Biokimia Karbohidrat, Metabolisme Energi, Dan Ketegenesis

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Transcript of Biokimia Karbohidrat, Metabolisme Energi, Dan Ketegenesis

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An Overview of MetabolismFigure 22-2Summary of Metabolism

CarbohydratesFatsFree fatty acids + glycerolFatstoresGlucoseExcess glucoseGlycogenstoresAminoacidsProteinsDIETLipogenesisBrainmetabolismRange of normalplasma glucoseGluconeogenesisBodyproteinGlycogenolysisGlycogenesisProteinsynthesisMetabolism inmost tissuesFree fattyacid poolUrineExcess nutrientsLipogenesisLipolysisGlucose poolAmino acidpoolCopyright 2007 Pearson Education, Inc., publishing as Benjamin Cummings3Figure 22-2 (1 of 4)Summary of Metabolism

CarbohydratesFatstoresGlucoseExcess glucoseGlycogenstoresDIETLipogenesisBrainmetabolismRange of normalplasma glucoseGlycogenolysisGlycogenesisMetabolism inmost tissuesUrineGlucose poolCopyright 2007 Pearson Education, Inc., publishing as Benjamin Cummings4Figure 22-3MetabolismSummary of biochemical pathways for energy production

GlucoseSomeaminoacidsSomeaminoacidsLactateGlycogenGlucose 6phosphateLiver onlyFattyacidsElectron transportsystemCO2NH3O2CoAKetonebodies (in liver)Glycerol2 ATPATP + H2OGLYCOLYSISPyruvatePyruvateAcetyl CoANH3CytoplasmMitochondriaCitricacidcycle2 ATPAnaerobic conditions Aerobic conditionsCopyright 2007 Pearson Education, Inc., publishing as Benjamin Cummings5Figure 22-4MetabolismPush-pull control of metabolism

Copyright 2007 Pearson Education, Inc., publishing as Benjamin Cummings6Metabolism

Copyright 2007 Pearson Education, Inc., publishing as Benjamin Cummings7Carbohydrate MetabolismPrimarily glucoseFruktosa dan galaktosa memasuki jalur-jalur pada berbagai titikSemua sel dapat memanfaatkan glukosa untuk produksi energiGlukosa serapan dari darah ke sel-sel biasanya dimediasi oleh insulin dan transporterLiver is central site for carbohydrate metabolismGlucose uptake independent of insulinThe only exporter of glucoseBlood Glucose HomeostasisBeberapa jenis sel lebih memilih glukosa sebagai sumber energi (ex., CNS) 80-126 mg/dl is normal range of blood glucose in fasted state < 200 mg/dl is normal range of blood glucose in post prandial Uses of glucose: Energy source for cells Muscle glycogen Fat synthesis if in excess of needs Fates of GlucoseFed stateStorage as glycogenLiverSkeletal muscleStorage as lipidsAdipose tissueFasted stateMetabolized for energyNew glucose synthesizedSynthesis and breakdown occur at all times regardless of state...

The relative rates of synthesis and breakdown changeHigh Blood GlucoseGlucose absorbedInsulin: GlucagonPancreasMuscleAdipose CellsGlycogenGlucose absorbedGlucose absorbedimmediately after eating a mealGlucose MetabolismFour major metabolic pathways:

Energy status of body regulates which pathway gets energy Immediate source of energy Pentophosphate pathway Glycogen synthesis in liver/muscle Precursor for triacylglycerol synthesisFate of Absorbed Glucose1st Priority: glycogen storageStored in muscle and liver2nd Priority: provide energyOxidized to ATP3rd Priority: stored as fatOnly excess glucose Stored as triglycerides in adiposeEnergy StoresPentose Phosphate PathwayGlycolysisEnergy StoresPentose Phosphate PathwayGlycolysisLiver710% of wet weightUse glycogen to export glucose to the bloodstream when blood sugar is lowGlycogen stores are depleted after approximately 24 hrs of fasting (in humans)De novo synthesis of glucose for glycogen GlycogenesisGlycogenesisSkeletal muscle1% of wet weightMore muscle than liver, therefore more glycogen in muscle, overallUse glycogen (i.e., glucose) for energy only (no export of glucose to blood)Use already-made glucose for synthesis of glycogenEnergy StoresPentose Phosphate PathwayGlycolysisGlycolysisUrutan reaksi yang mengubah glukosa menjadi piruvat Jumlah energi yang dihasilkan relatif kecil Reaksi glikolisis terjadi dalam sitoplasmaTidak memerlukan oksigenGlucose Pyruvate Lactate (animals)Acetyl-CoA (TCA cycle)Ethanol (yeast)

