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Chapter 9

Chapter 9. Cellular Respiration. I CAN ’ S/ YOU MUST KNOW. The difference between fermentation & cellular respiration The role of glycolysis in oxidizing glucose to two molecules of pyruvate

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Chapter 9

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  1. Chapter 9 Cellular Respiration

  2. I CAN’S/YOU MUST KNOW • The difference between fermentation & cellular respiration • The role of glycolysis in oxidizing glucose to two molecules of pyruvate • The process that brings pyruvate from the cytosol into the mitochondria & introduces it into the citric acid cycle • How the process of chemiosmosis utilizes the electrons from NADH & FADH2 to produce ATP

  3. 9.1 • Catabolic pathways release energy by oxidizing organic fuels • Occur when molecules are broken down • Releases the molecules’ energy

  4. 2 types of catabolism • 1) Fermentation • Partial degradation of sugars that occurs without O2 • 2) Cellular Respiration • Most prevalent & efficient catabolic pathway • Uses O2 as a reactant with the organic fuel • Known as AEROBIC RESPIRATION • CAN also use anaerobic respiration

  5. Carbs, Fats, & Proteins are all broken down in cellular respiration • Glucose is the primary nutrient molecule used: • C6H12O6 + 6O2 6CO2 + 6H2O + ENERGY (ATP/heat)

  6. The exergonic release of energy from glucose is used to phosphorylate ADP to ATP • Life processes constantly consume ATP • Cellular respiration burns the organic fuels & uses the energy to regenerate ATP

  7. Redox Reactions • Electrons are transferred from one reactant to another • Reduction = substance gains electrons & energy (reduced + charge) • Oxidation = substance loses electrons & energy (oxidized) • LEO GER

  8. The electron donor is called the reducing agent • The electron receptor is called the oxidizing agent • Some redox reactions do not transfer electrons but change the electron sharing in covalent bonds

  9. During cellular respiration, the fuel (such as glucose) is oxidized, and O2 is reduced:

  10. At key steps in cellular respiration: • Electrons are stripped from glucose • Each electron travels with a proton (forms hydrogen) • The hydrogen atoms are not transferred directly to oxygen (formula shows that) – they are passed to an electron carrier

  11. Electron Carrier: • Coenzyme NAD+ • NAD+ accepts 2 electrons + the stabilizing hydrogen ion to form NADH • NADH has been reduced & has gained energy • Stored energy used later to make ATP

  12. More than: C6H12O6 + 6O6 6CO2 + 6H2O + ENERGY • Cellular respiration has three stages: • Glycolysis (breaks down glucose into two molecules of pyruvate) • The citric acid cycle (completes the breakdown of glucose) • Oxidative phosphorylation (accounts for most of the ATP synthesis)

  13. 9.2Glycolysis • Occurs in cytosol • The degradation of glucose begins as it is broken down into two PYRUVATE molecules • The 6-Carbon glucose molecule is split into TWO 3-Carbon sugars through a long series of steps

  14. 2 major phases: • Energy (ATP) consuming phase • Energy (ATP) producing phase

  15. Energy consuming • 2 ATP are used • Destabilize glucose & makes it more reactive • Energy producing • Later in glycolysis, 4 ATP are made • Results in net gain of 2 ATP • 2 NADH are also made – used later

  16. NET gain of 2 ATP & 2 NADH • Most potential energy is still in the 2 pyruvates • Pyruvates will then move to step 2 – citric acid cycle

  17. 9.3Kreb’s (Citric Acid) Cycle • When O2 is present, pyruvates enter the mitochondria • Before Kreb’s begins, pyruvate is converted to acetyl CoA

  18. 1) Pyruvate uses a transport protein to move into the matrix of the mitochondria • 2) When there, an enzyme complex removes a CO2, strips away electrons to convert NAD+ to NADH, & adds coenzyme A to form acetyl CoA • 3) Two acetyl CoA’s are produced per glucose. It now enters the citric acid cycle

  19. Kreb’s (Citric Acid) • 8 steps – each catalyzed by a specific enzyme • The job of breaking down glucose is completed with CO2 released as waste • Each turn of the cycle requires the input of one acetyl CoA • Must make 2 turns before the glucose is completely oxidized

  20. One turn produces: • 2CO2, 3NADH, 1FADH2 & 1 ATP • Thus 2 turns produce: • 4CO2, 6NADH, 2FADH2 & 2 ATP

  21. At the end of the Kreb’s cycle all 6 carbons from glucose have been released as CO2 • Only 2 ATP have been produced • The rest is held in the electrons in the NADH & FADH2 • Utilized in the Electron Transport Chain

  22. 9.4ETC • The electron carriers will donate electrons to power ATP synthesis through OXIDATIVE PHOSPHORYLATION • In the cristae of the mitochondria • The ETC itself produces no ATP (comes from the products of the ETC)

  23. 4 Step Process of ETC • 1) ETC is embedded in the inner membrane of the mitochondria • Has 3 transmembrane proteins that act as hydrogen pumps • 2 carrier molecules that move electrons between hydrogen pumps

  24. 2) ETC is powered by electrons from NADH & FADH2 • As electrons flow, the loss of energy is used to pump protons across the inner membrane • At the end of the ETC, the electrons combine with 2 hydrogen ions & Oxygen to form water • Oxygen is the final electron acceptor – if none is available, the ETC STOPS!!!

  25. 3) Hydrogen ions flow down their gradient through ATP synthase (channel in protein) • ATP synthase harnesses proton motive force (the gradient of protons) to phosphorylate ADP • The proton motive force exists because inner mit. Membrane is impermeable to hydrogen ions

  26. 4) The movement of the proton motive force is called chemiosmosis • Energy-coupling mechanism that uses energy from the proton gradient to drive cellular work • The ETC & chemiosmosis compose OXIDATIVE PHOSPHORYLATION

  27. ATP yield per molecule of glucose is between 36 & 38 ATP • 32-34 comes from oxidative phosphorylation

  28. 9.5 • Fermentation allows a cell to produce ATP without Oxygen (anaerobic) • Consists of glycolysis (2 net ATP) & reactions that regenerate NAD+ • Oxygen not required to accept electrons

  29. Types of fermentation • 1) Alcohol • Pyruvate is converted to ethanol • Releases CO2 & oxidizing NADH to create more NAD+ • 2) Lactic acid • Pyruvate is reduced by NADH (NAD+) formed • Lactate is a waste product

  30. Facultative anaerobes • Organisms that make ATP by aerobic respiration if oxygen present • Can switch to fermentation in anaerobic conditions

  31. 9.6 • Proteins & fats are used to generate ATP through cellular respiration • Organic molecules are used in biosynthesis (the building of macromolecules) • Amino acids from the hydrolysis of proteins can be incorporated into the consumer’s own proteins

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