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Cellular Respiration: Harvesting Chemical Energy in Cells

Explore the process of cellular respiration and how it provides energy for life. Learn about the different stages of cellular respiration and how energy is produced in the form of ATP.

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Cellular Respiration: Harvesting Chemical Energy in Cells

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  1. 0 Chapter 6 How Cells Harvest Chemical Energy

  2. 0 How Is a Marathoner Different from a Sprinter? Human muscles contain two different types of muscle fibers that perform differently under different conditions The ratio of types of fibers is determined genetically and cannot be converted from one type to another.

  3. 0 The different types of muscle fibers function either aerobically, with oxygen, or anaerobically, without oxygen. The slow muscle fibers are muscle cells that can sustain repeated, long contractions but don’t generate a lot of quick power for the body. Fast fibers are better able to produce ATP anaerobically Cellular respiration Is the process by which cells produce energy aerobically

  4. 0 INTRODUCTION TO CELLULAR RESPIRATION 6.1 Photosynthesis and cellular respiration provide energy for life In photosynthesis, which occurs in the chloroplast, the energy of sunlight is used to rearrange the atoms of CO2 and H2O to produce glucose and O2. In cellular respiration, which occurs in the mitochondria, O2 is consumed as glucose is broken down to CO2 and H2O. The CO2 and H2O released by cellular respiration are converted through photosynthesis to glucose and O2, which are then used in respiration.

  5. 0 Sunlight energy ECOSYSTEM Photosynthesis in chloroplasts The processes of photosynthesis and cellular respiration are complementary. During these energy conversions, some energy is lost in the form of heat. Photosynthesis uses solar energy to produce glucose and O2 from CO2 and H2O Glucose CO2   H2O O2 Cellular respiration in mitochondria ATP (for cellular work) Heat energy Figure 6.1

  6. 0 O2 Breathing CO2 6.2 Breathing supplies oxygen to our cells and removes carbon dioxide Breathing provides for the exchange of O2 and CO2 between an organism and its environment Respiration is gas exchange, and cellular respiration produces ATP. Lungs O2 CO2 Bloodstream Muscle cells carrying out Cellular Respiration Glucose  O2 CO2 H2O ATP Figure 6.2

  7. 0 6.3 Cellular respiration banks energy in ATP molecules Cellular respiration breaks down glucose molecules and banks their energy in ATP C6H12O6 O2 CO2 6 6 H2O ATPs + + 6 + Carbon dioxide Glucose Energy Oxygen gas Water Figure 6.3

  8. Cellular respiration: Consumes glucose. Produces water. Produces carbon dioxide. Releases heat. Is accomplished by many steps.

  9. 0 CONNECTION 6.4 The human body uses energy from ATP for all its activities ATP powers almost all cellular and body activities Table 6.4

  10. Humans use the calories they obtain from food as their source of energy. Humans use about 75% of their daily calories for involuntary life-sustaining activities such as digestion, circulation, and breathing.

  11. 0 6.5 Cells tap energy from electrons “falling” from organic fuels to oxygen During cellular respiration, the energy in glucose is carried by electrons. Electrons lose potential energy during their transfer from organic compounds to oxygen Oxidation is the loss of electrons, and reduction is the gain of electrons.

  12. 0 Loss of hydrogen atoms (oxidation) When glucose is converted to carbon dioxide it loses hydrogen atoms, which are added to oxygen, producing water C6H12O6 6 CO2 Energy 6 O2 + 6 H2O + + Glucose (ATP) Gain of hydrogen atoms (reduction) Figure 6.5A

  13. 0 Oxidation In biological systems, dehydrogenase is an important enzyme involved in the regulation of redox reactions. Dehydrogenase removes electrons (in hydrogen atoms) from fuel molecules (oxidation) and transfers them to NAD+ (reduction) H + O 2H H O Dehydrogenase Reduction H NAD+_ NADH + 2H + (carries 2 electrons) 2H+ 2e + Figure 6.5B

  14. 0 NADH ATP NAD NADH passes electrons to an electron transport chain As electrons “fall” from carrier to carrier and finally to O2 energy is released in small quantities  2e Controlled release of energy for synthesis of ATP H Electron transport chain 2e 1 O2 2 H 2 H2O Figure 6.5C

  15. 0 STAGES OF CELLULAR RESPIRATION AND FERMENTATION 6.6 Overview: Cellular respiration occurs in three main stages Cellular respiration Occurs in three main stages

  16. Do Now • What are the three stages of cellular respiration?

  17. 0 Stage 1: Glycolysis Occurs in the cytoplasm Breaks down glucose into pyruvate, producing a small amount of ATP

  18. 0 Stage 2: The citric acid cycle Takes place in the mitochondrial matrix Completes the breakdown of glucose, producing a small amount of ATP Supplies the third stage of cellular respiration with electrons

  19. 0 Stage 3: Oxidative phosphorylation Occurs in the mitochondria Uses the energy released by “falling” electrons to pump H+ across a membrane Harnesses the energy of the H+ gradient through chemiosmosis, producing ATP

  20. 0 NADH High-energy electrons carried by NADH NADH FADH2 and OXIDATIVEPHOSPHORYLATION(Electron Transport and Chemiosmosis) GLYCOLYSIS CITRIC ACID CYCLE Glucose Pyruvate http://www.youtube.com/watch?v=AdtAu5JgOV0&feature=related Mitochondrion Cytoplasm ATP CO2 CO2 ATP ATP Substrate-level phosphorylation Substrate-level phosphorylation Oxidative phosphorylation Figure 6.6

  21. 6.7 Glycolysis harvests chemical energy by oxidizing glucose to pyruvate “Splitting of sugar” Glycolysis is the universal energy-harvesting process of life.

