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Chapter 9

Cellular Respiration – Harvesting Chemical Energy. Chapter 9. Overview. Cellular Respiration is the process by which mitochondria break down glucose to make ATP C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O + Energy (ATP + heat) Catabolic Process ( exergonic ). Energy. Energy Released.

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Chapter 9

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  1. Cellular Respiration – Harvesting Chemical Energy Chapter 9

  2. Overview • Cellular Respiration is the process by which mitochondria break down glucose to make ATP • C6H12O6 + 6O2 6CO2 + 6H2O + Energy (ATP + heat) • Catabolic Process (exergonic)

  3. Energy • Energy Released • Cells are open systems • Require outside energy to perform cellular work

  4. ATP Review • ATP: nucleotide, high energy P bonds, drives endergonicrxns • ATP + H2O  ADP + Pi + Energy • Terminal phosphate gets enzymatically transferred to another compound • “Phosphorylates” the compound making it reactive • Phosphorylated compound can remove Pi to provide energy • Cell Respiration provides the energy required to regenerate ATP from ADP

  5. Phosphorylation • Substrate-Level • ATP produced • ADP + Pi = ATP • Direct transfer of Pifrom intermediate to ADP • Oxidative • ATP Produced • ADP + Pi= ATP • Exergonic transfer of electrons • Produces 90% of ATP

  6. becomes oxidized(loses electron) Xe- + Y X + Ye- becomes reduced(gains electron) Transfer of Electrons: REDOX rxns • Oxidation-Reduction (Redox) Reactions- chemical rxns that involve transfer of electrons • Oxidation: loss of electrons (more +) • Reduction: gain of electrons (more -) • As electrons move, they “carry energy” with them • Move as a part of a H atom

  7. becomes oxidized C6H12O6 + 6O2 6CO2 + 6H2O + Energy becomes reduced Putting into Cell Respiration… • Carbs and Fats are great energy stores because they have a lot of C-H bonds 

  8. NAD+ • H’s stripped from glucose are not transferred directly to O2 – passed to a special electron acceptor – NAD+ • Nicotinamide adenine dinucleotide • Functions as a coenzyme • Small nonprotein organic molecule that is required for certain enzymes to function • Assists enzymes in electron transfer during metabolism • Dehydrogenases– remove 2H and 2e- from substrate • Deliver 2e- and 1 H to NAD+  Becomes NADH • Other H is released to solution

  9. 2 e– + 2 H+ 2e–+ H+ H+ NADH NAD+ Dehydrogenase + 2[H] (from food) H+ + Nicotinamide (reduced form) Nicotinamide (oxidized form) LE 9-4

  10. NADH • Passes electrons down an electron transport chain • Series of steps instead of 1 big reaction • Oxygen pulls electrons down chain (due to electronegativity) • Yields energy to make ATP Oxidative Phosphorylation

  11. Cell Respiration – a Preview

  12. Glycolysis – “glyco” = sugar, “lysis” = split • Catabolic, 6-C glucose is split into two 3-C sugars which are then oxidized and rearranged into 2 Pyruvate molecules • Occurs with or without oxygen • Energy Investment Phase: • Cell uses ATP to phosphorylate intermediates • Energy Yielding Phase: • 2 ATPs per glucose are produced

  13. 2 ATPs USED MAKES AN ISOMER (FRUCTOSE)

  14. 4 ATP made NADH Substrate Level Phosphorylation

  15. Net 2 ATP

  16. We’re not done….  • IF Oxygen is present, pyruvate molecules enter the Mitochondria • Buttttttttt before it can do that, pyruvate has to be changed into a coenzyme called Acetyl CoA

  17. Krebs Cycle • Occurs in the mitochondrial matrix • Series of 8 enzyme-controlled steps • New electron “carrier” – FAD • Another coenzyme • Accepts 2e- and 2H to become FADH2 • New energy molecule – GTP (guanosinetriphosphate)

  18. Takes 2 turns to complete the oxidation of glucose

  19. Alright.. Where are we? • We have moved glucose from the cytosol into the mitochondria.. • We have made 2 ATP from glycolysis • And 2 ATP from the Krebs Cycle • These ATP have all been made by substrate level phosphorylation… not enough to keep you alive! • WE NEED OXIDATIVE PHOSPHORYLATION! • We have produced a lot of electron carriers.. NADH + FADH…. Let’s put them to work!!

  20. Electron Transport Chain • Occurs in the inner membrane of the mitochondria along cristae*only in the presence of O2* • A series of proteins are embedded in membrane • H pumps create concentration gradient • Yields ~34 ATP… that’s more like it..

  21. Animation ETC IN: 10 NADH 2 FADH2 ETC OUT: 32-34 ATP 6 H2O On average, 3 ATP are made per carrier

  22. OK, back to the beginning…. • C6H12O6 + 6O2 6CO2 + 6H2O + Energy 6 ETC AIR FOOD 2 ATP Glycolysis 2 ATP Krebs 32-34 ATP ETC 2 Krebs Prep 4 Krebs

  23. So… what happens if.. • You don’t have oxygen? • No ultimate electron acceptor • NADH and FADH2 cannot unload H’s • ATP production ceases • Cells run out of energy • You die.  • And just for fun: Cell Respiration Song

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