Chapter 7: Deriving Energy From Food

1. Chapter 7:Deriving Energy From Food

2. Why do we need to breath? Oxygen allows us to extract energy from the food we consume. Energy ATP Muscle contraction Thinking Cell repair Requirements of Living

3. Recall: ATP 3 phosphates Powers a reaction by loosing the outermost phosphate ATP- 1PhosphateADP ADPATP requires energy ATP energy is extracted from the food we consume 7.1 Energizing ATP

4. Cellular respiration Down hill  high energy state to a lower energy state Down hill more stored less= Food being broken down to produce ATP Glucose energy is extracted Energy in the form of electrons The breakdown of glucose will run downhill Oxygen is needed as the final electron acceptor in the downhill When an ATP molecule is made an uphill reaction will occur 7.2 Electrons Fall Down The Energy Hill to Drive The Uphill Production of ATP

5. How electrons are transferred for endergonic reactions Recall: Some substances attract electrons more strongly then others do. Oxidation a substance that looses one or more electrons to another Reduction substance that gains electrons Electrons =negative charge the substance is reduced or less positive In cells both reactions occur as a combined operation known as a redox reaction The process by which electrons are transferrred from one molecule to another The Great Energy of Conveyers: Redox Reactions

6. Glucose is oxidized by another molecule, which is then oxidized by another molecule. The molecules that serve to transfer electrons from one molecule to the other in ATP formation are known as electron carriers The electrons being accepted by these molecules are mostly Hydrogen e- Many Molecules can Oxidize other Molecules

7. NAD nicotinamide adenine dinucleotide the most important electron carrier molecule It can exsists in two states Loaded NADH electron picked up When a hydrogen is added it becomes neutral NAD+(+H) NADH Once the Hydrogen atom is transferred to another molecule it returns to NAD+ Unloaded NAD+ (ionic form) electron dropped off Redox Through Intermediates: NAD

8. NAD+ oxidizes glucose derivatives This is made possible by enzymes NAD+ accepts the electrons and hands them off to another molecule This form of electron transfer provides for the highest production of ATP molecules. Diagram indicates the empty and loaded states of NAD+ How does NAD+ do its Job?

9. ATP Materials Glucose Redox Reactions Electron Carriers Enzymes The BIG PICTURE C6H12O6 + 6O2 + 36ADP + 36 P 6 CO2 +6H2O + 36ATP NOTE: 6 CO2 +6H2O are by-products 7.3 The Three Stages of Cellular Respiration: Glycolysis, The Krebs Cycle, and the Electron Transport Chain

10. Glycolysis 2 ATP Occurs at cytosol Krebs Cycle  2 ATP Occurs at mitochondria ETC  34 ATP Occurs at mitochondria Glycolysis and the Krebs Cycle Provides quick burst of Energy Transfers the electrons to electron carriers ETC Electron carriers are then oxidized to make ATP 1 molecule of Glucose = 36 ATP Cellular Respiration: Three main Phases

11. Glycolysis Yields 2 ATP from 1 Glucose molecules Small amounts of electrons First step of cellular respiration Evolved first Later ETC when oxygen was available ETC aerobic energy transfer Cellular respiration the aerobic harvesting of energy Glycolysis: First to Evolve, Less Efficient

12. Glycolysis “sugar splitting” Steps Glucose prepared for energy release Molecules of ATP are added to make two less-stable sugar molecules Each contains three carbons The proceeding steps occur to each molecule The sugar molecules become oxidized by NAD+NADH, they are transferred to the ETC The latter allows for the addition of phosphates to the sugar molecules The acids (sugar molecules) later loose their phosphate to ADPATP and become pyruvic acid Overall Glycolysis yields: 2 Molecules of ATP 2 Molecules of NADH 2 Molecules of Pyruvic acid 7.4 Fist Stage of Cellular Respiration: Glycolysis

13. Also known as the citric acid cycle the first product of the Krebs cycle Site of Action Moves from Cytosol to Mitochondria Two molecules of pyruvic acid make their way to the mitochondria The Krebs Cycle takes place in the interior of the inner membrane of the mitochondria The ETC takes place within the inner membrane 7.5 The second Stage of Respiration: Krebs Cycle

14. The two 3-carbon pyruvic acid molecules; Combines with coenzyme A Acetyl CoA Products Acetyl CoA enters the Krebs Cycle 1Carbon dioxide molecule Bloodstream One NADHETC Between Glycolysis and the Krebs Cycle, an Intermediate Step

15. Acetyl CoA + oxaloacetic acid= Citric acid At the end of the cycle oxaloacetic acid is once more produced Oxaloacetic acid is not only necessary as a substrate in the cycle but, it also serves as a product In the Krebs Cycle there is one new electron carrier FAD FADH2 Note: Figure 7.8 Occurs twice Two molecules of Acetyl CoA Krebs Cycle Yields 6 NADHETC 2FADH2ETC 2 ATP Into the Krebs Cycle: Why is it a Cycle?

16. ETC Site Mitochondrial inner membrane NADH and FADH2 that is produce is in Glycolysis and the Krebs cycle is transferred here They donate their electrons and Hydrogen ions to the ETC They are oxidized by enzymes in the ETC Carriers are reduced by receiving electrons When electrons are donated to the next carrier they become oxidized The carriers move through enzymes until the last electron acceptor is reached O2 7.6 The Third Stage of Respiration: The ETC

17. Note: The movement of electrons through the ETC releases enough energy to move H ions The H ions move from the inner membrane to the outer membrane Move from an area of low to high concentration (against their gradient) will make their way back in moving down their concentration gradient through the ATP synthase (enzyme) The energy the H ions produce on their way in powers the addition of a phosphate to ADP Where’s the ATP?

18. A single oxygen atom accepts two electrons+ two hydrogen atoms= H2O Finally, Oxygen is Reduced, Producing, Water

19. Bountiful Harvesting: ATP Accounting

21. When Energy Harvesting Ends at Glycolysis, Beer Can Be the Result Energy and Exercise