Cell Respiration and Fermentation Lecture Notes PDF

Lecture Cell respiration and Fermentation Making cellular energy Lecture materials based on Pearson Education, Inc. resources Objectives page 1 Differentiate Heterotroph and autotroph th...

Lecture Cell respiration and Fermentation Making cellular energy Lecture materials based on Pearson Education, Inc. resources Objectives page 1 Differentiate Heterotroph and autotroph the chemical and energy relationships and exchanges between photosynthesis and cell Describe respiration What is a redox reaction? What is reduction? What is oxidation? How do these apply to cell Explain respiration? Although the ETC is part of the last steps of cell respiration it is the most important- why? What Explain does it use from the other steps of cell respiration in order to function? Describe What are the major steps of cell respiration? List What are the major ins and outs of each step of cell respiration For each major step of cell respiration name the major in’s and out’s and why they are important Describe (or waste) Where does each of the steps of cell respiration take place? Where appropriate relate the Identify structure of the mitochondria to the functions of these steps. Explain What is substrate level phosphorylation? How does it compare to oxidative phosphorylation? Define Aerobic respiration, anaerobic respiration and fermentation Explain If there is no oxygen how does that change the fate of the pyruvate? Why? Chemiosmosis, Proton Motive Force, ATP synthase, Electron transport chain, oxidative Define phosphorylation, electron acceptors Objectives page 1 What is the final electron acceptor in cell respiration? ( also- Think about Explain how this relates to the anatomical and physiological systems in the body? ) What is fermentation? How does it relate to glycolysis? What item is Explain regenerated in the fermentation process to keep glycolysis going? Between alcohol fermentation and lactic acid fermentation (both Compare similarities What are the and at least energy 3 major outputs differences) of the different steps of cell respiration, and how does fermentation output of ATP (through glycolysis alone) compare to Describe aerobic respiration? Why is fermentation important in our bodies and in our lives (outside of our Explain bodies) Why is it thought that glycolysis was the first among the steps of cell Explain respiration to arise in living things? Explain What other fuels can be used in cell respiration? How are fats broken down and where does each part enter the cell Identify respiration process Identify Where can amino acids enter the cell respiration process? Is cell respiration only for extracting energy? How does it relate to Explain ‘biosynthesis’ instead?  Life, work, energy Living cells require energy from outside sources to do work The work of the cell includes assembling polymers, membrane transport, moving, and reproducing O2+sunlight energy+ water → Cn(H2O)n+ O2 From photosynthesis in plants to make sugar…. To the use of those sugars to make ATP To the use of ATP to build complex organic molecules like proteins and fats! Cn(H2O)n+ O2 → CO2+ H2O  Animals can obtain energy to do this work Life, work, energy by feeding on other animals or photosynthetic organisms autotrophs (“self-feeders”) = Heterotrophs (other-feeders)= organisms that make all their organisms that consume organic own organic matter, from matter to obtain energy and inorganic compounds matter. Life, work, energy Energy flows into an ecosystem as sunlight and leaves as heat The chemical elements essential to life are recycled Life, work, energy Photosynthesis generates O2 and organic molecules, which are used in cellular respiration Cells use chemical energy stored in organic molecules to generate ATP, which powers work Catabolism Anabolism and Re-dox reactions Electron transfer plays a major role in these pathways These processes are central to cellular respiration Redox Rxns Chemical reactions that transfer electrons between reactants are called oxidation-reduction reactions, or redox reactions Redox= Reduction + Oxidation coupling Redox Rxns In oxidation, a substance loses electrons, or is oxidized In reduction, a substance gains electrons, or is reduced (the amount of positive charge is reduced) Redox electron donors The electron donor is called