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Energy Production in Cell Respiration: Processes and ATP Synthesis

Explore cellular respiration phases - Glycolysis, Krebs Cycle, Fermentation - and ATP production mechanisms like Oxidative Phosphorylation. Learn about redox reactions, NAD+ and FAD enzymes, and the role of Chemiosmosis in creating ATP. Delve into the intricacies of how organic molecules yield energy for cell functions.

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Energy Production in Cell Respiration: Processes and ATP Synthesis

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  1. Inroduction to Cellular Respiration • Open systems need energy from outside sources. • Living organisms are open systems • Photoautotrophs(plants) capture the suns energy and convert it to chemical energy in the form of organic molecules through anabolic reactions.

  2. Organic Molecules • Organic molecules are burned in the presence of O2. • Some of the chemical energy is used to make ATP which is utilized for cellular work. • For example, the oxidation of glucose (a catabolic reaction) provides the energy to produce ATP.

  3. Cellular Respiration • The the break down of glucose to CO2 and H2O • The energy released is trapped in the form of ATP for use in all energy consuming activities of the cell • This process occurs in two phases

  4. Glycolysis • The first phase is called glycolysis • Occurs in the cytoplasm • Is an anaerobic process • Involves the breakdown of glucose to pyruvic acid. • The intermediates are oxidized. • Two ATPs produced by substrate level phosphorylation

  5. Krebs Cycle • Occurs in the mitochondrial matrix • Intermediate step between glycolysis and Krebs cycle removes a carboxyl group from pyruvic acid to produce aceytl CoA. • Acetyl CoA then enters the Krebs cycle to be oxidized to CO2 and H2O. • The electrons transferred from the intermediates in the Krebs cycle go the the ETC to make most of the ATP in cellular rerspiration.

  6. Fermentation • Pyruvic acid will only be converted to acetyl CoA if oxygen is present. • I f there is no oxygen pyruvate does not enter the mitochondria. • Fermemtation occurs and pyruvate is either reduced to lactic acid or ethanol. • The function of fermentation is restore the oxidized form of NAD+.

  7. ATP • Energy yielded from hydrolysis of ATP is used to transfer phosphates from one molecule to another through enzymes. • The phosphorylated molecule does work for the cell. • ATP is replenished through cellular respiration.

  8. ATP Made in Two Ways • Oxidative Phosphorylation • Uses electron transport chain to create a proton gradient across the inner mitochondrial membrane. • SubstrateLevelPhosphorylation • Transfer of a phosphate group from an intermediate to ADP to make ATP

  9. Complexes function in cellular respiration • NADH Dehydrogenase pumps protons into the inner membrane space to create a gradient. • Succinate Dehydrogenase oxidizes succinate. • Cytochrome c redcutase transfers electrons to cytochrome c oxidase. • Cytochrome c oxidase transfers electrons to 1/2O2 to form H2O. • ATP Synthase phosphorylates ADP to ATP as protons diffuse back across the inner mitochondrial membrane

  10. Chemiosomosis • The coupling of the exorgonic flow of electrons from the oxidation of food to endergonic ATP production. • Proton gradient is created across the inner mitochondrial membrane • As protons diffuse back across the membrane ADP is phosphorylated to ATP

  11. Oxidative Phosphorylation a Closer Look • Highly electronegative O2 pulls e- down the ETC towards a lower energy state. • The e- are harvested from glycolysis and the Krebs cycle. • This exorgonic slide of e- is coupled to ATP synthesis • For each molecule of glucose oxidized to CO2 and H2O, 36-38 ATPs are made.

  12. REDOX REACTIONS • Oxidation-reduction reactions invovle the partial or complete transfer of e- from one reactant to another. • Oxidation is the complete or partial loss of e-. • Reduction is the partial or complete gain of e-

  13. Redox Reactions • Electron transfer requires both a donor and and an acceptor. • Not all redox reactions involve the complete transfer of e-, but instead , may change the degree of sharing.

  14. Respiration and redox Reactions • Valence e- of carbon and hydrogen lsoe potential energy as they shift toward electronegative oxygen. • Released energy is used to make ATP • Organic molecules rich in carbon-hydrogen bonds are excellent fuels. • A mole of glucose yields 686 Kcal when burned • In cellular respiration, glucose is graduallly oxidized in a series of enzyme controlled steps during glycolysis and the Krebs cycle.

  15. NAD+and FAD • Hydrogens stripped from glucose are not passed directly to oxygen. • They are first passed to NAD+ or FAD. • NAD+ and FAD act as odidizing agents trapping energy rich e- from food molecules. • These reactions are catalyzed by dehydrogenases. • XH2 + NAD+ --------------X + NADH + H+ • Dehydrogenases take 2 hydrogen atoms molecule being oxidized. • Two e- and 1 proton are delivered to NAD+ to produce NADH. The extra proton is released into the sourounding solution.

  16. NAD+ and the ETC • NADH then drops off electrons to the ETC which regenerates NAD+. • FAD picks up 2 hydrogen atoms to become FADH2. • For every NADH that makes a trip to the ETC 3 ATP’s are made through chemiosomosis. • For every FADH2 that makes a trip to the ETC 2 ATP’s are made through chemiosomosis

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