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Chapter 9 - Part 1: The Overview

Chapter 9 - Part 1: The Overview. Principles of Energy Harvest. Organic + oxygen  carbon + water + energy cmpds . dioxide C 6 H 12 O 6 + O 2  CO 2 + H 2 O + energy (ATP, heat).

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Chapter 9 - Part 1: The Overview

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  1. Chapter 9 - Part 1: The Overview

  2. Principles of Energy Harvest Organic + oxygen  carbon + water + energy cmpds. dioxide C6H12O6 + O2 CO2 + H2O + energy (ATP, heat)

  3. REDOX REACTIONS: involve electron transfers from 1 substance to another

  4. OXIDATION: loss of electrons (“energy releasing”) • REDUCTION: gain of electrons (“energy storing”)

  5. Example of Redox: Oxidation (loss of electrons) Na + Cl  Na+ + Cl- Reduction (gain of electrons)

  6. H+ • Glucose & other organic compounds are converted to usable energy by cells & by mitochondria • This occurs gradually, in a series of steps • There are key steps where H atoms are stripped from glucose or other substrate and passed to a coenzyme: NAD+ • (this is performed by an enzyme: dehydrogenase) NAD+ + 2H  NADH + H+

  7. NAD+ vs. NADH • Coenzyme found in 2 forms: • NAD+: oxidizing agent (gets reduced) • NADH: reducing agent (gets oxidized) • NAD+ is reduced to NADH by gaining 2 electrons and 2H (1 H immediately released) • NADH: “electron shuttle”

  8. CELLULAR RESPIRATION: • reactions in living cells in which sugars are broken down and energy is released Glucose + oxygen  carbon dioxide + water + energy C6H12O6 + 6O2 6CO2 + 6H2O + energy Mitochondria in a Liver Cell!!

  9. Cellular Respiration uses Redox reactions: oxidized C6H12O6 + 6O2 6CO2 + 6H2O+ ATP *the transfer of electrons from 1 element to another, more electronegative element (e.g. from H to O) releases stored potential energy  this chemical energy can be put to work! reduced

  10. • Food (glucose), like fuel, is “burned” by our cells for energy; • If it is burned all at once, too much energy is released. • So, the reaction is broken down into many small steps controlled by ENZYMES

  11. Example: Respiration uses an ELECTRON TRANSPORT CHAIN to break the fall of electrons into several energy-releasing steps (instead of one explosive reaction) e-

  12. ELECTRON TRANSPORT CHAIN: • Each step in the protein chain is more electronegative than the one before • Electron is “passed” from protein to the next using redox • oxygen captures those electrons at the “bottom” of the chain, and combines with aqueous H+ to form water.

  13. Reduction of oxygen!

  14. Ultimately, energy is transferred to the bonds of ATP which stores and releases the energy in usable amounts (packets) to be used by the cell

  15. Glucose = “large denomination” ($100) • ATP = “small change” ($1) *For each molecule of glucose, the cell can make approximately 36-38 ATP. 1 bond (≈ 7.3 kcal/mol) of energy is released when ATP is hydrolyzed

  16. 2 Modes of ATP Synthesis 1) oxidative phosphorylation: mode of ATP synthesis powered by redox reactions which transfer electrons from food  oxygen(occurs at the electron transport chain, or e.t.c.)

  17. 2) Substrate-level phosphorylation: • involves the transfer of inorganic phosphate from a molecule to ADP to form ATP. • mode of ATP synthesis occurring in: -glycolysis (2 ATP) -Krebs cycle (2ATP)

  18. Phase of Resp. Occurs where? Starts with? Ends with? # of ATP made Glycolysis cytoplasm Krebs cycle  inner matrix of mitochon.  2 pyruvate 4 CO2, NADH, FADH2 E.T.C. & oxidative phosphor. Main/Key Steps of Cellular Respiration: 1 glucose  2 pyruvate; NADH 2 2 cristae (inner memb. of mito. NADH, FADH2, O2 32-34 (approx.) H2O, ATP

  19. ETC (MEMBRANE) KREB’S (MATRIX) GLYCOLYSIS (cytosol)

  20. SUMMARY OF ELECTRON FLOW IN THE CELL: Food  NADH  E.T.C.  oxygen (glucose) *oxygen is the final electron acceptor!

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