the reducing agent The electron receptor is called the oxidizing agent NAD+ ↔NADH as an Important electron carrier! As we talk about the process of cell respiration you are going to see NAD+ to NADH formation As an electron acceptor NAD+ functions as an oxidizing agent during cellular respiration NAD+ ↔NADH as an Important electron carrier! Each NADH (the reduced form of NAD+ ) represents stored energy that is tapped to synthesize ATP NADH is important as it transfers energy to the ETC (Electron Transport Chain) Check for understanding Look at the image to the right. Molecule _____ has B C been oxidized A: Isocitric acid Molecule _____ has been reduced, resulting in molecule _____ A D BC The electron transport chain in Cell respiration The ETC plays the role of setting up the PROTON MOTIVE FORCE (a concentration of H+ ions between the inner and outer membrane of the mitochondria This is where the energy to make the bulk of ATP in cell respiration comes from. Starting with the end in mind Electrons ripped off from the sugar Power pumping of H+ into the inter membrane space POWERFUL gradient (+, acidic, chemical) Drives ATP synthase Goal of ripping off electrons? 1) Pump the H+ 2) to make the gradient 3) Drives ATP synthase The “Three” stages of Cell respiration Harvesting of energy (according to your book) from glucose has three stages 1. G​ lycolysis (breaks down glucose into two molecules of pyruvate) 2. The citric acid cycle (completes the breakdown of glucose) 3. ​Oxidative phosphorylation (accounts for most of the ATP synthesis) Alternative way of separating out steps of Cell respiration: Although the book breaks it up into 3 stages (highlighted) , there are some inbetween and final stages worth mentioning The many chemical reactions that make up cellular respiration can be grouped into three main stage (and a half stage) and the final turnout 1. Glycolysis Split the sugar in 2 1.5 Pyruvic acid oxidation Convert Pyruvic Acid to A-CoA H Then tear all the e- ‘s and H+ ‘s 2. Citric acid cycle off 3. electron transport. Electrons used to pump H+ ions 4. Oxidative phosphorylationinto intermembrane space H+ gradient used to drive ATP synthesis (ADP+ P → ATP)  Cell respiration overview © 2017 Pearson Education, Inc.  Cell respiration overview © 2017 Pearson Education, Inc.  Cell respiration overview © 2017 Pearson Education, Inc. Self-Check for understanding Which of the following is NOT one of the major events in cell respiration (pick all that apply) A. Glycolysis B. The calvin cycle C. The krebs/Citric acid cycle D. Electron transport chain E. Glycosynthesis F. Hydrolysis G. ATP synthesis Preview For each molecule of glucose degraded to CO2 and water by respiration, the cell makes up to 32 molecules of ATP (this is mainly because of dumping the NADH and FADH2 into the ETC Alternative way of separating out steps of Cell respiration: Although the book breaks it up into 3 stages (highlighted) , there are some inbetween and final stages worth mentioning The many chemical reactions that make up cellular respiration can be grouped into three main stage (and a half stage) and the final turnout 1. Glycolysis Split the sugar in 2 1.5 Pyruvic acid oxidation Convert Pyruvic Acid to A-CoA H Then tear all the e- ‘s and H+ ‘s 2. Citric acid cycle off 3. electron transport. Electrons used to pump H+ ions 4. Oxidative phosphorylationinto intermembrane space H+ gradient used to drive ATP synthesis (ADP+ P → ATP)  Glyco =sugar Glycolysis Lysis=cutting a molecule of glucose is split into two molecules of a compound called pyruvic acid, usually located in the cytoplasm. glycolysis Copyright © 2016, 2013, 2010 Pearson Education, Inc. All Rights Reserved glycolysis Copyright © 2016, 2013, 2010 Pearson Education, Inc. All Rights Reserved glycolysis Copyright © 2016, 2013, 2010 Pearson Education, Inc. All Rights Reserved  Harvesting energy : ADP takes P from a substrate → ATP This is Substrate-Level phosphorylation Phosphorylation = Adding a phosphate To ADP, to make The phosphate to be transferred is being ripped Input: In: 2 P + 2NAD+ In: 2P + 4ADP+ 1 sugar 2 ATP Out: 4 ATP + 2 Pyruvate Input/ output of glycolysis Out: 2NADH =4 e- +2H+ → make that proton gradient! Copyright © 2016, 2013, 2010 Pearson Education, Inc. All Rights Reserved Recap Glycolysis input/output INPUT OUTPUT 1x sugar 2 