GlycolysisGlucose + 2 ADP + 2 Pi 2 Lactate + 2 ATP + 2 H2OFirst Reaction of Glycolysis

Perangkap glukosa dalam sel (ireversibel dalam sel otot)

Heksokinase digunakan oleh sebagian besar tanaman, hewan,dan mikroba untuk memfosforilasi glukosa

Glukokinase dalam jaringan hatiGlycolysis - SummaryGlucose2 Pyruvate2 ATP2 ADP4 ADP4 ATP2 NAD2 NADH + H

carbohydrate metabolism

Pyruvate MetabolismThree fates of pyruvate: Conversion to lactate (anaerobic) Conversion to alanine (amino acid) Entry into the TCA cycle via pyruvate dehydrogenase pathwayAnaerobic Metabolism of PyruvateProblem:Selama glikolisis, NADH terbentuk dari NAD +Tanpa O2, NADH tidak dapat dioksidasi menjadi NAD +Tidak ada lagi NAD +Semua dikonversi menjadi NADHTanpa NAD +, glikolisis berhenti ...Anaerobic Metabolism of PyruvateSolution:Hidupkan NADH kembali ke NAD + dengan membuat laktat (asam laktat)

(oxidized)(reduced)(oxidized)(reduced)Anaerobic Metabolism of PyruvateATP yieldTwo ATPs (net) are produced in the anaerobic breakdown of one glucoseThe 2 NADHs are used to reduce 2 pyruvate to 2 lactateReaction is fast and doesnt require oxygenPyruvate Metabolism - AnaerobicPyruvateLactateNADH NAD+Lactate DehydrogenaseLaktat dapat diangkut oleh darah ke hati dan digunakan dalam glukoneogenesisCori Cycle

Laktat diubah menjadi piruvat di hatiPyruvate MetabolismThree fates of pyruvate: Conversion to lactate (anaerobic) Conversion to alanine (amino acid) Entry into the TCA cycle via pyruvate dehydrogenase pathwayPyruvate metabolismConvert to alanine and export to blood

Keto acidAmino acidPyruvate MetabolismThree fates of pyruvate: Conversion to lactate (anaerobic) Conversion to alanine (amino acid) Entry into the TCA cycle via pyruvate dehydrogenase pathwayGlycolysis

Pyruvate Dehydrogenase Complex (PDH)Prepares pyruvate to enter the TCA cycle

Electron Transport ChainTCA CycleAerobic ConditionsPDH - SummaryPyruvateAcetyl CoA2 NAD2 NADH + HCO2TCA CycleDalam kondisi aerobik Link siklus TCA piruvat untuk fosforilasi oksidatifTerjadi pada mitokondriaMenghasilkan 90% dari energi yang dilepaskan dari makanan

Strateginya adalah untuk mengoksidasi asetil-KoA menjadi CO2 dan menangkap energi NADH (FADH2) dan ATP Metabolizes carbohydrate, protein, and fat

TCA Cycle - SummaryAcetyl CoA3 NAD3 NADH + H1 FAD1 FADH21 ADP1 ATPOxidative Phosphorylation

