Honors Biology Cell Respiration PDF

Cellular Respiration Harvesting Chemical Energy ATP Honors Biology  Harvesting stored energy ▪ Glucose is the model ◆ catabolism of glucose to produce ATP respiration glucose + oxygen → energy + water + carbon...

Cellular Respiration Harvesting Chemical Energy ATP Honors Biology  Harvesting stored energy ▪ Glucose is the model ◆ catabolism of glucose to produce ATP respiration glucose + oxygen → energy + water + carbon dioxide C6H12O6 + 6O2 → ATP + 6H2O + 6CO2 + heat combustion = making a lot of heat energy respiration = making ATP (& some heat) by burning fuels in one step by burning fuels A in many small steps T P enzymes AT O glu O P 2 cos fuel Honors Biology (carbohydrates) CO2 + H2O + heat e CO2 +2 H2O + ATP (+ 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 + – + e + e - - oxidation reduction e Honors Biology - redox  Overview of cellular respiration ▪ 4 metabolic stages ◆ Anaerobic respiration 1. Glycolysis ⬥ respiration without O2 ⬥ in cytoplasm ◆ Aerobic respiration ⬥ respiration using O2 ⬥ in mitochondria 2. Pyruvate oxidation 3. Krebs cycle 4. Electron transport chain C6H12O6 + Honors Biology 6O2 → ATP + 6H2O + 6CO2 (+ heat)  Cellular Respiration Stage 1: Glycolysis Honors Biology  Glycolysis ▪ Breaking down glucose ◆ “glyco – lysis” (splitting sugar) glucose → → → → → 6 pyruvate 3 2x C C ◆ 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 cytoplasm Honors Biology  Glycolysis summary ENERGY INVESTMENT endergonic invest some ATP G3P ENERGY PAYOFF C-C-C-P exergonic 4A harvest a little TP ATP & a little NADH like $$ in the bank NET YIELD yield 2 ATP Honors Biology 2 NADH  Energy accounting of glycolysis 2 ATP 2 ADP glucose → → → → → pyruvate 6 3 2x C C AT 4 ADP 4 P ▪ Net gain = 2 ATP ◆ some energy investment (-2 ATP) ◆ small energy return (+4 ATP) ▪ 1 6C sugar → 2 3C sugars Honors Biology  Is that all there is? ▪ Not a lot of energy… ◆ for 1 billion 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 glucose → → → → pyruvate 6 3 2x C C O2 O2 Honors Biology O2  We can’t stop there! Glycolysis glucose + 2ADP + 2Pi + 2 NAD+ → 2 pyruvate + 2ATP + 2NADH ▪ Going to run out of NAD+ ◆ without regenerating NAD+, recycl energy production would stop! e ◆ another molecule must accept NADH H from NADH Honors Biology  Pyruvate is a branching point Pyruvate O2 O2 fermentation anaerobic respiration mitochondria Kreb’s cycle aerobic respiration Honors Biology  Fermentation (anaerobic) ▪ Bacteria, yeast pyruvate → ethanol + CO2 3 2 1 CNADH NAD+C C to glycolysis→→ ▪ beer, wine, bread ▪ Animals, some fungi pyruvate → lactic acid 3 3 CNADH C NAD+to glycolysis→→ ▪ cheese, Honors Biology anaerobic exercise (no O2)  Cellular Respiration Stage 2 & 3: Oxidation of Pyruvate Krebs Cycle Honors Biology  Glycolysis is only the start ▪ Glycolysis glucose → → → → → 6 pyruvate 3 2x C C ▪ 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 → → → → → → 3 CO2 1 Honors Biology C C  Cellular respiration Honors 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 outer intermembrane membrane inner ◆ enzymes space membrane cristae matrix What Honorscells would have Biology mitochondria a lot of mitochondria? l  Mitochondria – Function Dividing mitochondria Membrane-bound proteins Who else divides like that? Enzymes & permeases What does this tell us about Advantage of highly folded inner the evolution of eukaryotes? membrane? Endosymbiosis! More surface area for Honors Biology membrane-bound enzymes  Pyruvate oxidized to Acetyl CoA N A reduction D+ C Coenzyme A Acetyl CoA Pyruvate O C-C C-C-C 2oxidation [ 2 x Yield = 2C sugar + NADH + CO2 Honors Biology ]  1937 | 1953 Krebs cycle ▪ 