  22. 0 H 2 + 2 NAD+ 2 NADH In glycolysis, ATP is used to prime a glucose molecule which is split into two molecules of pyruvate Glucose 2 Pyruvate + 2 2 P ATP 2 ADP Figure 6.7A

  23. 0 Enzyme Glycolysis produces ATP by substrate-level phosphorylation in which a phosphate group is transferred from an organic molecule to ADP P Adenosine P P ATP ADP P Organic molecule(substrate) P Figure 6.7B

  24. PREPARATORY PHASE(energy investment) 1 3  Steps      –   A fuel molecule is energized, using ATP. Glucose ATP Step 1 ADP Glucose-6-phosphate P In the first phase of glycolysis, ATP is used to energize a glucose molecule, which is then split in two small sugars that are now primed to release energy. 2 P Fructose-6-phosphate ATP 3 ADP P Fructose-1,6-diphosphate P  Step      A six-carbon intermediate splits into two three-carbon intermediates. 4 4 Figure 6.7C

  25. P P Glyceraldehyde-3-phosphate(G3P)  Step     A redox reaction generates NADH. 5 6 9 ENERGY PAYOFF PHASE NAD 5 5  NAD  P 6 6 P NADH NADH +H +H P P P P 1,3-Diphosphoglycerate  Steps     –      ATP and pyruvate are produced. 9 6 ADP ADP 6 6 7 7 ATP ATP P 3-Phosphoglycerate P In the second phase of glycolysis ATP, NADH, and pyruvate are formed 7 7 P P 8 8 2-Phosphoglycerate 8 8 H2O H2O P P Phosphoenolpyruvate(PEP) 9 9 ADP ADP 9 9 ATP ATP Pyruvate Figure 6.7C

  26. Glycolysis Overview The result of glycolysis is a conversion of glucose to two three-carbon compounds, that we call pyruvate. The end products of glycolysis are ATP, NADH, and pyruvate. Glycolysis Overview

  27.  H NADH NAD 6.8 Pyruvate is chemically groomed for the citric acid cycle Prior to the citric acid cycle, enzymes process pyruvate, releasing CO2 and producing NADH and acetyl CoA 2 CoA Pyruvate Acetyl CoA(acetyl coenzyme A) 1 3 CO2 Coenzyme A Figure 6.8

  28. Transition Between glycolysis and the citric acid cycle, pyruvate is oxidized (loses electrons) while a molecule of NAD+ is reduced (gains electrons) to NADH.

  29. 0 Acetyl CoA CoA CoA 6.9 The citric acid cycle completes the oxidation of organic fuel, generating many NADH and FADH2 molecules In the citric acid cycle, the two-carbon acetyl part of acetyl CoA is oxidized CO2 2 CITRIC ACID CYCLE NAD 3 FADH2 3 FAD NADH  3 H ADP  ATP P Figure 6.9A

  30. 0 The two carbons are added to a four-carbon compound, forming citrate Which is then degraded back to the starting compound

  31. CoA Acetyl CoA CoA 2 carbons enter cycle Oxaloacetate 1 For each turn of the cycle Two CO2 molecules are released The energy yield is one ATP, three NADH, and one FADH2 Citrate  H NADH 5 CO2 leaves cycle NAD 2 CITRIC ACID CYCLE NAD  H Malate NADH  P ADP FADH2 4 ATP Alpha-ketoglutarate FAD 3 CO2 leaves cycle Succinate  H NAD NADH Step 2 4 Steps 1 3 Steps and 5 and Acetyl CoA stokes the furnace. NADH, ATP, and CO2 are generated during redox reactions. Redox reactions generate FADH2 and NADH. Figure 6.9B

  32. Citric Acid Cycle The enzymes of the citric acid cycle are located in the mitochondrial matrix. At the end of the citric acid cycle, most of the energy remaining from the original glucose is stored in NADH. Citric Acid Cycle

  33. 0 6.10 Most ATP production occurs by oxidative phosphorylation Electrons from NADH and FADH2 Travel down the electron transport chain to oxygen, which picks up H+ to form water Energy released by the redox reactions Is used to pump H+ into the space between the mitochondrial membranes Overview http://www.youtube.com/watch?v=KXsxJNXaT7w&feature=related