pyruvate (3C-P) 2xATP 2xNAD+ (empty 2x NADH+ (carrying 2 carrier) electrons+ H+) 4 ADP 2x inorganic phosphates 4 ATP  What are the inputs and corresponding outputs? Purpose of each of these? Sugar provides the fuel source that 1 Sugar + 2 becomes the 2 pyruvate, the 2 ATPs are ATP in; initial energy investments to prime the 2 pyruvate out sugars 2NAD+ put in; NADH is carrying away electrons and an 2NADH out H+ to put into the electron transport chain Phosphates, which are used to make the 4 4ADP + 2 ATP (from the 2 phosphate originally inorganic P put invested and the inorganic ones). This is a in; 4 ATP out small payoff for investing the energy Check for understanding What are the major outputs of Glycolysis? From those outputs, can you tell me what the inputs had to be? Which of the following is NOT an output of glycolysis (select all that apply) A. NADH B. ATP C. Pyruvate D. FADH2 E. H2O Pause…. We are at a crossroad s There are 2 fates for the pyruvates Catabolism Anabolism and Re-dox reactions Aerobic respiration consumes organic molecules, O2 and yields ATP Anaerobic respiration is similar to aerobic respiration but consumes compounds other than O2 Fermentation is a type of anaerobic respiration and is a partial degradation of Catabolism Anabolism and Re-dox reactions Cellular respiration includes both aerobic and anaerobic respiration but is often used to refer to aerobic respiration Catabolism Anabolism and Re-dox reactions Although carbohydrates, fats, and proteins are all consumed as fuel, it is helpful to trace cellular respiration with the sugar glucose For now lets assume we have oxygen With this we can proceed through linkage reaction, citiric acid cycle and the ETC.  Step 2) Between glycolysis and citric acid cycle The pyruvic acid must be “groomed”—converted to a form the citric acid cycle can use. Called Pyruvate oxidation Priming pyruvate Acetyl-Co-A This step is carried out by a multienzyme complex that catalyzes three reactions 1. Oxidation of pyruvate and release of CO2 2. Reduction of NAD+ to NADH 3. Combination of the remaining two-carbon ETC sets up H+ fragment H+ and ion gradient To the ion gradient coenzyme used by ATP A to Synthase form acetyl CoA ETC Where does this take place? This is occurring as the fuel (pyruvate) is entering the mitochondria The end product (acetyl-Co- A) will wind up in the inner most part of the mitochondria (the Matrix) What you need to focus on That before you enter the Citric acid cycle the molecule must be groomed From pyruvate to Acetyl- co-A And the process generates another NADH (Pump those protons!)  What are the input’s and corresponding outputs of this linkage step? Purpose of each of these? Pyruvate cannot enter the krebs cycle, it 2 pyruvates put must be primed into A-CoA this is the in; 2 acetyl co- only form that can be further torn apart A out to make energy. 2NAD+ put in; NADH is carrying away electrons and an H+ to put into the electron transport 2NADH out chain 2CO2 Waste/by product that leaves the cell Check for understanding What other products are generated by this intermediate step to make Acetyl-COA (the only form that can enter the citric acid cycle)? A. H2O B. ATP C. NADH D. CO2  Step 2) Between glycolysis and citric acid cycle The pyruvic acid must be “groomed”—converted to a form the citric acid cycle can use. Called pyruvic acid oxidation Alternative way of separating out steps of Cell respiration: Although the book breaks it up into 3 stages (highlighted) , there are some inbetween and final stages worth mentioning The many chemical reactions that make up cellular respiration can be grouped into three main stage (and a half stage) and the final turnout 1. Glycolysis Split the sugar in 2 1.5 Pyruvic acid oxidation Convert Pyruvic Acid to A-CoA H Then tear all the e- ‘s and H+ ‘s 2. Citric acid cycle off 3. electron transport. Electrons used to pump H+ ions 4. Oxidative phosphorylation into intermembrane space H+ gradient used to drive ATP synthesis (ADP+ P → ATP) 3) Citric Acid Cycle The citric acid cycle finishes extracting the energy of sugar by dismantling the acetic acid molecules all the way down to CO2. x2 And we will get out per sugar: 2x 2CO2 = waste Pump 2x ATP 2x 3NADH those 2x FADH2 protons!  