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CELLULAR RESPIRATION

CELLULAR RESPIRATION. How do cells harvest and access chemical energy ?. How is energy released from food?. Food molecules are slowly metabolized through various pathways to generate units of ATP

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CELLULAR RESPIRATION

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  1. CELLULAR RESPIRATION How do cells harvest and access chemical energy?

  2. How is energy released from food? • Food molecules are slowly metabolized through various pathways to generate units of ATP • These pathways take place in the cytoplasm (glycolysis) and mitochondria (Kreb’s Citric Acid Cycle and ETS)

  3. Cellular Respiration Equation C6H12O6 + 6O2 6CO2 + 6H2O + 36ATP

  4. How do cells “tap” energy? • Energy is contained in electron arrangement in the chemical bonds of organic fuels (e.g. glucose) • Cellular respiration basically shuttles electrons through a series of reactions and releases energy in form of ATP

  5. How much ATP does a human muscle cell need? 10 million molecules of ATP per second!!

  6. Aerobically Needs oxygen In slow-twitch muscle fibers Anaerobically Does notneed oxygen In fast-twitch muscle fibers Two basic ways to break down sugar to make ATP

  7. Connection between breathing and cellular respiration

  8. Oxygen Need • Breathing brings in oxygen from outside the body to our lungs (gas exchange) • Blood carries oxygen to our cells to carry out cellular respiration • Carbon dioxide is removed from cells and exhaled through lungs (gas exchange)

  9. Cellular Respiration Overview http://fig.cox.miami.edu/~cmallery/150/metab/c9x6cell-respiration.jpg

  10. 3 Stages of cellular respiration • 1. Glycolysis (in cytoplasm) • 2. Citric acid cycle (in mitochondrial matrix) • 3. Oxidative phosphorylation – Electron transport chain and chemiosmosis (on inner mitochondrial membrane)

  11. Glucose is oxidized to form carbon dioxide Produces CO2; Uses O2ATP and other energy molecules power cell respirationKrebs Citric Acid Cycle = Matrix of Mitochondria 3 Reactions Glycolysis = cytoplasm Kreb’s Citric Acid Cycle = matrix mitochondria ETS = Inner membrane cristae

  12. Glycolysis = substrate level phosphorylation 2 ATP Pay  Glycolysis  4 ATP Net Gain 2 ATP 2C3H6O3 or 2 pyruvate 2 NADH

  13. 2 pyruvate Mitochondria Outer membrane Acetyl COA CO2 Kreb’s CitricAcid Cycle 2NADH 6NADH 2 ATP Substrate level phosphorylation 2FADH2

  14. Electron Transfer e- ATP Oxidative Phosphorylation ATP Proteins In Membrane Oxygen H2O

  15. Animations Glycolysis Glycolysis GlycolysisGlycolysis Citric Acid Cycle Citric Acid CycleFatty Acid OxidativePhosphorylationETSOxidative PhosphorylationOxidativePhosphorylationATP Synthase Chemiosmosis

  16. Sprinting requires quick bursts of energy and intense action Long distance running requires endurance and slow, steady action Sprinter vs. marathon runner • Have more “fast-twitch” muscle fibers which contract quickly and powerfully • Good for short bursts of intense activity • Have more “slow-twitch” muscle fibers (80% in quadriceps) which contract slowly and continuously • Don’t tire as quickly

  17. Connection between photosynthesis and cellular respiration

  18. Loss H atoms C6H12O6 + 6O2 6CO2 + 6H2O + 36ATP Gain H atoms

  19. Oxidation: loss of electrons from a molecule “LEO the lion says Loss of Electrons is Oxidation Reduction: gain of electrons from a molecule GER!” Gain of Electrons is Reduction Oxidation-Reduction Reaction

