BBMB 405 1st Edition Lecture 5 Outline of Last Lecture VII Chapter 20 The Calvin Cycle and the Pentose Phosphate Pathway C The pentose phosphate Pathway Generates NADPH and Synthesizes Five Carbon Sugars 1 21 VIII Summary of Calvin Cycle IX Handout Physiological significance of hexose monophosphate pathway pentose phosphate pathway Outline of Current Lecture VII Chapter 20 The Calvin Cycle and the Pentose Phosphate Pathway C The pentose phosphate Pathway Generates NADPH and Synthesizes Five Carbon Sugars D The metabolism of Glucose 6 phosphate by pentose Phosphate pathway Is coordinated with glycolysis X Handout 1 23 Current Lecture VII Chapter 20 The Calvin Cycle and the Pentose Phosphate Pathway C The pentose phosphate Pathway Generates NADPH and Synthesizes Five Carbon Sugars 1 Mechanism transketolase and transaldolase stabilize carbanionic intermediates by different mechanisms a Transketolase mechanism These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute b Transaldolase reaction D The metabolism of Glucose 6 phosphate by pentose Phosphate pathway Is coordinated with glycolysis 1 Metabolic control of pentose phosphate pathway either glycolysis or pentose a Cytoplasmic concentration of NADP plays role in determining fate of glucose 6 phosphate G 6 P is converted to 6 PG via NADPH rate limiting step b Non oxidative reaction controlled by substrate and product of each reaction 2 The rate of pentose phosphate pathway is controlled by level of NADP2 a First step in oxidative branch of PPP pentose phosphate pathway is the dehydrogenation of G 6 P and is irreversible that is why NADPH is limiting cofactor b Effect or importance of NADPH NADP Ratio of NADP and NADPH in liver cell of rat is 0 014 which is several orders of magnitude lower than ration of NAD1 to NADH which is 700 effect on rate of oxidative phase ensures that NADPH is not made unless needed supply is low 3 The flow of glucose 6 phosphate depends on the need for NADPH ribose 5phosphate and ATP a b Mode 1 R 5 P need NADPH need generates intermediates used in rapidly dividing cells cancer cells need to replicate DNA quickly 5 Glucose 6 phosphate ATP 6 ribose 5 phosphate ADP 2 H c Mode 2 NADPH need R 5 P need used in liver for synthesis such as cholesterol d Mode 3 NADPH need R 5 P need functions as a cycle used in red blood cells need lots of NADPH and has no DNA RNA and adipose tissue for synthesis of fatty acids the glucose 6 phosphate can be completely oxidized to carbon dioxide with generation of NADPH e Mode 4 Both NADPH and ATP needed intermediates converted to pyruvate and burned used in developing brain still going through cell division or major cell division red blood cells epithelial cells bone marrow 4 Through the looking glass the Calvin cycle and the pentose phosphate pathway are mirror images look at them as similar and use that to help you study them many enzymes are common to both cycles X Handout 1 23 A Reduction of O2 1 Complete Reduction O2 4H 4e ETS 2H2O 2 Incomplete reduction oxidative stress causes problems in the body O2 e Superoxide ion very reactive O2 e Peroxide ion O22 2H Hydrogen peroxide H2O2 3 Protection against reactive oxygen species ROS a 2O2 2H superoxide dismutase SOD O2 H2O2 b SOD is deficient in ALS patients c 2H2O2 catalase O2 2H2O d H2O2 AH2 peroxidase 2H2O A e AH2 glutathione vitamin C cytochrome C quinones f Two reactions of catalase see handout 4 Protection with vitamin E and C react with O22 B Peroxidase catalase as protectant in bombardier beetle a 25 H2O2 Hydroquinone Peroxidase Catalase Hot boiling H2O b 3H2O2 hydroquinone Quinone 4H2O O2 heat C Electron Transport System and free radicals a See handout for radical reaction b Vitamin E protects against radicals neutralizes them c Rancidity d Lipid peroxidation in tissues free radicals steal electrons from lipids in cell membrane and cause cell damage e Malondialdehyde is used to measure peroxidation in tissues D G 6 P dehydrogenase deficiency a Inherited x linked recessive disorder b Cause G 6 P dehydrogenase deficiency causes low NADPH leading to cells being very sensitive to oxidative stress Low NADPH means low GSH which is needed for reducing H2O2 via GSH peroxidase c Symptom oxidative stress in RBC Hemolytic anemia too many cells break to fast recover new RBC d Stress increases via drugs or infection need of NADPH so increase production e Diagnosis assay of G 6 P dehydrogenase activity in RBC f Resistance to malaria lower infection in people with deficiency sickle cell anemia E Glycogen Metabolism a 10 of glycogen metabolism takes place in the liver b Major enzymes of glycogen metabolism i Synthesis glycogen synthase branching enzyme ii Degradation phosphorylase debranching enzyme alpha 1 6 glucosidase and transferase c See handout F Carl and Gerty Cori 1 26
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