2 Cellular Respiration There are two pathways for cellular respiration. Anaerobic Pathway-glycolysis and fermentationAerobic pathway-glycolysis paired with aerobic respiration in the mitochondria.Carbohydrates produced in photosynthesis are converted into the energy of the cell, ATP.Overall Equation:C6H12O6 + 6O CO2 + 6H2O + energy (ATP)
3 Respiration is a Redox Reaction Oxidation-reductionLEO the lion says GEROxidation is e- lossReduction is e- gainReducing agent is the e- donorOxidizing agent is the e- acceptor
4 Oxidizing Agent in Respiration NAD+(nicotinamide adenine dinucleotide)NAD+ is reduced to NADHEnzyme action: dehydrogenaseOxygen is the eventual e- acceptor
5 NAD+Only a small amount of NAD+ is needed in cells; each NAD+ is used over and over.Electrons received by NAD+ are high-energy electrons and are usually carried to the electron transport system.
6 FAD FAD coenzyme of oxidation-reduction can replace NAD+. FAD accepts two electrons and becomes FADH2.
7 How Cells Acquire ATP Glucose is high-energy CO2 & H2O are low-energy Process is exergonic andreleases energy.Glucose is oxidized andO2 is reduced.Buildup of ATP is an endergonic rxnthat requires energy.Breakdown of glucose yieldssynthesis of 36 or 38 ATP,preserving 39% of energy in glucose.
8 Cellular RespirationGlycolysis: occurs in cytosol; degrades glucose into pyruvateKreb’s Cycle: occurs in the mitochondrial matrix; converts pyruvate into carbon dioxideElectron Transport Chain: inner membrane of mitochondrion; electrons are passed to oxygen
9 Order of Events and how it leads into Aerobic Respiration. * First we will look at Glycolysisand how it leads into Aerobic Respiration.* Second we will look at our other pathway of Glycolysis into Fermentation.
10 Glycolysis Glycolysis is the breakdown of glucose to two pyruvate. Enough energy is released for immediate buildup of two ATP.Two NADH are also produced.Glycolysis takes place outside the mitochondria and does not utilize oxygen (anaerobic).
13 GlycolysisGlucose (C6) splits into two C3 molecules each with a phosphate group.4 total ATP are produced but two are used to phosphorylate glucose so there is a net gain of 2 ATP.The C3 molecules, pyruvate, enter the mitochondria if O2 is available to continue with aerobic respiration.If no O2 is available, glycolysis becomes part of fermentation.Let’s look at an aerobic environment first…
14 Inside The Mitochondria Glucose breakdown involves the transition rxn, the Krebs cycle, and the electron transport system.A mitochondrion has a double membrane with an intermembrane space between the outer and inner membrane.
16 Inside the Mitochondria Outer MembraneIntermembrane spaceInner MembraneCristaeFolds of inner membrane.Increases surface area for chemiosmosisETS occurs hereMatrixJelly-like substanceTransition Reaction and Kreb’s Cycle occur here.
18 Transition ReactionThe Transition Reaction links Glycolysis and the Krebs cycle.Pyruvate is oxidized to an acetyl group attached to co-enzyme A and CO2 is removed.This happenstwice for eachglucose molecule.
19 The Krebs CycleThe Krebs cycle is a series of reactions that give off CO2 and producing ATP.It occurs in the matrix of the mitochondria.The Krebs cycle produces two immediate ATP molecules per glucose molecule.6 NADH and 2 FADH2 are also formed and carry electrons to the ETS.CO2 is released- we exhale it.
21 The Electron Transport System Electron transport system is located in cristae of mitochondria.Consists of carriers that pass electrons.Electrons pass from higher to lower energy states, energy is released and stored for ATP production.Electrons that enter the electron transport system are carried by NADH and FADH2NADH gives up electrons, becoming NAD+System accounts for 32 to 34 ATP depending on the cell.
22 The Electron Transport System At each sequential oxidation-reduction rxn, energy is released to form ATP.O2 serves as a terminal electron acceptor and combines with hydrogen to form water.Because O2 must be present for system to work, it is called oxidative phosphorylation.
23 The Electron Transport System At each sequential oxidation-reduction rxn, energy is released to form ATP.O2 serves as a terminal electron acceptor and combines with hydrogen to form water.Because O2 must be present for system to work, it is called oxidative phosphorylation.
24 Cristae of Mitochondria NADH dehydrogenase complex, cytochrome b-c complex, and cytochrome oxidase complex all pump H+ ions into the intermembrane space.Energy released from flow of electrons down electron transport chain is used to pump H+ ions, carried by NADH and FADH2, into intermembrane space.
25 ATP Production in the Mitochondria ATP synthase complexes are channel proteins that also serve as enzymes for ATP synthesis.As H+ ions flow from high to low concentration, ATP synthase synthesizes ATP (Chemiosmosis).Once formed, ATP molecules diffuse out of the mitochondrial matrix through channel proteins.
26 Energy Yield From Glucose Breakdown SourceFADH2NADHATPGlycolysis2 ATP2 NADH4-6 ATPTransition6 ATPKreb’s6 NADH18 ATP2 FADH24 ATPTOTAL:36-38 ATP
28 Anaerobic PathwayIf O2 is not available to the cell, fermentation, an anaerobic process, occurs.During fermentation, glucose is incompletely metabolized to lactate or CO2 and alcohol.Fermentation results in a net gain of only 2 ATP per glucose molecule.
29 FermentationFermentation consists of glycolysis plus reduction of pyruvate to either lactate or alcohol and CO2.NADH passes its electrons to pyruvate instead of to an electron transport system.NAD+ is then free to return and pick up more electrons during earlier rxns of glycolysis.
30 Fermentation Examples Anaerobic bacteria produce lactic acid when we manufacture some cheeses.Anaerobic bacteria produce industrial chemicals: isopropanol, butyric acid, etc.Yeasts use CO2 to make bread rise and produce ethyl alcohol in wine-making.Animals produce pyruvate to lactate when it is produced faster than it can be oxidized by Krebs cycle.
31 Advantages and Disadvantages of Fermentation Fermentation provides quick bursts of ATP energy for muscular activity.Disadvantage is that lactate is toxic to cells.When blood can’t remove lactate from muscles, lactate changes pH and causes muscles to fatigue.Individual is in oxygen debt b/c oxygen is still needed after exercising.Recovery occurs after lactate goes to liver.
32 Efficiency of Fermentation Two ATP produced per glucose molecule during fermentation .Fermentation is much less efficient than complete breakdown of glucose in oxidative phosphorylation..