3) Citric acid cycle Acet Acetyl co-A yl- Joins a 4-C Co-A molecule Yields Citric acid Chemical processes regenerate the 4-C molecule and yield outputs  3) Citric acid cycle Acet Acetyl co-A yl- Co-A Joins a 4-C molecule We use our inputs To extract the energy from the remaining acetic acid Check for understanding Which of the following statements are true A. Glycolysis, formation of Acetyl-CoA from pyruvate, and citric acid cycle all make NADH B. Only Citric acid cycle produces FADH2. C. Only Glycolysis produces FADH2 D. FADH2 and NADH2 are waste, while CO2 carries electrons to the electron transport chain E. FADH2 and NADH deliver electrons to the Electron transport chain. Where is this taking place? This is occurring within the matrix (the inner most part of the mitochondria)  What are the input’s and corresponding outputs of the CAC? Purpose of each of these? 2 acetyl-co-A (2-C each) in Serving as the fuel to be torn apart Waste/by product that leaves the 4 CO2 cell 3NAD+ & 1FAD+ put NADH/FADH2 are carrying away in; electrons and an H+ to put into the 3NADH & 1 FADH2 out electron transport chain 2ADP + 2 inorganic - PO4 Small energy payoff 2 ATP out Check for understanding What is the main goal of glycolysis and Krebs cycle, in Aerobic (oxygen-using) cell respiration? A. To break the sugar and generate water B. To produce Massive amounts of ATP at these steps C. To provide high energy electrons for establishing an H+ gradient D. To break the sugar and produce CO2 Alternative way of separating out steps of Cell respiration: Although the book breaks it up into 3 stages (highlighted) , there are some inbetween and final stages worth mentioning The many chemical reactions that make up cellular respiration can be grouped into three main stage (and a half stage) and the final turnout 1. Glycolysis Split the sugar in 2 1.5 Pyruvic acid oxidation Convert Pyruvic Acid to A-CoA H Then tear all the e- ‘s and H+ ‘s 2. Citric acid cycle off 3. electron transport. Electrons used to pump H+ ions 4. Oxidative phosphorylation into intermembrane space H+ gradient used to drive ATP synthesis (ADP+ P → ATP) And now for the main event… 4) Electron Transport Chain! Remember ALL of those NADHs (2 electrons and a H+) and the FADH2s (2 electrons and 2 H+) Deliver their electrons to the INNER membrane of the mitochondria 4) Electron Transport Chain! These electrons from NADH and FADH2 are passed onto protein pumps which use the e- energy toto pump the H+ into the intermembrane space This Concentrates the H+ in that space Creating POWERFUL gradient (chemical, charge , pH)  Here is another illustration of the process (focus on the part within the shape) Electrons dropped off building up a gradient to make the ATP Lets briefly talk about how ATP is made from this energy How the electrons pass through the ETC Important! Note: The electron transport chain DOES NOT generate ATP directly It breaks the large free-energy drop from food to into smaller steps that release energy in manageable amounts The purpose of the ETC Each passing of electrons pumps H+ ions into the intermembrane space, creating potential energy in the form of a powerful electrochemical gradient A= cytoplasm, B= outer membrane of mitochondria, C= intermembrane space, D=inner membrane space of mitochondria, E= Matrix The ETC of the bacteria Chemiosmosis Electrons (from NADH) pass down the electron transport chain while protons are pumped across the membrane Establishes proton gradient PROTON MOTIVE FORCE!  Your mitochondria (and ATP Synthase! bacterial membranes) have structures that act like turbines. Each mini machine = ATP synthase, ENZYME embedded in the inner membrane for mitochondria; outer membrane for bacteria) near the electron transport chains ATP Synthase! 2nd method of Remember the making ATP PROTON MOTIVE FORCE! H s flow down their concentration + gradient (Super powerful gradient!) driving (literally turning the turbine) to force the following reaction: H+ ion gradient drives ATP synthase The H+ ions move into binding sites on the rotor of ATP Synthase This causes the protein to spin in a way that catalyzes phosphorylation of ADP to ATP This is an example of “chemiosmosis” ATP production from ADP + P Notice how an ADP and a phosphate bind AS the protein turns 120 ° it causes the catalytic head to squeeze Until the 3rd phosphate is forced onto the ADP to make ATP https://biologynotesonline.com/electron-transport-chain/  