highly folded cristae enzymes & transport proteins intermembrane space fluid-filled space between membranes AP Biology Oooooh! Form fits function! Electron Transport Chain Inner mitochondrial membrane Intermembrane space C Q NADH dehydrogenase cytochrome bc complex Mitochondrial matrix AP Biology cytochrome c oxidase complex Remember the Electron Carriers? Glycolysis glucose Krebs cycle G3P 2 NADH Time to break open the piggybank! AP Biology 8 NADH 2 FADH2 Electron Transport Chain Building proton gradient! NADH NAD+ + H e p intermembrane space H+ H+ H e- + H+ C e– NADH H FADH2 NAD+ NADH dehydrogenase inner mitochondrial membrane e– Q AP Biology H+ e– H FAD 2H+ + cytochrome bc complex 1 2 O2 H2O cytochrome c oxidase complex mitochondrial matrix What powers the proton (H+) pumps?… Stripping H from Electron Carriers Electron carriers pass electrons & H+ to ETC H cleaved off NADH & FADH2 electrons stripped from H atoms H+ (protons) electrons passed from one electron carrier to next in mitochondrial membrane (ETC) flowing electrons = energy to do work transport proteins in membrane pump H+ (protons) across inner membrane to intermembrane space H+ + H H+ TA-DA!! Moving electrons do the work! + H H+ H+ + H+ H+ H + H+ H H+ C e– NADH AP Biology + H H+ Q e– FADH2 FAD NAD+ NADH dehydrogenase e– 2H+ cytochrome bc complex + 1 2 O2 H2O cytochrome c oxidase complex ADP + Pi ATP H+ But what “pulls” the electrons down the ETC? H 2O O2 AP Biology electrons flow downhill to O2 oxidative phosphorylation Electrons flow downhill Electrons move in steps from carrier to carrier downhill to oxygen each carrier more electronegative controlled oxidation controlled release of energy make ATP instead of fire! AP Biology “proton-motive” force We did it! Set up a H+ H+ H+ H+ gradient Allow the protons to flow through ATP synthase Synthesizes ATP ADP + Pi ATP Are we there yet? AP Biology H+ H+ H+ H+ H+ ADP + Pi ATP H+ Chemiosmosis The diffusion of ions across a membrane build up of proton gradient just so H+ could flow through ATP synthase enzyme to build ATP Chemiosmosis links the Electron Transport Chain to ATP synthesis So that’s the point! AP Biology 1961 | 1978 Peter Mitchell Proposed chemiosmotic hypothesis revolutionary idea at the time proton motive force 1920-1992 AP Biology Pyruvate from cytoplasm Inner + mitochondrial H membrane H+ Intermembrane space Electron transport C system Q NADH Acetyl-CoA 1. Electrons are harvested and carried to the transport system. NADH Krebs cycle e- e- FADH2 e- 2. Electrons provide energy to pump protons across the membrane. e- H2O 3. Oxygen joins with protons to form water. 1 O 2 +2 2H+ O2 H+ CO2 ATP Mitochondrial matrix AP Biology H+ ATP ATP 4. Protons diffuse back in down their concentration gradient, driving the synthesis of ATP. H+ ATP synthase Cellular respiration 2 ATP AP Biology + 2 ATP + ~36 ATP Summary of cellular respiration C6H12O6 + 6O2 6CO2 + 6H2O + ~40 ATP Where did the glucose come from? Where did the O2 come from? Where did the CO2 come from? Where did the CO2 go? Where did the H2O come from? Where did the ATP come from? What else is produced that is not listed in this equation? Why do we breathe? AP Biology Taking it beyond… What is the final electron acceptor in H+ H+ H+ C Electron Transport Chain? e– NADH O2 Q e– FADH2 FAD NAD+ NADH dehydrogenase e– 2H+ + cytochrome bc complex 1 2 O2 H2O cytochrome c oxidase complex So what happens if O2 unavailable? ETC backs up nothing to pull electrons down chain NADH & FADH2 can’t unload H AP Biology ATP production ceases cells run out of energy and you die! What’s the point? The point is to make ATP! ATP AP Biology 