Glycolysis Slides & Notes PDF

Fast Glycolysis  Glycolysis Energy Investment or Preparatory Phase...

Fast Glycolysis  Glycolysis Energy Investment or Preparatory Phase (Steps 1‐4) * Edited for  “Stage 1” clarity *  Rapid energy production Substrate‐level Phosphorylation  “Anaerobic” glycolysis Energy Production / Payoff or  “Fast” glycolysis Phase (Steps 6‐10)  “Lactic acid” system  Occurs in the sarcoplasm (cytosol) Glucose → 2 Lactate + 2 ATP Lactate Lactate Fig. 2.7. Kenney et al. 2015. Physiology of Sport… Hum.Kin.  Glycolysis: Prep. Phase (Step 1) 3 1) Hexokinase reaction uses an ATP to phosphorylate glucose and “trap” it in the cell  Coupled reaction of Glucose to G6P (anabolic) and ATP to ADP (catabolic)  Reaction is irreversible in muscle Glucokinase adds the phosphate in liver Liver also has glucose 6‐phosphatase to remove it Know structure & rxn Glucose Glucose‐6‐phosphate (G6P) (C6H12O6)  Glycolysis: Prep. Phase (Step 2) 4 2) Phospho‐gluco‐isomerase rearranges the structure to convert G6P into F6P  Converts it from a hexagon shape (glucose) to a pentagon shape (fructose) Recall, that glucose & fructose are isomers because they have the same chemical formula (C6H12O6), but different shapes. Glucose Glucose‐6‐phosphate (G6P) Fructose‐6‐phosphate (F6P)  Glycolysis: Prep. Phase (Step 3) 5 3) Phosphofructokinase (PFK) adds a 2nd phosphate to F6P to make it FDP  This coupled reaction is irreversible and commits it to the rest of glycolysis  Rate‐limiting step of glycolysis Speed of glycolysis is determined by regulating PFK Important for fast twitch (Type II fibers) Phosphofructokinase Fructose 1,6‐diphosphate (F1,6P) or (FDP) Know structure & rxn  Glycolysis: Prep. Phase (Step 4) 6 4) Aldolase splits FDP into two 3‐C skeletons Phosphofructokinase PFK made it symmetrical, * Edited for so it could be split in half clarity * Step 5 involves conversion to two equal G3Ps (glyceraldehyde 3 Aldolase phosphate) Leads from the Energy Investment to the “Payoff” Phase A (a.k.a. G3P) Fig. 2.7a. Kenney et al. 2015. Physiology of Sport… Hum.Kin. Anaerobic Glycolysis 7 (a.k.a. G3P) G3P  Substrate‐level dehydrogenase Phosphorylation or Energy Generation Phase  Mainly understand what generally 1,3 DPG kinase happens in these 3 steps 6) G3P dehydrogenase oxidizes G3P & reduces NAD+  NADH & H+ to ETC or LDH 7) 1,3DPG kinase 2 ATP produced 10) Pyruvate kinase 2 ATP & 2 Pyruvate produced Pyruvate kinase  Produce 4 total ATP and NET 2 ATP from anaerobic glycolysis of Lactate Lactate 7 glucose Fig. 2.7b. Kenney et al. 2015. Physiology of Sport… Hum.Kin.  Glycolysis Overview  Know Steps 1‐4 of glycolysis in detail  Know generally what is produced in steps 6,7,10.  You do not need to know each enzyme and substrate for these steps.  The enzyme type & (side arrow) products are more important for these. Except Step 10 where it is important to know that pyruvate is the end product. Fig. 7.7. Thompson et al. 2011. Science of Nutrition 2/e. Pearson 9 Lactate Lactate Fig. 2.7a. Kenney et al. 2015. Physiology of Sport… Hum.Kin.  Glycogenesis 10  Glycogen synthase Glycogen  Stimulated by low Synthase cellular activity / following a meal Hexokinase  Stored in the cytoplasm Fig. 3.14. Powers & Howley. 2012. Exercise Physiology… McGraw-Hill Glycogenesis vs. Glycogenolysis 11  Glycogenesis: Glycogen synthase  Glycogenolysis: Glycogen phosphorylase  Stimulated by high cellular activity Epinephrine release during intense activity Calcium release  Adds a Pi Converted to G6P  Adds 1 net ATP with glycolysis  You do not need to know the specific steps of this process Fig. 1.3. McArdle et al. 2010. Exercise Physiology… LWW  Glycogenolysis * Edited for clarity *  An extra ATP is net when using glycogen as a substrate  The HK rxn is bypassed and you don’t have to invest that ATP Fig. 2.7. Kenney et al. 2015. Physiology of Sport… Hum.Kin. Review Questions 13  Explain the purpose of the 2 stages of glycolysis  Know and be able to write the first 4 reactions of glycolysis  Explain the significance of the HK and PFK rxns  Be able to identify the substrates and products of the specific components of the coupled reactions (e.g. exergonic rxns, etc.)  Recognize the structure of glucose and fructose and be able to distinguish their phosphorylated forms  Know the type of rxns that yield ATP and NADH in the second stage of glycolysis  Explain how it is determined whether G6P is converted to glycogen or F6P  Why is glycogen preferred over glucose for glycolysis during exercise?  Why does using glycogen as a substrate net an extra ATP? Figure & Notes References 14  Kenney, Wilmore, & Costill. Physiology of Sport & Exercise, 5th Edition. Human Kinetics, 2015.  McCardle, Katch, Katch. Exercise Physiology: Nutrition, Energy, and Human Performance, 8th Edition. Wolters Kluwer Health, 2015.  Baechle & Earle. Essentials of Strength & Conditioning, 3rd Edition. Human Kinetics, 2009.  Thompson, Manore, Vaughan. The Science of Nutrition, 2nd Edition. Pearson Education Inc., 2011. You should know these 4 steps of glycolysis in detail. Be able to recognize the structures of glucose and fructose. Common abbreviations: HK = hexokinase; G6P = glucose 6‐phosphate; F6P = fructose 6‐phosphate; PFK = phosphofructokinase; G3P = glyceraldehyde 3‐phosphate The HK and PFK reactions are irreversible in the muscle. The liver has glucokinase instead of hexokinase. Since GK is a weaker enzyme, then the liver can use glucose‐6‐ phosphatase to remove the phosphate from G6P and allow glucose to leave the cell. G6P is either used to build glycogen or sent through glycolysis depending on the energy status of the cell. Glucose and Fructose are isomers because they have the same chemical formula (C6H12O6), but different structures. You should understand why HK commits glucose to the cell and why PFK commits it to glycolysis. The product of PFK is fructose 1,6‐diphosphate (F16P) which is sometimes called fructose 1,6‐bisphosphate Aldolase splits F16P into two 3 carbon structures that are not quite symmetrical. Step 5 is there to make these 3C structures identical. Note that 3‐phosphoglyceraldehyde is the same thing as glyceraldehyde 3‐phosphate (G3P). Thus far, you have invested 2 ATP (at steps 1 & 3) in the Energy Investment Phase of Glycolysis 2