sds  This type of When making ATP via ATP synthase phosphorylation also has a special ADP + P  ATP name: The P is not taken off a substrate; Oxidative thus it is NOT substrate-level Phosphorylatio phosphorylation n Instead, we call this : Oxidative phosphorylation  Check for understanding What is the role of the electron transport chain proteins (what do they physically do)? These proteins in the ETC use electrons (delivered to the ETC by the NADH and the FADH2 ) to pump H+ ions across the inner mitochondrial membrane , and building up an H+ gradient in the intermembrane space Check for understanding (2 of 3) What is the special term we give to refer to this pumping of ions to create this PROTON MOTIVE FORCE ? Chemiosmosis Check for understanding What is the purpose of this established proton gradient, why does the cell (or mitochondria) go through so much trouble!? The gradient of H+ ions drives ATP synthase How does it achieve the desired goal/product? H+ ions flow down their concentration gradient back into the matrix they cause ATP synthase to turn which drives the P+ ADP → ATP reaction Other molecular fuels for making ATP We will come back to this concept later, But notice how everything leads to the ETC  ???? Where does the e- go? You need an atom that can accept electrons! Electro negative atoms! Here are the top 4 most electronegative (electron-loving) atom! LETS PLAY A DATING GAME ❷ ❶ F Cl ❸ N N O ❹ Oxygen will accept 2 electrons 2 electrons To balance out those negative charges though… it will also take two of those H+ ions. H H O H H + + What is this molecule? Oxygen is the final electron acceptor!!!!!! This is why oxygen is so vital to our lives In every cell oxygen atoms accept the electrons along with 2 of those H+ ions 2O2+ 4H+ + 4 e- → 2H2O neutral molecules Check for understanding What is the final electron acceptor when the electron exits the electron transport chain? A. Nitrogen B. Fluorine C. Oxygen D. Water E. Chlorine F. ATP  How much ATP? By using this method, the cell can make up to 32ATP for every glucose it takes apart. a lot better than glycolysis alone Importance of oxygen’s role in the ETC Most cellular respiration depends on electronegati ve oxygen to pull electrons down the transport chain Without oxygen, the electron transport chain will cease to operate  sds However….. Check for understanding After functioning anaerobically for about 15 seconds, muscle cells begin to generate ATP by the process of fermentation. Without O2 you cannot run the electron transport chain. Why is this? Answer A: O2 is the FINAL electron acceptor O2+ 4H+ + 4 e- → 2H2O molecules Without O2 the electrons in the ETC have no where to go, and the protein pumps cannot pump H+ s. ATP production without oxygen In the case of oxygen not being present…. Glycolysis can run & make ATP, but ONLY if coupled with…. anaerobic respiration or fermentation (fermentation is the more common of the two!) Anaerobic Cell Respiration In stagnant water the oxygen often is depleted due to Anaerobic respiration decomposition of decaying material you will often find uses an electron anaerobic bacteria (like purple sulfur bacteria in transport chain with these areas a final electron acceptor other than oxygen, for example, sulfate This is mostly true for various microorganisms (like purple sulfur bacteria) It is not typical of larger animals! This does NOT occur in humans Fermentation Fermentation uses substrate-level phosphorylation instead of an electron transport chain to generate ATP Fermentation consists of glycolysis plus reactions that regenerate NAD+ , which is required for glycolysis to run Fermentation Two common types are alcohol fermentation and lactic acid fermentation Note the differences between them (in their end products and number of steps!) The overall goal is the same. Lactic Acid fermentation (detailed) In lactic acid fermentation, pyruvate is reduced by NADH, forming NAD+, and lactate as end products, Note: there is no carbon dioxide released! The lactate is a 3- carbon structure like pyruvate Lactic Acid fermentation (simplified) In lactic acid fermentation, pyruvate is reduced by NADH, forming NAD+, and lactate as end products, Note: there is no carbon dioxide released! The lactate is a 3-carbon structure like pyruvate And lactic acid…HURTS! Lactic acid builds up in