  20. Redox reactions Oxidation + 2H H O H O Dehydrogenase Reduction NAD+ + 2H  NADH + H+ 2H+ + 2e-- Carries 2 e--

  21. Redox reactions • Oxidation and reduction reactions are always coupled together • One molecule loses electron(s) to the other molecule • Energy is released when electrons are passed from molecule to molecule in a cascade (electron transport chain)

  22. Redox Reactions • Oxidation reactions are exergonic • Reduction reactions are endergonic • Breaking down glucose involves a series of redox reactions with the help of a dehydrogenase enzyme and its coenzyme NAD+

  23. NAD+is a hydrogen carrier • A coenzyme molecule made from niacin (a B vitamin) • Shuttles electrons in redox reactions • Removes hydrogen atoms (with their electrons) from molecules (i.e. they become oxidized) • NAD+ then becomes reduced to NADH

  24. Electron carriers • NADH delivers electrons to a series of electron carriers in a cascade • In this cascade, electrons “fall” down an energy “hill” and release energy for making ATP along the way • Oxygen is at the bottom of the “hill” and is the final electron acceptor

  25. Glycolysis (rxn 1: cytosol) • “Sugar-splitting” • One glucose molecule is split into two pyruvic acid molecules through 9 steps • Reactants: glucose, ADP, phosphate, NAD+ and ATP • Net yield (Products): 2 ATP molecules, 2 NADH and 2 pyruvic acids

  26. 2 NAD+ 2 NADH 2H+ + Glucose 2 pyruvate 2ATP 2P 2ADP +

  27. Substrate-Level Phosphorylation Enzyme P ATP Adenosine P P ADP P Organic Substrate P

  28. “Bridge” Reaction: Pyruvic Acid is converted to Acetyl CoA NAD+ NADH H+ + 2 CoA pyruvate Acetyl CoA 1 3 CO2 Coenzyme A

  29. Citric Acid Cycle (Rxn 2: Matrix) • Acetyl CoA molecule is broken down into 2 carbon dioxides (CO2) • Reactants: Acetyl CoA, ADP, phosphate, NAD+, FAD and oxaloacetic acid • Net yield: Two ATP, six NADH, two CO2and two FADH2 molecules • Oxygen must be available (needs aerobic conditions)

  30. http://www.emc.maricopa.edu/faculty/farabee/BIOBK/enyld2.gif

  31. Oxidative phosphorylation (Rxn 3 Cristae) • A series of protein complexes in a row that become alternately oxidized and reduced, as electrons from NADH and FADH2 molecules pass through • Hydrogen ions actively transported to intermembrane space and result in 34 ATP molecules being produced

  32. Oxidative Phosphorylation http://www.chemistry.wustl.edu/~courses/genchem/LabTutorials/Cytochromes/images/Proteins.jpg

  33. Inhibitors http://www.steve.gb.com/images/science/respiratory_chain_inhibitors.png

  34. ATP yield from Cellular Respiration KrebsCitric AcidCycleSubstrate Level Phosphorylation2 ATP Glycolysis Substrate Level Phosphorylation2 ATP ETSChemiosmosisOxidative Phosphorylation ~ 34 ATP

  35. The energy in glucose • is released by many exergonic reactions a little bit at a time • is used to make ATP molecules by endergonic reactions

  36. Aerobic cellular respiration • Requires oxygen • Complete breakdown of glucose into CO2 • Involves citric acid cycle and oxidative phosphorylation

  37. Anaerobic Respiration • No oxygen required • Involves the conversion of glucose to pyruvic acid • Alcoholic fermentation: conversion of pyruvic acid to alcohol • Lactic acid fermentation: conversion of pyruvic acid to lactic acid

  38. Fermentation http://fig.cox.miami.edu/~cmallery/255/255atp/mcb8.5.fermentation.jpg

  39. Lactic acid fermentation Making yogurt and cheese from lactose sugar in milk by using anaerobic bacteria • Overexertion of human muscles from • strenuous exercise results in • lactic acid buildup • sore muscle “burn” • ATP and oxygen • supplies depleted

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