Making energy! ATP The point is to make ATP! AP Biology 2008- The energy needs of life Organisms are endergonic systems What do we need energy for? synthesis building biomolecules reproduction movement active transport temperature regulation AP Biology Where do we get the energy from? Work of life is done by energy coupling use exergonic (catabolic) reactions to fuel endergonic (anabolic) reactions digestion + synthesis + AP Biology + energy + energy ATP Adenosine TriPhosphate modified nucleotide nucleotide = adenine + ribose + Pi AMP AMP + Pi ADP ADP + Pi ATP adding phosphates is endergonic How efficient! Build once, use many ways AP Biology high energy bonds How does ATP store energy? AMP ADP ATP I think he’s a bit unstable… don’t you? O– O– O – O– O– –O P –O O– P –O O––P OO P––O O– P O– O O O O O Each negative PO4 more difficult to add a lot of stored energy in each bond most energy stored in 3rd Pi 3rd Pi is hardest group to keep bonded to molecule Bonding of negative Pi groups is unstable spring-loaded Pi groups “pop” off easily & release energy AP Biology Instability of its P bonds makes ATP an excellent energy donor How does ATP transfer energy? ADP ATP O– O– O – –O P –O O– P –O O– P O– O O O O– –O P O – + O 7.3 energy ATP ADP releases energy ∆G = -7.3 kcal/mole Fuel other reactions Phosphorylation released Pi can transfer to other molecules destabilizing the other molecules AP Biology enzyme that phosphorylates = “kinase” An example of Phosphorylation… Building polymers from monomers need to destabilize the monomers phosphorylate! H C OH + H C HO H C It’s never that OH simple! + ATP H C AP Biology + P H C HO synthesis +4.2 kcal/mol “kinase” enzyme -7.3 kcal/mol -3.1 kcal/mol enzyme H H C C O H C H H C C OHHO + + H2O ADP P H H C C O + Pi Another example of Phosphorylation… The first steps of cellular respiration beginning the breakdown of glucose to make ATP Those phosphates sure make it uncomfortable around here! glucose C-C-C-C-C-C hexokinase phosphofructokinase P 2 ATP C C 2 ADP fructose-1,6bP P-C-C-C-C-C-C-P AP Biology DHAP P-C-C-C G3P C-C-C-P H C P activation energy ATP / ADP cycle Can’t store ATP cellular good energy donor, not good energy storage respiration too reactive transfers Pi too easily only short term energy storage carbohydrates & fats are long term energy storage Whoa! Pass me the glucose (and O2)! AP Biology ATP 7.3 kcal/mole ADP + Pi A working muscle recycles over 10 million ATPs per second Cells spend a lot of time making ATP! The point is to make ATP! What’s the point? AP Biology Cellular Respiration Harvesting Chemical Energy ATP AP Biology 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 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+ Phosphorylation SUBSTRATE LEVEL ADP receives a phosphate directly from another molecule (a phosphorylated intermediate) AP Biology OXIDATIVE Oxidation of substrate releases energy; energy is used to create ATP through ATP synthase 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) Cellular Respiration Stage 1: Glycolysis AP Biology 2007- What’s the point? The point is to make ATP! ATP AP Biology Where does it occur? The process of glycolysis occurs within the cell . . . but where? Glucose enters the cell through the plasma membrane (facilitated diffusion) Once it gets in the cell, glycolysis occurs within the cytoplasm Enzymes will couple with the glucose to enact all the necessary steps AP Biology Glycolysis Breaking down glucose “glyco – lysis” (splitting sugar) glucose pyruvate 2x 3C 6C ancient pathway which harvests energy where energy transfer first evolved transfer energy from organic molecules to ATP still is starting point for ALL cellular respiration but it’s inefficient generate only 2 ATP for every 1 glucose occurs in cytosol AP Biology That’s not enough ATP for me! In the cytosol? Why does that make evolutionary sense? Evolutionary perspective Prokaryotes first cells had no organelles Enzymes of glycolysis are “well-conserved” Anaerobic atmosphere life on Earth first evolved without free oxygen (O2) in atmosphere energy had to be captured from organic molecules in absence of O2 Prokaryotes that evolved glycolysis are ancestors of all modern life AP Biology ALL cells still utilize glycolysis You mean we’re related? Do I have to invite them over for the holidays? Overview glucose C-C-C-C-C-C 10 reactions enzyme 2 ATP enzyme 2 ADP convert fructose-1,6bP glucose (6C) to P-C-C-C-C-C-C-P enzyme enzyme 2 pyruvate (3C) enzyme DHAP G3P produces: 4 ATP & 2 NADH P-C-C-C C-C-C-P 2H consumes: 2Pi enzyme 2 ATP enzyme net yield: 2Pi enzyme 2 ATP & 2 NADH DHAP = dihydroxyacetone phosphate AP Biology G3P = glyceraldehyde-3-phosphate pyruvate C-C-C 2 NAD+ 2 4 ADP 4 ATP Glycolysis summary endergonic invest some ATP ENERGY INVESTMENT -2 ATP ENERGY PAYOFF G3P C-C-C-P 4 ATP exergonic harvest a little ATP & a little NADH like $$ in the bank NET YIELD AP Biology net yield 2 ATP 2 NADH 1st half of glycolysis (5 reactions) Glucose “priming” get glucose ready to split phosphorylate CH2 O O P Glucose 6-phosphate 2 P O ADP CH2 O O P CH2 CH2 CH2OH O Fructose 1,6-bisphosphate O CH2 C 4,5 aldolase isomerase O Dihydroxyacetone CH2OH phosphate Glyceraldehyde 3 -phosphate (G3P) Pi NAD+ Pi 6 glyceraldehyde NADH NADH 3-phosphate P dehydrogenase 1,3-Bisphosphoglycerate 1,3-Bisphosphoglycerate (BPG) (BPG) H C O CHOH CH2 O NAD+ AP Biology O Fructose 6-phosphate 3 ATP phosphofructokinase split destabilized glucose P ADP phosphoglucose isomerase glucose molecular rearrangement CH2OH Glucose 1 ATP hexokinase O P O CHOH CH2 O P O P 2nd half of glycolysis (5 reactions) DHAP P-C-C-C Energy Harvest NADH production G3P donates H oxidizes the sugar reduces NAD+ NAD+ NADH NAD+ Pi phosphorylation” ADP ATP AP Biology NAD+ NADH 7 phosphoglycerate kinase ADP ATP 3-Phosphoglycerate (3PG) ADP ATP 3-Phosphoglycerate (3PG) 8 phosphoglyceromutase 2-Phosphoglycerate (2PG) Phosphoenolpyruvate (PEP) CHOH CH2 O P C O H C O CH2OH P OH2O Phosphoenolpyruvate (PEP) 10 pyruvate kinase ADP ATP Pyruvate C C O O CH2 OC ATP Pyruvate OC O- 2-Phosphoglycerate (2PG) 9 enolase H2O ADP Payola! Finally some ATP! Pi 6 NADH ATP production G3P pyruvate PEP sugar donates P “substrate level G3P C-C-C-P O C O CH3 P Substrate-level Phosphorylation In the last steps of glycolysis, where did the P come from to make ATP? 9 the sugar substrateH O(PEP) enolase OH2O 2 P is transferred from PEP to ADP kinase enzyme ADP ATP AP Biology Phosphoenolpyruvate (PEP) ADP Phosphoenolpyruvate (PEP) 10 pyruvate kinase Pyruvate I get it! The Pi came directly from the substrate! Pyruvate C CH2 O O OC ATP ATP ATP ADP C O C O CH3 P Energy accounting of glycolysis 2 ATP 2 ADP glucose pyruvate 2x 3C 6C 4 ADP 4 ATP 2 NAD+ 2 Net gain = 2 ATP + 2 NADH All that work! And that’s all I get? But glucose has so much more to give! some energy investment (-2 ATP) small energy return (4 ATP + 2 NADH) AP 1Biology 6C sugar 2 3C sugars Is that all there is? Not a lot of energy… for 1 billon years+ this is how life on Earth survived no O2 = slow growth, slow reproduction only harvest 3.5% of energy stored in glucose more carbons to strip off = more energy to harvest O2 O2 O2 O2 AP Biology O2 glucose pyruvate 2x 3C 6C Hard way to make a living! But can’t stop there! G3P DHAP NAD+ raw materials products Pi + NADH NAD NADH Pi 1,3-BPG NAD+ Pi + NADH NAD 1,3-BPG NADH 7 ADP Glycolysis 6 Pi ADP ATP ATP 3-Phosphoglycerate (3PG) 3-Phosphoglycerate (3PG) 2-Phosphoglycerate (2PG) 2-Phosphoglycerate (2PG) glucose + 2ADP + 2Pi + 2 NAD+ 2 pyruvate + 2ATP + 2NADH 8 Going to run out of NAD+ 9 H2O without regenerating NAD+, energy production would stop! Phosphoenolpyruvate (PEP) another molecule must accept HADP 10 from NADH ATP so AP Biology NAD+ is freed up for another round Pyruvate H2O Phosphoenolpyruvate (PEP) ADP ATP Pyruvate How is NADH recycled to NAD+? Another molecule must accept H from NADH H2O O2 recycle NADH with oxygen without oxygen aerobic respiration anaerobic respiration “fermentation” pyruvate NAD+ NADH acetyl-CoA CO2 NADH NAD+ lactate acetaldehyde NADH NAD+ lactic acid fermentation which path you use depends on AP Biology who you are… Krebs cycle ethanol alcohol fermentation Pyruvate is a branching point Pyruvate O2 O2 fermentation anaerobic respiration mitochondria Krebs cycle aerobic respiration AP Biology H+ And how do we make ATP? 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? Glycolysis 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 Cellular Respiration Stage 2 & 3: Oxidation of Pyruvate Krebs Cycle AP Biology 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? Endosymbiotic Theory! 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- 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? Cellular Respiration Stage 4: Electron Transport Chain AP Biology 2006- Cellular respiration AP Biology 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! Fermentation (anaerobic) Bacteria, yeast pyruvate ethanol + CO2 3C NADH 2C NAD+ beer, wine, bread 1C back to glycolysis Animals, some fungi pyruvate lactic acid 3C NADH AP Biology 3C NAD+back to glycolysis cheese, anaerobic exercise (no O2) Alcohol Fermentation pyruvate ethanol + CO2 3C NADH 2C NAD+ back to glycolysis Dead end process at ~12% ethanol, kills yeast can’t reverse the reaction Count the carbons! AP Biology 1C bacteria yeast recycle NADH Lactic Acid Fermentation pyruvate lactic acid 3C NADH 3C NAD+ back to glycolysis Reversible process once O2 is available, lactate is converted back to pyruvate by the liver Count the carbons! AP Biology O2 animals some fungi recycle NADH What’s the point? The point is to make ATP! ATP AP Biology 2006- Heat O2 H2O CO2 Glucose Pyruvate AP Biology Electron Transport System NAD+ ATP NADH ATP MITOCHONDRION