the muscles as a result of exercise in which not enough oxygen can get to all the hard-working muscle cells This is what causes that horrible painful ache in your muscles after a long work out But your body can get rid of it slowly over time. Alcohol Fermentation (detailed) In alcohol fermentation, pyruvate is converted to ethanol in two steps The first step releases CO2 from the pyruvate The second step generates NAD+ from NADH, and ethanol a) Alcohol fermentation (detailed) Lactic Acid fermentation (simplified) In alcohol fermentation, pyruvate is converted to ethanol in two steps The first step releases CO2 from the pyruvate The second step generates NAD+ from NADH, and ethanol  What are the input’s and corresponding outputs for fermentation? Purpose of each of these? 1sugar+ all stuff Glycolysis provides a net gain of 2ATP for for glycolysis in every glucose Pyruvate out The process remakes the NAD+ that can go 2NADH put in; back into glycolysis to keep it going to NAD+ out produce the net 2 ATP 2 pyruvate (3- C) in The pyruvate acts as the electron acceptor 2 Ethanol (2-C) when oxygen is not present; Ethanol is the out byproduct 2CO2 Waste/by product that leaves the cell  Be able to describe both Expectatio fermentation processes and identify n their differences (from the process and products) and the similarities  Yeast is capable of cellular respiration and fermentation and can perform alcoholic fermentation to produce CO2 and ethyl alcohol instead of lactic acid. For thousands of years, people have put yeast to work producing alcoholic beverages such as beer and wine. As every baker knows, the CO2 bubbles from fermenting yeast also cause bread dough to rise. Fermentation alone is enough to sustain many microorganisms. The lactic acid cheese, sour cream, produced by and yogurt fungi and soy sauce, pickles, bacteria using lactic acid cabbage, and olives, fermentation is and sausage meat used to produce products. Comparing Anaerobic ATP production processes For Anaerobic cell respiration, ethanol fermentation and Lactic acid fermentation… Another big difference is that… Cellular respiration Compared to (anoxygenic or fermentation which oxygenic) produces 30- only produces 32 ATP per glucose 2 ATP per glucose Obligates vs Facultatives Obligate anaerobes carry out fermentation or anaerobic respiration and cannot survive in the presence of O2 Obligates vs Facultatives Yeast and many bacteria are facultative anaerobes, meaning that they can survive using either fermentation or cellular respiration In a facultative anaerobe, pyruvate is a fork in the metabolic road that leads to two alternative catabolic routes The ancient way of Glycolysis Glycolysis is an older/more ancient process than the CAC and ETC Early prokaryotes likely used glycolysis to produce ATP before O2 accumulated in the atmosphere Glucose is not the only fuel! Respiration is a versatile metabolic furnace that can “burn” many other kinds of food molecules. Amino acids, fatty acids and glycerol's can all enter at various areas of the cycle. Fat Catabolism Fats are digested to glycerol (used to produce compounds needed for glycolysis) and fatty acids Fatty acids are broken down by beta oxidation and yield acetyl-CoA, NADH, and FADH2 And the glycerol enters partway through the glycolysis pathway Fat Catabolism An oxidized gram of fat produces more than twice as much ATP as an oxidized gram of carbohydrate Carbohydra Fats Proteins tes 1g= 9 1 g= 4 1g= 4 Calories calories calories Biosynthesis The body uses small molecules from food to build other their own molecules such as proteins These small molecules may come directly from food, from glycolysis, or from the citric acid cycle Coming up next Plants and Photosynthesis ! Supplementary Slides  Lets jump into Glycolysis! © 2017 Pearson Education, Inc. Glycolysis Glyco= sugar Lysis= cutting Glycolysis (“sugar splitting”) breaks down glucose into two molecules of pyruvate Glycolysis Glycolysis occurs in the cytoplasm and has two major phases Energy investment phase Energy payoff phase Glycolysis occurs whether or not O2 is present or not Glycolysis- Energy investment phase 1. For each glucose an ATP is invested, donating a phosphate group to produce G-6-P GLYCOLYSIS: Energy Investment Phase Glycolysis- Energy investment phase 2. G-6-P is rearranged into