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Cellular Respiration Chapter 8 Cellular Respiration Chapter 8.

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Presentation on theme: "Cellular Respiration Chapter 8 Cellular Respiration Chapter 8."— Presentation transcript:

1 Cellular Respiration Chapter 8 Cellular Respiration Chapter 8

2 Cellular Respiration §There are two pathways for cellular respiration. §Anaerobic Pathway-glycolysis and fermentation §Aerobic pathway-glycolysis paired with aerobic respiration in the mitochondria. §Carbohydrates produced in photosynthesis are converted into the energy of the cell, ATP. §Overall Equation: l C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O + energy (ATP)

3 Respiration is a Redox Reaction Oxidation-reduction LEO the lion says GER Oxidation is e- loss Reduction is e- gain Reducing agent is the e- donor Oxidizing agent is the e- acceptor

4 Oxidizing Agent in Respiration §NAD + (nicotinamide adenine dinucleotide) §NAD + is reduced to NADH §Enzyme action: dehydrogenase §Oxygen 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 coenzyme of oxidation-reduction can replace NAD +. §FAD accepts two electrons and becomes FADH 2.

7 How Cells Acquire ATP §Glucose is high-energy §CO 2 & H 2 O are low-energy §Process is exergonic and releases energy. §Glucose is oxidized and O2 is reduced. §Buildup of ATP is an endergonic rxn that requires energy. §Breakdown of glucose yields synthesis of 36 or 38 ATP, preserving 39% of energy in glucose.

8 Cellular Respiration §Glycolysis: occurs in cytosol; degrades glucose into pyruvate §Krebs Cycle: occurs in the mitochondrial matrix; converts pyruvate into carbon dioxide §Electron Transport Chain: inner membrane of mitochondrion; electrons are passed to oxygen

9 Order of Events * First we will look at Glycolysis and 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).


12 ATP Production in Glycolysis

13 Glycolysis §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 O 2 is available to continue with aerobic respiration. §If no O 2 is available, glycolysis becomes part of fermentation. §Lets look at an aerobic environment first… Glucose (C6) splits into two C3 molecules each with a phosphate group.

14 §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. Inside The Mitochondria

15 Inside the Mitochondria

16 Outer MembraneInner Membrane Matrix Folds of inner membrane. Increases surface area for chemiosmosis ETS occurs here Cristae Jelly-like substance Transition Reaction and Krebs Cycle occur here. Intermembrane space

17 The Mitochondria

18 Transition Reaction §The Transition Reaction links Glycolysis and the Krebs cycle. § Pyruvate is oxidized to an acetyl group attached to co- enzyme A and CO 2 is removed. §This happens twice for each glucose molecule.

19 The Krebs Cycle §The Krebs cycle is a series of reactions that give off CO 2 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 FADH 2 are also formed and carry electrons to the ETS. §CO 2 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 FADH2 §NADH 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 SourceFADH2NADHATP Glycolysis2 ATP Glycolysis2 NADH4-6 ATP Transition2 NADH6 ATP Krebs2 ATP Krebs6 NADH18 ATP Krebs2 FADH24 ATP TOTAL:36-38 ATP


28 Anaerobic Pathway §If O2 is not available to the cell, fermentation, an anaerobic process, occurs. §During fermentation, glucose is incompletely metabolized to lactate or CO 2 and alcohol. §Fermentation results in a net gain of only 2 ATP per glucose molecule.

29 Fermentation §Fermentation 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 CO 2 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 cant 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..


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