2006-2007 Chapter 9. Cellular Respiration Other Metabolites & Control of Respiration AP Biology 2005-2006 Cellular respiration AP Biology 2005-2006 Beyond glucose: Other carbohydrates Glycolysis accepts a wide range of carbohydrates fuels polysaccharides glucose hydrolysis ex. starch, glycogen other 6C sugars glucose modified ex. galactose, fructose AP Biology 2005-2006 Beyond glucose: Proteins Proteins amino acids hydrolysis waste H O H | || N —C— C—OH | H R amino group = waste product excreted as ammonia, urea, or uric acid AP Biology glycolysis Krebs cycle carbon skeleton = enters glycolysis or Krebs cycle at different stages 2005-2006 Beyond glucose: Fats Fats hydrolysis glycerol & fatty acids glycerol (3C) PGAL glycolysis fatty acids 2C acetyl acetyl Krebs groups coA cycle glycerol enters glycolysis as AP PGAL Biology fatty acids enter Krebs cycle as acetyl 2005-2006CoA Carbohydrates vs. Fats Fat generates 2x ATP vs. carbohydrate more C in gram of fat more O in gram of carbohydrate so it’s already partly oxidized fat carbohydrate AP Biology 2005-2006 Metabolism Coordination of digestion & synthesis by regulating enzyme Digestion digestion of carbohydrates, fats & proteins all catabolized through same pathways enter at different points AP Biology CO2 cell extracts energy from every source 2005-2006 Metabolism Coordination of digestion & synthesis by regulating enzyme Synthesis enough energy? build stuff! cell uses points in glycolysis & Krebs cycle as links to pathways for synthesis run the pathways “backwards” eat too much fuel, build fat pyruvate glucose Krebs cycle intermediaries AP Biology acetyl CoA Cells are versatile & thrifty amino acids fatty acids 2005-2006 Carbohydrate Metabolism The many stops on the Carbohydrate Line gluconeogenesis AP Biology 2005-2006 Lipid Metabolism The many stops on the Lipid Line AP Biology 2005-2006 Amino Acid Metabolism The many stops on the AA Line AP Biology 2005-2006 Nucleotide Metabolism The many stops on the GATC Line AP Biology 2005-2006 Control of Respiration Feedback Control AP Biology 2005-2006 Feedback Inhibition Regulation & coordination of production production is self-limiting final product is inhibitor of earlier step allosteric inhibitor of earlier enzyme no unnecessary accumulation of product ABCDEFG 1 2 3 4 5 6 X enzyme enzyme enzyme enzyme enzyme enzyme AP Biology allosteric inhibitor of enzyme 12005-2006 Respond to cell’s needs Key points of control phosphofructokinase allosteric regulation of enzyme “can’t turn back” step before splitting glucose AMP & ADP stimulate ATP inhibits citrate inhibits Why is this regulation important? Balancing act: availability of raw materials vs. energy AP Biologydemands vs. synthesis 2005-2006 A Metabolic economy Basic principles of supply & demand regulate metabolic economy balance the supply of raw materials with the products produced these molecules become feedback regulators they control enzymes at strategic points in glycolysis & Krebs cycle AMP, ADP, ATP regulation by final products & raw materials levels of intermediates compounds in the pathways regulation of earlier steps in pathways levels of other biomolecules in body regulates rate of siphoning off to synthesis pathways AP Biology 2005-2006 It’s a Balancing Act Balancing synthesis with availability of both energy & raw materials is essential for survival! AP Biology do it well & you survive longer you survive longer & you have more offspring you have more offspring & you get to “take over the world” Acetyl CoA is central to both energy production & synthesis make ATP or store it2005-2006 as fat Any Questions?? AP Biology 2005-2006
