Carbohydrate metabolism

1. Chapter 3 • Coupled reactions • The additivity of free energy changes allows an endergonic reaction to be driven by an exergonic reaction under the proper conditions. (thermodynamic basis for the operation of the metabolic pathways since most of these reaction sequences comprise endergonic as well as exergonic reactions. Carbohydrate metabolism

2. - Also known as Respiration. - Comprises of these different processes depending on type of organism: I. Anaerobic Respiration II. Aerobic Respiration Break-down of glucose to generate energy

3. Anaerobic Respiration Comprises of these stages: glycolysis: glucose 2 pyruvate + NADH fermentation: pyruvate lactic acid or ethanol cellular respiration:

4. Comprises of these stages: Oxidative decarboxylation of pyruvate Citric Acid cycle Oxidative phosphorylation/ Electron Transport Chain(ETC) Aerobic Respiration

5. Brief overview of catabolism of glucose to generate energy STARCHY FOOD α – AMYLASE ; MALTASES Glucose Glucose converted to glu-6-PO4 Start of cycle Glycolysis in cytosol Cycle : anaerobic Aerobic condition; in mitochondria 2[Pyruvate+ATP+NADH] Pyruvate enters as AcetylcoA Anaerobiccondition - Krebs Cycle - E transport chain Lactic Acid fermentation in muscle. Only in yeast/bacteria Anaerobic respiration or Alcohol fermentation

6. Show time.. GLYCOLYSIS

7. 1st stage of glucose metabolism → glycolysis An anaerobic process, yields 2 ATP (additional energy source) Glucose will be metabolized via gycolysis; pyruvate as the end product The pyruvate will be converted to lactic acid (muscles → liver) Aerobic conditions: the main purpose is to feed pyruvate into TCA cycle for further rise of ATP Glycolysis

8. The breakdown of glucose to pyruvate as summarized: Glucose (six C atoms) → 2 pyruvate (three C atoms) 2 ATP + 4 ADP + 2 Pi → 2 ADP + 4 ATP (phosphorylation) Glucose + 2 ADP + 2 Pi → 2 Pyruvate + 2 ATP (Net reaction) Fig. 17-1, p.464

9. Fig. 17-2, p.465

10. Louis Pasteur • French biologist • did research on fermentation which led to important discoveries in microbiology and chemistry

11. How 6-carbon glucose converted to the 3-carbon glyceraldehyde-3-phosphate? Preparation phase Step 1 Glucose is phosphorylated to give gluc-6-phosphate p.467

12. Fig. 17-3, p.468

14. Table 17-1, p.469

15. Fig. 17-4, p.470

16. Glucose-6-phosphate isomerize to give fructose-6-phosphate Step 2 p.470a

17. Step 3 Fructose-6-phosphate is phosphorylated producing fructose-1,6-bisphosphate p.470b

18. Fig. 17-6, p.471

19. Step 4 Fructose-1,6-bisphosphate split into two 3-carbon fragments p.471a

20. Step 5 Dihydroxyacetone phosphate is converted to glyceraldehyde-3-phosphate p.471b

21. How is glyceraldehyde-6-phosphate converted to pyruvate Payoff phase Step 6 Glyceraldehyde-6-phosphate is oxidized to 1,3-bisphosphoglycerate p.472

22. Fig. 17-7, p.473

24. p.474a

25. Fig. 17-8, p.475

26. Step 7 Production of ATP by phosphorylation of ADP p.476

27. Step 8 Phosphate group is transferred from C-3 to C-2 p.477a

28. Step 9 Dehydration reaction of 2-phosphoglycerate to phosphoenolpyruvate p.477b

29. Step 10 Phosphoenolpyruvate transfers its phosphate group to ADP → ATP and pyruvate p.478

30. Control points in glycolysis Fig. 17-10, p.479

31. How is pyruvate metabolized anaerobically? Conversion of pyruvate to lactate in muscle p.479

32. Fig. 17-11b, p.481

33. Pyruvate decarboxylase Fig. 17-11a, p.481

34. Fig. 17-12, p.482

35. Acetaldehyde + NADH → Ethanol + NAD+ Glucose + 2 ADP + 2 Pi + 2 H+ → 2 Ethanol + 2 ATP + 2 CO2 + 2 H2O p.482

36. Carbohydrate metabolism Chapter 3 (cont.)

37. Gluconeogenesis • Conversion of pyruvate to glucose • Biosynthesis and the degradation of many important biomolecules follow different pathways • There are three irreversible steps in glycolysis and the differences bet. glycolysis and gluconeogenesis are found in these reactions • Different pathway, reactions and enzyme STEP 1 p.495

38. is the biosynthesis of new glucose from non-CHO precursors. • this glucose is as a fuel source by the brain, testes, erythrocytes and kidney medulla • comprises of 9steps and occurs in liver and kidney • the process occurs when quantity of glycogen have been depleted - Used to maintain blood glucose levels. • Designed to make sure blood glucose levels are high enough to meet the demands of brain and muscle (cannot do gluconeogenesis). • promotes by low blood glucose level and high ATP • inhibits by low ATP • occurs when [glu] is low or during periods of fasting/starvation, or intense exercise • pathway is highly endergonic *endergonic is energy consuming

39. STEP 2

40. The oxalocetate formed in the mitochondria have two fates: - continue to form PEP - turned into malate by malate dehydrogenase and leave the mitochondria, have a reaction reverse by cytosolic malate dehydrogenase • Reason?

42. as • Controlling glucose metabolism • found in Cori cycle • shows the cycling of glucose due to gycolysis in muscle and gluconeogenesis in liver • This two metabolic pathways are not active simultaneously. • when the cell needs ATP, glycolisys is more active • When there is little need for ATP, gluconeogenesis is more active As energy store for next exercise Fig. 18-12, p.502

43. Cori cycle requires the net hydrolysis of two ATP and two GTP.

44. Fig. 18-13, p.503

45. The Citric Acid cycle • Cycle where 30 to 32 molecules of ATP can be produced from glucose in complete aerobic oxidation • Amphibolic – play roles in both catabolism and anabolism • The other name of citric acid cycle: Krebs cycle and tricarboxylic acid cycle (TCA) • Takes place in mitochondria

46. Fig. 19-2, p.513

48. Steps 3,4,6 and 8 – oxidation reactions Fig. 19-3b, p.514

49. 5 enzymes make up the pyruvate dehydrogenase complex: • pyruvate dehydrogenase (PDH) • Dihydrolipoyl transacetylase • Dihydrolipoyl dehydrogenase • Pyruvate dehydrogenase kinase • Pyruvate dehydrogenase phosphatase Conversion of pyruvate to acetyl-CoA

50. Step 1 Formation of citrate p.518