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Cellular Respiration

Learn about cellular respiration and its role in providing energy for the body. Explore the Clothespin Challenge to understand how your muscles recover and the basics of metabolism. Discover the important reactions and steps involved in cellular respiration.

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Cellular Respiration

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  1. Cellular Respiration Giving you the energy you need!

  2. Clothespin Challenge! • Use your dominant hand • Open and close the pin (with your thumb and forefinger) as many times as you can for 20 seconds while holding the other fingers straight out! • Repeat for 5 more continuous trials! • Repeat for the non-dominant hand

  3. Clothespin Challenge! • What happened as time went on? • How did you hands feel at the end? • Was there a difference in dom and non-dom hands? • Why will your muscles recover in about 10 min?

  4. METABOLISM BASICS

  5. 1st Law of Thermodynamics • The total amount of energy in the universe is constant! • Energy cannot be created or destroyed but only converted to one form into another! • Activation Energy – Amount of E required to break chemical bonds

  6. 2nd Law of Thermodynamics • Entropy = Randomness and Chaos • Universe favours Entropy – think of how messy your room gets! • In all Rxns – Energy and Entropy are needed! • Spontaneous Human Combustion?

  7. ENDERGONIC REACTIONS • Energy of products more than reactants • Photosynthesis • Light energy converted to stored chemical energy C6H12O6 • Every molecule of glucose contains 2870kJ

  8. Photosynthesis

  9. EXERGONIC REACTIONS • Energy of products is less than reactants • Free energy is released! • Cellular respiration • The energy from glucose is released and harnessed into ATP at a controlled rate!

  10. Cellular Respiration

  11. Cellular Respiration Overview • The Goal of C.R. is to create ATP from Glucose! • See handout! • Four main parts... • Glycolysis • Pyruvate Oxidation • Krebs Cycle (Citric Acid Cycle) • Electron Transport Chain

  12. Important Reactions! • Redox Reactions • Substrate Level Phosphorylation • Oxidative Phosphorylation • These rxns occur frequently throughout the cellular respiration pathways!

  13. Redox Reactions • Energy metabolism in cells involves oxidation reactions. • Oxidation involves the transfer of an electron from a molecule, which is said to be oxidized, to another molecule, which is said to be reduced. • An oxidation cannot occur without a corresponding reduction. They are PAIRED reactions. • Many important redox reactions in cells require the presence of coenzymes. • The redox reactions of cellular respiration commonly involve the following coenzymes:

  14. RedoxRxnsMake Energy Carriers 1) NAD: Nicotinamide adenine dinucleotide NAD+ + 2 e- + 2 H+ → NADH + H+   *the second H+ dissolves into cytosol * 2) FAD: Flavin adenine dinucleotide FAD + 2e- + 2 H+ → FADH2

  15. A Memory Trick! • LEO the lion says GER • Lose • Electrons • Oxidized! SAYS... • Gain • Electrons • Reduced!

  16. “Reduced” means that the overall positive charge of the molecule has decreased (due to accepting the electons!)

  17. Substrate Level Phosphorylation • A mechanism forming ATP directly in an enzyme-catalyzed reaction ATPase • ADP + Pi + 31 kJ/mole ATP • This is called Phosphorylation... The opposites is called Dephosphorylation • A single muscle cell uses 600 million ATP per minute • The body consumes its own mass in ATP per day via constant recycling!

  18. Oxidative Phosphorylation • ATP formed in-directly • Uses redox rxns (see previous slides) • NADH • FADH2 • These molecules harvest energy and transfer it to ATP by the end of Cellular Resp.

  19. STEP 1 - Glycolysis • A glucose is broken down into 2 Pyruvate molecules • Brief overview... • http://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter25/animation__how_glycolysis_works.html • Occurs in the cytoplasm • Anaerobic (doesn’t need oxygen!) • See handout!!

  20. Glycolysis cont. Recall that there are 2 GAP per glucose.

  21. Glycolysis Balance sheet for ~P bonds of ATP: • How many ATP ~P bonds expended? ________ • How many ~P bonds of ATP produced? (Remember there are two 3C fragments from glucose.) ________ • Net production of ~P bonds of ATP per glucose: ________ 2 4 2

  22. Overall Equation Glucose + 2 ADP + 2 Pi + 2 NAD+ 2 Pyruvate + 2 ATP + 2 (NADH + H+)

  23. Is Glycolysis Efficient? • 2.2% of E from glucose is transferred to ATP via Glycolysis. • This might be good enough for some micro-organisms but not larger species like ourselves! • A much more detailed look... http://www.youtube.com/watch?v=O5eMW4b29rg&feature=related • Page 115 #1-7

  24. Mitochondrion Anatomy

  25. STEP 2 -Pyruvate Oxidation • Occurs in the Matrix • See P 100 for a great diagram • General Equation... • CoA = coenzyme A 2 Pyruvate + 2 NAD+ + 2 CoA 2 acetylCoA + 2 NADH + 2H+ +2CO2 Acetyl CoA then enters the Kreb Cycle!!

