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Overview cellular respiration

Overview cellular respiration. Catabolic Pathways. Recall this is breaking down of complex molecules 2 types of pathways: Fermentation – partial pathway requires no oxygen Cellular respiration – oxygen is consumes. Anaerobic fermentation in yeast. Anaerobic fermentation humans.

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Overview cellular respiration

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  1. Overview cellular respiration

  2. Catabolic Pathways • Recall this is breaking down of complex molecules • 2 types of pathways: • Fermentation – partial pathway requires no oxygen • Cellular respiration – oxygen is consumes

  3. Anaerobic fermentation in yeast

  4. Anaerobic fermentation humans

  5. Cellular respiration is aerobic

  6. Cellular Respiration • Cellular respiration is the process of oxidizing food molecules, like glucose, to carbon dioxide and water. • The energy released is trapped in the form of ATP for use by all the energy-consuming activities of the cell.

  7. Remembering ATP • hydrolysis of the terminal phosphate of ATP yields between 11 and 13 kcal/mole of usable energy, depending on the intracellular conditions.

  8. NAD+ and FAD • 1. Each metabolic reaction in cellular respiration is catalyzed by its own enzyme.  2. As a metabolite is oxidized, NAD+ accepts two electrons and a hydrogen ion (H+); results in NADH + H+. 3. Electrons received by NAD+ and FAD are high-energy electrons and are usually carried to the electron transport system.

  9. FAD and NAD

  10. Respiration has four distinct stages: • 1. Glycolysis • 2. Krebs cycle • 3. Electron transport chain • 4. Oxidative phosphorylation

  11. Glycolysis • Glycolysis is the anaerobiccatabolism of glucose. • It occurs in virtually all cells. • In eukaryotes, it occurs in the cytosol. • C6H12O6 + 2NAD+ -> 2C3H4O3 + 2NADH + 2H+

  12. Glycolysis is enzyme driven • Shockwave – observe the step by step process as you look at your book as well as the animation. http://instruct1.cit.cornell.edu/courses/biomi290/ASM/glycolysis.dcr • Glycolysis • glycolysis

  13. Summary of yield • The net yield from each glucose molecule is 2 NADH, 2ATP and 2 molecules of pyruvate • An initial investment of 2 ATP yields 4 ATP and 2 NADH or a net gain of 2 ATP and 2 NADH

  14. Energy from glycolysis

  15. If molecular oxygen is present the pyruvate enters the mitochondria

  16. Mitochondria • Mitochondria are membrane-enclosed organelles distributed through the cytosol of most eukaryotic cells. • Their main function is the conversion of the potential energy of food molecules into ATP.

  17. Mitochondria have: • an outer membrane that encloses the entire structure • an inner membrane that encloses a fluid-filled matrix • between the two is the intermembrane space • the inner membrane is elaborately folded with shelflike cristae projecting into the matrix. • a small number (some 5–10) circular molecules of DNA

  18. Prior to entering the Krebs Cycle, pyruvate must be converted into acetyl CoA . • This is achieved by removing a CO2 molecule from pyruvate and then removing an electron to reduce an NAD+ into NADH. • An enzyme called coenzyme A is combined with the remaining acetyl to make acetyl CoA which is then fed into the Krebs Cycle. The steps in the Krebs Cycle are summarized below:

  19. Transition of pyruvate to acetyl CoA

  20. We are now back at the beginning of the Krebs Cycle. Because glycolysis produces two pyruvate molecules from one glucose, each glucose is processes through the kreb cycle twice. • For each molecule of glucose, six NADH2+, two FADH2, and two ATP.

  21. To review • Krebstca

  22. Points to remember • Each NADH made in the mitochondria yields 3 ATP • NADH made in outside mitochondria yields 2 ATP • FADH yields 2 ATP • You will need this information as we discuss the electron transport chain.

  23. Electron transport chain overview • Krebstca (if can’t open go to bio home page at the bottom of page )

  24. Harvesting the nrg • So far we have from glycolysis and the Kreb’s cycle: (per molecule of glucose) ATP by substrate phosphorylation NADH and FADH2 – (which account for most of the nrg stored from the metabolism of glucose )

  25. Electron Transport Chain • A collection of molecules found in the inner mitochondrial membrane

  26. Key points • Protons are translocated across the membrane, from the matrix to the intermembrane space • Electrons are transported along the membrane, through a series of protein carriers • Oxygen is the terminal electron acceptor, combining with electrons and H+ ions to produce water • As NADH delivers more H+ and electrons into the ETS, the proton gradient increases, with H+ building up outside the inner mitochondrial membrane, and OH- inside the membrane.

  27. http://www.wiley.com/legacy/college/boyer/0470003790/animations/electron_transport/electron_transport.swfhttp://www.wiley.com/legacy/college/boyer/0470003790/animations/electron_transport/electron_transport.swf • (follow electron transport ) • respiration info (go to electron transport chain) • Animations (should be mcgraw hill)

  28. Key Points to remember • 1. NADH and FADH2 donate electrons to the series of electron carriers in the ETC • The final electron acceptor is Oxygen creating water as a by product of cell resp.

  29. Points cont. • Electron transport is coupled to ATP by chemiosmosis. • Animation of Chemiosmosis during Aerobic Respiration

  30. Points cont. • At certain steps along the chain, electron transfer causes electron carrying protein complexes to move Hydrogen ions from the matrix to the intermembrane space storing energy as a proton-motive force (hydrogen gradient) • Animation of Chemiosmosis Proton Pumping

  31. Points continued • As hydrogen diffuses back into the matrix through ATP synthase, its exergonic passage drives the endergonic phosphorylation of ADP • Electron transport system: (follow NADH and FADH2 as well as counting number of ATP made.)

  32. Related Metabolic Pathways • Without oxygen electronegetive oxygen to pull the electrons down the transport chain, oxidative phosphorylation ceases. • Fermentation provides another avenue for the synthesis of ATP.

  33. Fermentation • 1. The oxidizing agent of glycolysis is NAD+ , not oxygen. • But glycolysis generates 2 ATP by oxidative phosphorylation. • Fermentation regenerates ATP by transferring electrons are transferred to pyruvate.

  34. The miracle of fermentation

  35. Process of alcohol 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 reactions of glycolysis.

  36. Alcohol fermentation • pyruvate is first decarboxylated to yield a 2-carbon substance acetaldehyde. Acetaldehyde is then reduced as hydrogens are transferred from NADH to acetaldehyde to produce ethyl alcohol.

  37. lactic acid fermentation • pyruvate is used as the direct acceptor of the hydrogens removed from NADH. The end product is a molecule of lactic acid. Lactic acid [or lactate] is a common by-product of anaerobic respiration in muscle cells.

  38. Advantage of Fermentation • provides quick burst of ATP energy for muscular activity.

  39. Disadvantage of Ferm. • lactate is toxic to cells. lactate changes pH and causes muscles to fatigue. lactate is sent to liver, converted into pyruvate; then respired or converted into glucose. • Two ATP produced per glucose molecule during fermentation

  40. Go through this site and do review questions. • Cell Respiration: Introduction • General & Human Biology

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