  34. 0 H+ H+ H+ . H+ H+ Protein complex H+ H+ ATP synthase H+ Electron carrier H+ Intermembrane space In chemiosmosis, the H+ diffuses back through the inner membrane through ATP synthase complexes driving the synthesis of ATP. In the electron transport chain, the final electron acceptor is an oxygen atom. Electron Transport Chain Inner mitochondrial membrane FADH2 FAD Electron flow 1 +2 O2 H+ NAD+ NADH 2 H+ H+ Mitochondrial matrix  P ATP ADP H+ H2O H+ Chemiosmosis Electron Transport Chain OXIDATIVE PHOSPHORYLATION Figure 6.10

  35. 0 CONNECTION 6.11 Certain poisons interrupt critical events in cellular respiration Various poisons Block the movement of electrons Block the flow of H+ through ATP synthase Allow H+ to leak through the membrane Rotenone is a poison commonly added to insecticides. Insects exposed to rotenone will die because of inadequate ATP production. Figure 6.11

  36. Cyanide, carbon monoxide Rotenone Oligomycin H+ H+ H+ ATPSynthase H+ H+ H+ H+ H+ H+ DNP FAD FADH2  1 O2 2 H+ NADH NAD+ 2 H+  ATP P ADP H+ H2O H+ Electron Transport Chain Chemiosmosis

  37. 0 6.12 Review: Each molecule of glucose yields many molecules of ATP Oxidative phosphorylation, using electron transport and chemiosmosis Produces up to 38 ATP molecules for each glucose molecule that enters cellular respiration Electron shuttleacross membrane Mitochondrion 2 2 NADH NADH Cytoplasm (or 2 FADH2) 2 2 6 FADH2 NADH NADH OXIDATIVE PHOSPHORYLATION (Electron Transport and Chemiosmosis) GLYCOLYSIS 2 AcetylCoA 2 CITRIC ACIDCYCLE Glucose Pyruvate  about 34 ATP  2 ATP  2 ATP by substrate-level phosphorylation by oxidative phosphorylation by substrate-level phosphorylation About38 ATP Maximum per glucose: Figure 6.12

  38. Review Glycolysis and the citric acid cycle must occur two times per glucose molecule. The energy yield from the complete aerobic breakdown of a single molecule of glucose can vary with the mechanism used to shuttle NADH electrons into the mitochondrion. http://www.youtube.com/watch?v=AdtAu5JgOV0&feature=related http://www.youtube.com/watch?v=kN5MtqAB_Yc

  39. 0 6.13 Fermentation is an anaerobic alternative to cellular respiration Cellular respiration produces the most ATP per molecule of glucose oxidized. Under anaerobic conditions, many kinds of cells Can use glycolysis alone to produce small amounts of ATP

  40. 0 2 2 NADH 2 2 NAD NADH NAD In lactic acid fermentation NADH is oxidized to NAD+ as pyruvate is reduced to lactate Found in muscle cells and food products. GLYCOLYSIS P 2 ADP  2 ATP 2 2 Pyruvate 2 Lactate Glucose Figure 6.13A

  41. 0 NADH NAD 2 NAD NADH 2 2 2 In alcohol fermentation, NADH is oxidized to NAD+ while converting pyruvate to CO2 and ethanol Used in brewing, baking, and winemaking. GLYCOLYSIS 2 ADP  2 CO2 released 2 P 2 ATP 2 Ethanol Glucose 2 Pyruvate Figure 6.13B Figure 6.13C

  42. Strict Anaerobes-require anaerobic conditions and are poisoned by oxygen. Facultative Anaerobe-can make ATP either by fermentation or oxidative phosphorylation, depending on whether O2 is available. http://www.youtube.com/watch?v=y_k8xLrBUfg http://www.youtube.com/watch?v=tNqfPsVAdYk&feature=fvw

  43. 0 INTERCONNECTIONS BETWEEN MOLECULAR BREAKDOWN AND SYNTHESIS 6.14 Cells use many kinds of organic molecules as fuel for cellular respiration

  44. 0 Food, such aspeanuts Carbohydrates, fats, and proteins can all fuel cellular respiration when they are converted to molecules that enter glycolysis or the citric acid cycle Fats yield the most ATP. Carbohydrates Fats Proteins Sugars Fatty acids Amino acids Glycerol Aminogroups OXIDATIVEPHOSPHORYLATION(Electron Transportand Chemiosmosis) CITRICACIDCYCLE AcetylCoA Pyruvate Glucose G3P GLYCOLYSIS ATP Figure 6.14

  45. 0 ATP needed to drive biosynthesis ATP 6.15 Food molecules provide raw materials for biosynthesis Cells use some food molecules and intermediates from glycolysis and the citric acid cycle as raw materials Biosynthesis consumes ATP GLUCOSE SYNTHESIS CITRIC ACID CYCLE Acetyl CoA Glucose Pyruvate G3P Amino groups Fatty acids Amino acids Sugars Glycerol Carbohydrates Proteins Fats Cells, tissues, organisms Figure 6.15

  46. 0 6.16 The fuel for respiration ultimately comes from photosynthesis All organisms Can harvest energy from organic molecules Plants, but not animals Can also make these molecules from inorganic sources by the process of photosynthesis Figure 6.16

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