  26. STEP 3 - Krebs Cycle • In mitochondrion • Mostly on inner membrane • Many enzymes, coenzymes and other molecules are in an organize pattern on the inner membrane. • Brief Overview... http://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter25/animation__how_the_krebs_cycle_works__quiz_1_.html

  27. Krebs Cycle • More depth! • http://www.youtube.com/watch?v=A1DjTM1qnPM • Note where H2O is used and CO2 is released!

  28. The Balance Sheet so far... • By the end of the Krebs Cycle (thru Steps 1-3) the entire glucose molecule is consumed. • 6C get converted to 6 CO2 along the way! • HARNESSED ENERGY (NET)! • 4 ATP (2 Glycolysis, 2 Krebs) • 12 reduced coenzymes: • 2 NADH (Glycolysis) • 2 NADH (Pyruvate Oxidation stage) • 6 NADH (Krebs) • 2FADH2 (Krebs)

  29. STEP 4 – The Electron Transport Chain

  30. ETC Details... • Occurs on the inner membrane of mito • Transports electrons (from NADH and FADH2) thru a series of redoxrxns that release free energy. • This free energy is used to pump H+ protons into the inner membrane space of the mitochondria • This creates an electro-chemical gradient that is a source of free energy which is used to create ATP!

  31. The Key Structures...

  32. ETC • Overheads • Visuals... • http://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter25/animation__electron_transport_system_and_atp_synthesis__quiz_1_.html • http://www.youtube.com/watch?v=0LcWbKOW0u8&feature=related

  33. The Importance of Oxygen • Oxygen is the final acceptor of electrons that pass thru the ETC!! • Its high electronegativity pulls the electrons through the ETC • Electrons fall (like a skydiver)...this energy pumps H+ ions into the inner membrane space so they can “fall” back into the matrix and make ATP!

  34. Chemiosmosis • Protons move through a Proton Channel and ATP synthase to produce ATP molecules • Oxidative Phosphorylation!! • Electrochemical Gradient must be maintained (by eating!) or ATP production stops!

  35. Protons(indicated by + charge) enter back into the mitochondrial matrix through channels in ATP synthase enzyme complex. This entry is coupled to ATP synthesis from ADP and phosphate (Pi)

  36. What happens to the NADH from Glycolysis? • NADH diffuses thru the inner membrane via the glycerol-phosphate shuttle (P105) • NADH passes electrons to FAD to make FADH2 • NADH can also pass electrons to NAD+ in the matix via the aspartate shuttle (less common!)

  37. NADH vs. FADH2 • In simplified terms NADH pumps 3 H+ ions across...therefore creating 3 ATP molecules! • FADH2 enters the ETC at Q...therefore only pumping 2 H+ ions across and making 2 ATP molecules!

  38. Aerobic Respiration Efficiency • Theoretical and Actual Yields • Actual...depends on environment (ie temp) • Theoretical – 36 ATP • Actual yield is less...heat loss, H+ ions leaking...Approx 30 ATP?? • Aerobic C.R. Is approx 32% efficient

  39. Final Balance Sheet • See page 110 and page 114 • To review all 4 Steps...See these interactive animations... • http://www.science.smith.edu/departments/Biology/Bio231/ • Page 115 - #8-18

  40. Metabolic Rate • An organism’s Metabolic rate is the amount of energy consumed at a given time and a measure of the overall rate of C.R. Rxns!

  41. Control Mechanisms (p 113) • Phosphofructokinase (catalyzes step 3 of Glycolysis) controls C.R. • It is activated by ADP and inhibited by ATP • NADH inhibits pyruvate decarboxylase and prevents Acetyl-CoA from forming • An organism’s Metabolic Rate is the amount of energy consumed by an organism in a given time.

  42. Related Pathways

  43. Protein Catabolism • PRO’s Broken down into individual A.A.’s in the body. • First stage of this is deamination (removal of amino group as ammonia NH3), a waste. • The remaining parts of the A.A.’s are converted into components of glycolysis or Krebs cycle

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