Fructose-6- phosphate ( an isomer) GLYCOLYSIS: Energy Investment Phase Glycolysis- Energy investment phase F-6-P then receives a 2nd ATP (now a total of 2ATP have been invested) This creates F-1-6-Bisphosphate GLYCOLYSIS: Energy Investment Phase Glycolysis- Energy investment phase F-1-6-BP is cleaved in half each half having a phosphate. One of these is G-3-P The other is DHAP Only the G-3-P form can go forward to an isomerase turns DHAP G-3-P GLYCOLYSIS: Energy Investment Phase Onto the Energy Harvesting Phase Now that we have invested some ATP and split the sugar into 2 parts…. And changed the DHAP to a G-3-P We can process the 2 G-3-P sugars and harvest some ATP! Glycolysis- G3P will progress towards energy harvest Reminder we now have G3P sugars only since any DHAP is converted to G3P (from our energy investment Glycolysis- Energy harvest phase So we start with the G3P sugar x 2 (so remember that we will go through this process 2 times for every glucose. Glycolysis- Energy harvest phase Now we are going steal some electrons! Those electrons will be taken to the ETC to make a gradient that ATPsynthase will use! H+ ion gradient To the ETC ETC sets up H+ used by ATP ion gradient Synthase Glycolysis- Energy harvest phase At this tsge we also add 2 inorganic phosphate groups. Priming the molecule in a way that will let us make 2 ATP for each G3P processed. H+ ion gradient To the ETC ETC sets up H+ used by ATP ion gradient Synthase Note! inorganic P added To each G3P Glycolysis- Energy harvest phase Remember we have two G-3-P sugars going through this so we generate 2NADH, and 2x 1,3-BP-G H+ ion gradient To the ETC ETC sets up H+ used by ATP ion gradient Synthase Glycolysis- Energy harvest phase The 1,3-BPG (2 of them) have a high energy phosphate that is taken off by an ADP in a substrate-level phosphorylation; generating 3-PG H+ ion gradient To the ETC ETC sets up H+ used by ATP ion gradient Synthase Note! inorganic P Pay off! We added use the P on To each the 1,3,-BPG G3P x2 Glycolysis- Energy harvest phase 3-P-G is rearranged into 2-P-G H+ ion gradient To the ETC ETC sets up H+ used by ATP ion gradient Synthase Note! inorganic P Pay off! We added use the P on To each the 1,3,-BPG G3P x2 Glycolysis- Energy harvest phase The 2-P-G is processed and 2Hs and an Oxygen are lost generating PEP H+ ion gradient To the ETC ETC sets up H+ used by ATP ion gradient Synthase Note! inorganic P Pay off! We added use the P on To each the 1,3,-BPG G3P x2 Glycolysis- Energy harvest phase The PEP contains another phosphate we can snag with an ADP to make another set of ATP via substrate-level phosphorylation H+ ion gradient To the ETC ETC sets up H+ used by ATP ion gradient Synthase Note! inorganic P Pay off! We added use the P on 2nd Pay off! To each the 1,3,-BPG We use the P G3P x2 on the PEP The final Product of Glycolysis : Pyruvate! 2 pyruvate are generated for each glucose Sometimes it is referred to as pyruvic acid as it has an acid form due to its carboxylic acid. Recap Glycolysis input/output INPUT OUTPUT 1x sugar 2 pyruvate (3C-P) 2xATP 2xNAD+ (empty 2x NADH+ (carrying 2 carrier) electrons+ H+) 4 ADP 2x inorganic phosphates 4 ATP The two paths Pyruvate can take…. In the presence of O2 pyruvate enters a mitochondrion (in eukaryotic cells), where the oxidation of glucose is completed If there is No oxygen the pyruvate will take another path in fermentation so that NAD+ can be regenerated so glycolysis can continue. The two paths Pyruvate can take…. Let’s assume that there is oxygen and follow the pyruvate into the mitochondria and onto the next phase of catabolic reactions to extract the remaining energy out of the pyruvate! But pyruvate cannot simply enter the next step, we have to prime it first! Priming pyruvate Acetyl-Co-A Before the citric acid cycle can begin, pyruvate must be converted to acetyl coenzyme A (acetyl CoA), which links glycolysis to the citric acid cycle Priming pyruvate Acetyl-Co-A This step is carried out by a multienzyme complex that catalyzes three reactions 1. Oxidation of pyruvate and release of CO2 2. Reduction of NAD+ to NADH 3. Combination of the remaining two-carbon ETC sets up H+ fragment H+ and ion gradient To the ion gradient coenzyme used by ATP A to Synthase form acetyl CoA ETC The Citric Acid Cycle The citric acid cycle, also called the Krebs cycle, completes