Membutuhkan koenzim sebagai pembawa H+ dan mengkonsumsi oksigenKey reactions take place in the electron transport system (ETS)Sitokrom dari ETS melewati elektron ke oksigen, membentuk airThe basic chemical reaction is: 2 H2 + O2 2 H2OOxidative Phosphorylation and the Electron Transport SystemOxidation and Electron TransportOksidasi nutrisi melepaskan energi yang tersimpanmendonorkan elektron disertai dengan H +Electrons transferred to co-substrate

NAD+ + 2H+ + 2e- NADH + H+ FAD + 2H+ + 2e- FADH2

So, What Goes to the ETS???From each molecule of glucose entering glycolysis:From glycolysis: 2 NADHFrom the TCA preparation step (pyruvate to acetyl-CoA): 2 NADHFrom TCA cycle (TCA) : 6 NADH and 2 FADH2

TOTAL: 10 NADH + 2 FADH2Electron Transport ChainNADH + H+ and FADH2 enter ETCPerjalanan melalui kompleks I - IVH + mengalir melalui ETC dan akhirnya menempel pada O2 membentuk airNADH + H+ 3 ATPFADH2 2 ATPElectron Transport Chain

Glucose UtilizationGlucosePyruvateRibose-5-phosphateGlycogenEnergy StoresPentose Phosphate PathwayGlycolysisAdiposePentose Phosphate PathwaySecondary metabolism of glucoseProduces NADPHSimilar to NADHRequired for fatty acid synthesisGenerates essential pentosesRiboseUsed for synthesis of nucleic acidsPentose Phosphate PathwayGlucose-6-phosphate6-Phospho- glucono-lactone6-Phospho- gluconateD-Ribulose-5-phosphateD-Ribose- 5-phosphateRNA or DNAGlucose UtilizationGlucosePyruvateRibose-5-phosphateGlycogenEnergy StoresPentose Phosphate PathwayGlycolysisAdiposeEnergy StorageEnergi dari kelebihan karbohidrat (glukosa) disimpan sebagai lemak dalam jaringan adiposaAsetil-KoA (dari siklus TCA) didorong ke sintesis asam lemak pada saat kelebihan energiDitentukan oleh rasio ATP: ADPHigh ATP, acetyl-CoA goes to fatty acid synthesisLow ATP, acetyl CoA enters TCA cycle to generate MORE ATPFates of GlucoseFed stateStorage as glycogenLiverSkeletal muscleStorage as lipidsAdipose tissueFasted stateMetabolized for energyNew glucose synthesizedSynthesis and breakdown occur at all times regardless of state...

The relative rates of synthesis and breakdown changeGluconeogenesisNecessary processGlucose is an important fuelCentral nervous systemRed blood cellsNot simply a reversal of glycolysisInsulin and glucagon are primary regulatorsFasting SituationWhere does required glucose come from? Glycogenolysis

Lipolysis

Proteolysis

Kerusakan atau mobilisasi glikogen yang disimpan oleh glukagonGlukagon - hormon yang disekresi oleh pankreas selama masa puasa Mobilization of fat stores stimulated by glucagon and epinephrine Triglyceride = glycerol + 3 free fatty acids Glycerol can be used as a glucose precursor Pemecahan protein otot dengan pelepasan asam aminoAlanin dapat digunakan sebagai prekursor glukosa

Low Blood GlucoseProteins Broken DownInsulin: GlucagonPancreasMuscleAdipose CellsGlycogenGlycerol, fatty acids releasedGlucose releasedDalam keadaan berpuasa, substrat untuk sintesis glukosa (glukoneogenesis) dilepaskan dari "penyimpanan" ...Figure 22-7 (2 of 5)Fasted-State Metabolism

FASTED-STATE METABOLISMLiverglycogenstoresEnergyproductionEnergy productionGlucoseLiver glycogen becomes glucose.orGlycogenPyruvateLactateEnergy productionGlucoseGlycogenolysisGluconeogenesisCopyright 2007 Pearson Education, Inc., publishing as Benjamin Cummings63Gluconeogenesis Synthesis of glucose from non-carbohydrate precursors during fasting in monogastrics

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