Y khoa, dược - Spotlight on metabolism and energy balance

Pathways initiate breakdown of macronutrients Anaerobic Breakdown glucose Do not require oxygen Aerobic Breakdown glucose, fat, and protein Require oxygen

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Spotlight on Metabolism and Energy BalanceEnergy: Fuel for WorkEnergy sourceChemical energy in carbohydrates, fat, and proteinTransferring food energy to cellular energyStage 1: digestion, absorption, and transportStage 2: breakdown of molecules Stage 3: transfer of energy to a form cells can useWhat Is Metabolism?CatabolismReactions that break down compounds into small unitsAnabolismReactions that build complex molecules from smaller onesWhat Is Metabolism?Cell is the metabolic processing centerNucleusCytoplasm: cytosol + organellesMitochondria are the source of many energy pathwaysWhat Is Metabolism?Who are the key energy players?ATP is the body’s energy currencyATP = adenosine triphosphateForm of energy cell useNAD and FAD: transport shuttlesAccept high-energy electrons for use in ATP productionBreakdown and Release of EnergyPathways initiate breakdown of macronutrientsAnaerobicBreakdown glucoseDo not require oxygenAerobicBreakdown glucose, fat, and proteinRequire oxygenBreakdown and Release of EnergyExtracting energy from carbohydrateGlycolysisPathway splits glucose into two pyruvatesTransfers electrons to NADProduces some ATPBreakdown and Release of EnergyExtracting energy from carbohydratePyruvate to acetyl CoAReleases CO2Transfers electrons to NADBreakdown and Release of EnergyExtracting energy from carbohydrateCitric acid cycleReleases CO2Produces GTP (like ATP)Transfers electrons to NAD and FADBreakdown and Release of EnergyExtracting energy from carbohydrateElectron transport chainAccepts electrons from NAD and FADProduces large amounts of ATPProduces waterEnd products of glucose catabolismATP, H2O, and CO2Breakdown and Release of EnergyExtracting energy from fatSplit triglycerides into glycerol and fatty acidsTakes place in mitochondriaBeta-oxidationBreaks apart fatty acids into acetyl CoATransfers electrons to NAD and FADBreakdown and Release of EnergyExtracting energy from fatCompleting fatty acid breakdownAcetyl CoA from beta-oxidation enters cycleCitric acid cycle and electron transport chainFat burns in a flame of carbohydrateEnd products of fat breakdownATP, H2O, and CO2Breakdown and Release of EnergyExtracting energy from proteinSplit protein into amino acidsSplit off amino groupConverted to urea for excretionCarbon skeleton enters breakdown pathwaysEnd productsATP, H2O, CO2, ureaBiosynthesis and StorageMaking carbohydrate (glucose)GluconeogenesisUses pyruvate, lactate, glycerol, and certain amino acidsStoring carbohydrate (glucose  glycogen)Liver and muscle make glycogen from glucoseMaking fat (fatty acids)LipogenesisUses acetyl CoA from fat, amino acids, and glucoseStoring fat (triglyceride)Stored in adipose tissueBiosynthesis and StorageMaking ketone bodies (ketogenesis)Made from acetyl CoAWhen inadequate glucose in cellsMaking protein (amino acids)Amino acid pool supplied from Diet, protein breakdown, and cell synthesisBiosynthesisDifferent pathways used to build amino acids from carbon skeletonsSpecial StatesFeastingExcess energy intake from carbohydrate, fat, proteinPromotes storageFat  adipose tissueAmino acids  protein synthesisCarbohydrate  adipose tissueSpecial StatesFastingInadequate energy intakePromotes breakdownProlonged fastingProtects body protein as long as possibleSpecial StatesFastingSurvival priorities and potential energy sourcesPreserve glucose-dependent tissueRBC, brain cells, central nervous systemMaintain muscle massSpecial StatesFastingThe prolonged fast: In the beginningBlood glucose drops, liver breaks down glycogen to glucoseGluconeogenesisFat and protein are primary fuelSpecial StatesFastingThe early weeksSeveral energy-conservation strategiesSeveral weeks of fastingRely on stored body fatThe end is nearMuscle atrophy and emaciationSacrificed muscle tissue in attempt to preserve brain tissueEnergy BalanceEnergy intake vs. energy outputEnergy equilibriumIntake = outputMaintain weightEnergy BalancePositive energy balanceIntake > outputGain weightNegative energy balanceIntake < outputLose weightEnergy InRegulation of intakeInternal cuesHungerPrompts eatingSatiationSignals to stop eatingSatietyTells when you are ready to eat againEnergy InRegulation of intake External cuesAppetitePsychological desire to eatInfluenced by the eating environmentEnergy InControl by committeeWhat stimulates our cues?Internal, physiological responseEating environmentEnergy InInternal factorsGastrointestinal sensationsSense of fullnessNeurological and hormonal factorsNeuropeptide YGhrelinLeptinEnergy InExternal factorsDiet compositionEnergy density, balance of energy sources, and formMacronutrientsSensory propertiesTasteEnergy InExternal factorsPortion sizeSuper-size cultureEnvironment and social factorsHypothalamusEmotional factorsHypothalamusEnergy Out: Fuel UsesTotal energy expenditureMajor components of energy expenditureEnergy expenditure at rest (basal energy expenditure)Energy for basic body functionsAffected by body size, composition, age, and genderEnergy Out: Fuel UsesMajor components of energy expenditurePhysical activityHighly variableAffected by body size, fitness level, type of activityThermic effect of food (TEF)Energy to digest, absorb, metabolize foodEnergy Out: Fuel UsesEstimating total energy expenditureResting energy expenditure (REE)1.0 kcal/kg/hr for males0.9 kcal/kg/hr for femalesPhysical activityAdd a % of REE (see Table 8.2)Thermic effect of food6% to 10% of (REE + physical activity)Estimating Energy ExpenditureEstimated Energy Requirement (EER)Equations for males and femalesFactors for age, weight, height, and physical activityPredicts total energy expenditure (TEE)Body CompositionBody compositionFat and lean muscle massAssessing body weightBody mass index (BMI)Weight (kg) × height2 (m)BMI ≤ 18.5 kg/m2 = underweightBMI 18.5 to ≥ 25 kg/m2 = normal weightBMI 25 to ≤ 30kg/m2 = overweightBMI ≥ 30 kg/m2 = obeseBody CompositionAssessing body fatnessDXAUnderwater weighingBodPodSkinfold measurementsBioelectrical impedanceBody CompositionBody fat distributionGynoid obesity (“pear”)Excess fat in hips and thighsAndroid obesity (“apple”)Excess fat around abdomenWaist circumference

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