the breakdown of pyruvate to CO2 ; generating FADH & NADH as electron carriers, and a bit of ATP The Citric Acid Cycle The cycle oxidizes organic fuel derived from pyruvate, generating : 1ATP x 2 cycles (one for each Acetyl-CoA) 3 NADH x 2 cycles 1FADH2 (another electron carrier) x2 cycles Reminder 1 glucose 2 pyruvates The 2 pyruvates 2 acetyl-CoA 2 actyl-CoA , each one goes through the CAC. Citric acid Cycle- Entry (pyruvate oxidation recap) Remember that pyruvate cannot enter directly to the CAC, so first it has to be changed into Acetyl co-A The Co-A is a co- enzyme needed for the first step of the CAC CAC overview Inputs and outputs Put in: Actyl CoA (2 per glucolse) 3 NAD+ (6 tot. per glucose) 1 ADP+ P (2 per glucose) FAD (2 per glucose) Output: 2 CO2 (total 4 per glucose) 6NADH (12 per glucose) ATP (2 per glucose) FADH (2 per glucose) CAC steps Actyle-Co-A binds with a starter molecule callec oxaloacetate The A-coA is a coenzyme that helps facilitate this process Citrate (a 6-C molecule) is the first product (and gives this cycle its name) CAC steps Citrate is rearranged into “isocitrate” (an isomer) The isocitrate has its hydrogens stripped off (electrons by NAD+ to NADH, and the H+ ions follow) This forms alpha- ketoglutarate CAC steps The a-ketoglutarate is Decarboxylated (looses a CO2) And an NAD+ takes away another set of electrons (and H+ ions follow) This forms succinyl –Co-A CAC steps Succinyl-CoA is processed into succinate and an ATP is made in the process Really GTP is formed (the same as ATP but with a guanine nitrogenous base instead of adenine) And then ADP is phosphorylated by the GTP. CAC steps The Succinate then is stripped of its electrons (by FAD, and the H+ ions are also taken by the FAD to make FADH2) This results in the formation of Fumarate CAC steps Fumarate is transformed to malate Malate is formed into oxaloacetate as NAD+ comes in and steals electrons (and H+ ions follow) Remember the NADH and FADH 2 are delivering electrons to the ETC! The purpose of the NADH and FADH2 Following glycolysis and the citric acid cycle, NADH and FADH2 account for most of the energy extracted from food! These two electron carriers donate electrons to the electron transport chain, which powers ATP synthesis via oxidative phosphorylation Electron Transport Chain (ETC) The electron transport chain is in the inner membrane (cristae) of the mitochondrion Most of the chain’s components are proteins, which exist in multiprotein complexes A= cytoplasm, B= outer membrane of mitochondria, C= intermembrane space, D=inner membrane space of mitochondria, E= Matrix  Electron carriers (and the proteins of Electron Transport Chain (ETC) the ETC) alternate between reduced and oxidized states as they accept and donate electrons How the electrons pass through the ETC Electrons are passed through a number of proteins including cytochromes (each with an iron atom) Electrons drop in free energy as they go down the chain Each step is a redox reaction…. And each pass through a protein will pump H+ ions Electron Transport Chain (ETC)- End of the line for the electrons Electrons drop in free energy as they go down the chain and are finally passed to the final electron carrier We will come back to the final electron carrier shortly. H+ ion gradient drives ATP synthase chemiosmosis, the use of energy in an H+ ion gradient to drive cellular work Electron Transport Chain (ETC)- End of the line for the electrons The final electron acceptor is essential to the function of the ETC If there is nothing to accept the electron at the end of the ride….then the whole system will shut down! But you need a VERY electronegative atom to accept those electrons… The ancient way of Glycolysis The support behind glycolysis being a more ancient (earlier) process to arise is supported by evidence such as: It is a process used in both cellular respiration and fermentation, it is the most widespread metabolic pathway on Earth Glycolysis occurs in the cytosol so does not require the membrane- bound organelles of eukaryotic cells Regulating ATP production Feedback inhibition is the most common mechanism for metabolic control If ATP concentration begins to drop, respiration speeds up; when there is plenty of ATP, respiration slows down Key enzymes in the metabolic pathway are regulated by feedback regulation.