1 / 37

Outline

Outline. Glycolysis Transition Reaction Citric Acid Cycle Electron Transport System Fermentation Metabolic Pool Catabolism Anabolism. Cellular Respiration. A cellular process that requires oxygen and gives off carbon dioxide

Download Presentation

Outline

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Cellular Respiration

  2. Outline • Glycolysis • Transition Reaction • Citric Acid Cycle • Electron Transport System • Fermentation • Metabolic Pool • Catabolism • Anabolism

  3. Cellular Respiration • A cellular process that requires oxygen and gives off carbon dioxide • Usually involves breakdown of glucose to carbon dioxide and water • Energy extracted from glucose molecule: • Released step-wise • Allows ATP to be produced efficiently • Oxidation-reduction enzymes include NAD+ and FAD as coenzymes

  4. Glucose Breakdown:Summary Reaction

  5. NAD+ and FAD • NAD+ (nicotinamide adenine dinucleotide) • Called a coenzyme of oxidation-reduction it can • Oxidize a metabolite by accepting electrons • Reduce a metabolite by giving up electrons • Each NAD+ molecule used over and over again • FAD (flavin adenine dinucleotide) • Also a coenzyme of oxidation-reduction • Sometimes used instead of NAD+ • Accepts two electrons and two hydrogen ions (H+) to become FADH2

  6. NAD+ Cycle

  7. Cellular Respiration:Overview of 4 Phases • Glycolysis: • Occurs in cytoplasm • Glucose broken down to two molecules of pyruvate • ATP is formed • Transition reaction: • Both pyruvates are oxidized • Electron energy is stored in NADH • Two carbons are released as CO2 • Citric acid cycle: • Electron energy is stored in NADH and FADH2 • ATP is formed • Four carbons are released as CO2 • Electron transport chain: • Extracts energy from NADH & FADH2 • Produces 32 or 34 molecules of ATP

  8. Glucose Breakdown:Overview of 4 Phases

  9. Glucose Breakdown:Glycolysis • Occurs in cytoplasm outside mitochondria • Energy Investment Steps: • Two ATP are used to activate glucose • Glucose splits into two G3P molecules • Energy Harvesting Steps: • Two electrons (as hydrogen atoms) are picked up by two NAD+ • Four ATP produced by substrate-level phosphorylation • Net gain of two ATP • Both G3Ps converted to pyruvates

  10. Glycolysis:The Balance Sheet

  11. Substrate-level Phosphorylation

  12. Glycolysis

  13. Glycolysis

  14. Glucose Breakdown:The Preparatory (Prep) Reaction • End product of glycolysis, pyruvate, enters the mitochondrial matrix • Pyruvate converted to 2-carbon acetyl group • Attached to Coenzyme A to form acetyl-CoA • Electron picked up (as hydrogen atom) by NAD+ • CO2 released, and transported out of mitochondria into the cytoplasm

  15. Mitochondrion:Structure & Function

  16. Preparatory Reaction

  17. Glucose Breakdown:The Citric Acid Cycle • A.K.A. Krebs cycle • Occurs in matrix of mitochondria • Both acetyl (C2) groups received from the preparatory reaction: • Join with an enzyme CoA molecule to make acetyl-CoA • Acetyl (C2) group transferred to oxaloacetate (C2) to make citrate (C6) • Each acetyl oxidized to two CO2 molecules • Remaining 4 carbons from oxaloacetate converted back to oxaloacetate (thus “cyclic”) • NADH, FADH2 capture energy rich electrons • ATP formed by substrate-level phosphorylation

  18. The Citric Acid Cycle

  19. Citric Acid Cycle:Balance Sheet

  20. Electron Transport Chain • Location: • Eukaryotes: cristae of the mitochondria • Aerobic Prokaryotes: plasma membrane • Series of carrier molecules: • Pass energy rich electrons along • Complex arrays of protein and cytochromes • Cytochromes are respiratory molecules • Complex carbon rings with metal atoms in center • Receives electrons from NADH & FADH2 • Produce ATP by oxidative phosphorylation

  21. Electron Transport Chain • The fate of the hydrogens: • Hydrogens from NADH deliver enough energy to make 3 ATPs • Those from FADH2 have only enough for 2 ATPs • “Spent” hydrogens combine with oxygen • Recycling of coenzymes increases efficiency • Once NADH delivers hydrogens, it returns (as NAD+) to pick up more hydrogens • However, hydrogens must be combined with oxygen to make water • If O2 not present, NADH cannot release H • No longer recycled back to NAD+

  22. Electron Transport Chain

  23. Organization of Cristae

  24. Glucose Catabolism:Overall Energy Yield • Net yield per glucose: • From glycolysis – 2 ATP • From citric acid cycle – 2 ATP • From electron transport chain – 32 ATP • Energy content: • Reactant (glucose) 686 kcal • Energy yield (36 ATP) 263 kcal • Efficiency 39%; balance is waste heat

  25. Overall Energy Yieldedper Glucose Molecule

  26. Fermentation (1) • When oxygen limited: • Spent hydrogens have no acceptor • NADH can’t recycle back to NAD+ • Glycolysis stops because NAD+ required • Fermentation: • “Anaerobic” pathway • Can provide rapid burst of ATP • Provides NAD+ for glycolysis • NADH combines with pyruvate to yield NAD+

  27. Fermentation

  28. Fermentation (2) • Pyruvate reduced by NADH to: • Lactate • Animals & some bacteria • Cheese & yogurt; sauerkraut • Ethanol & carbon dioxide • Yeasts • Bread and alcoholic beverages • Allows glycolysis to proceed faster than O2 can be obtained • Anaerobic exercise • Lactic acid accumulates • Causes cramping and oxygen debt • When O2 restored, lactate broken down to acetyl-CoA and metabolized

  29. Products of Fermentation

  30. Efficiency of Fermentation InLine Figure 143

  31. Metabolic Pool:Catabolism (1) • Foods: • Sources of energy rich molecules • Carbohydrates, fats, and proteins • Catabolism (breakdown side of metabolism) • Breakdown products enter into respiratory pathways as intermediates • Carbohydrates • Converted into glucose • Processed as above

  32. The Metabolic Pool Concept

  33. Metabolic Pool:Catabolism (2) • Breakdown products enter into respiratory pathways as intermediates (cont.) • Proteins • Broken into amino acids (AAs) • Some AAs used to make other proteins • Excess AAs deaminated (NH2 removed) in liver • Results in poisonous ammonia (NH3) • Quickly converted to urea • Different R-groups from AAs processed differently • Fragments enter respiratory pathways at many different points

  34. Metabolic Pool:Anabolism (1) • All metabolic reactions part of metabolic pool • Intermediates from respiratory pathways can be used for anabolism • Anabolism (build-up side of metabolism): • Carbs: • Start with acetyl-CoA • Basically reverses glycolysis (but different pathway) • Fats • G3P converted to glycerol • Acetyls connected in pairs to form fatty acids • Note – dietary carbohydrate RARELY converted to fat in humans!

  35. Metabolic Pool:Anabolism (2) • Anabolism (cont.): • Proteins: • Made up of combinations of 20 different amino acids • Some amino acids (11) can be synthesized from respiratory intermediates • organic acids in citric acid cycle can make amino acids • Add NH2 – transamination • However, other amino acids (9) cannot be synthesized by humans • Essential amino acids • Must be present in diet or die

  36. Review • Glycolysis • Transition Reaction • Citric Acid Cycle • Electron Transport System • Fermentation • Metabolic Pool • Catabolism • Anabolism

  37. Cellular Respiration

More Related