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 Honors Biology respiration = organelles → mitochondria)  Count the carbons! pyruvate acetyl CoA 3C 2C citrate 4C 6C 4C x2 6C This happens twice for each oxidation glucose of sugars CO2 molecule 5C 4C 4C 4C CO2 Honors Biology  Count the electron carriers! CO2 pyruvate acetyl CoA 3C 2C NADH citrate NADH 4C 6C 4C x2 6C This happens twice for each reduction CO2 glucose of electron molecule carriers NADH 4C 5C FADH2 CO2 4C AT 4C Honors Biology NADH P  Electron Carriers = Hydrogen Carriers H+ H+ ▪ Krebs cycle H+ H+ + H+ H+ H H+ produces large quantities of AD electron carriers P A + Pi T ◆ NADH P H+ ◆ FADH2 ◆ go to Electron Transport Chain Honors Biology  Energy accounting of Krebs cycle 4 NAD + 1 FAD 4 NADH + 1 FADH2 pyruvate → → → → → → → → → 2x CO2 3 1 3x C A C 1 ADP 1 ATP TP Net gain = 2 ATP = 8 NADH + 2 FADH2 Honors 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 Honors Biology  Cellular Respiration Stage 4: Electron Transport Chain Honors 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! A working muscle recycles over Honors Biology 10 million ATPs per second  There is a better way! ▪ Electron Transport Chain ◆ series of molecules 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 ~34 ATP from 1 glucose! ◆ only in presence of O2 (aerobic respiration) O2 Honors Biology  Mitochondria ▪ Double membrane ◆ outer membrane ◆ inner membrane ▪ highly folded cristae ▪ enzymes & transport proteins ◆ intermembrane space ▪ fluid-filled space between membranes Honors Biology  Electron Transport Chain Inner mitochondrial Intermembrane space membrane C Q NADH cytochrome cytochrome c dehydrogenase bc complex oxidase complex Mitochondrial matrix Honors Biology  Electron Transport Chain NADH → NAD+ + H Building proton gradient! e intermembran e p space H H H + + + inner mitochondria H → e- + H+ C l membrane e Q – e e – H – FADH2 FAD H 1 NADH 2H+ + 2 O H2 NAD NADH+ cytochrome cytochrome 2 Oc dehydrogenase bc complex oxidase complex mitochondria l matrix Honors Biology What powers the proton (H+) pumps?…  Stripping H from Electron Carriers ▪ NADH passes electrons 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) ◆ transport proteins in membrane pump H+ (protons) across inner membrane to intermembrane space H+ + H H H H+ H+ H + + + + H+ H+ H H+ C e Q – e e – – FADH2 FAD AD NADH NAD + 1 O 2H + 2 P NADH+ H2cO A dehydrogenas cytochrome 2 cytochrome + Pi e bc complex oxidase complex T Honors Biology P H+  Electrons flow downhill ▪ Electrons move in steps from carrier to carrier downhill to O2 ◆ each carrier more electronegative ◆ controlled oxidation ◆ controlled release of energy Honors Biology  “proton-motive” force We did it! H + H H H ▪ Set up a H + + + + H H H H + + + + gradient ▪ Allow the protons to flow through ATP synthase ▪ Synthesizes ATP ADP + Pi → ATP ADP + Pi AT P H Honors Biology +  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 Honors Biology  Pyruvate from Intermembrane Inner H+ cytoplasm H+ space mitochondria l Electron membrane transport C system Q NADH e- 2. Electrons H+ provide energy 1. Electrons are harvested to pump protons Acetyl-CoA and carried to the transport e- system. across the - membrane. NADH e H2O - Krebs e 3. Oxygen joins 1 O FADH2 with protons to cycle 2 +2 O2 form water. 2H+ CO2 H+ 2 ATP H+ 3 ATP 4. Protons diffuse back in2 down their concentration ATP Mitochondrial gradient, driving the synthase matrix Honors Biology synthesis of ATP.  ~4 Cellular respiration AT 0 P 2 ATP + ~2 ATP + 2 ATP + ~34 ATP Honors Biology  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? Honors Biology  Any Questions? Honors Biology