INTRODUCTION TO METABOLISMdr. Nuraiza Meutia, M.Biomeddr. Eka Roina Megawati, M.Kes

Dept. Fisiologi ,2011Fakultas Kedokteran USUReferensi :Guyton & Hall. Textbook of Medical Physiology. 11th ed. Elsevier Saunders.2006. pp 865-888.Marieb EN. Human Anatomy and Physiology. 6th Ed. Pearson Educ.2004. chapter 24-Nutrition,Metabolism and Body Temp.Regulation.Martini FH. Fundamentals of Anatomy and Physiology, 6th Ed. Pearson Educ.2004. chapter 25-Metabolism and Energetic.Silverthorn DU. Human Physiology an Integrated Approach. 3rd Ed. Pearson Educ.2004. chapter 22-Metabolism and Energy Balance.

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MetabolismMetabolism : all chemical reactions necessary to maintain life

Anabolic reactions : synthesis of larger molecules from smaller ones

Catabolic reactions : hydrolysis of complex structures into simpler ones

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The nutrient pool is the source of the substrates for both catabolism and anabolism.

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Cellular respiration : food fuels are broken down within cells and some of the energy is captured to produce ATP

Enzymes shift the high-energy phosphate groups of ATP to other molecules

These phosphorylated molecules are activated to perform cellular functions

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ATP functions : energy currency in metabolism

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Stages of Metabolism1. Digestion : breakdown of food; nutrients are transported to tissues

2. Anabolism and formation of catabolic intermediates where nutrients are:Built into lipids, proteins, and glycogenBroken down by catabolic pathways to pyruvic acid and acetyl CoA

3. Oxidative breakdown : nutrients are catabolized to carbon dioxide, water, and ATP

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Stages of Metabolism

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Metabolic InteractionsFrom a metabolic standpoint, the body is consider as 5 components :The liverAdipose tissueSkeletal muscleNeural tissueOther peripheral tissue

The 5 components shows different patterns of metabolic activity during 24-h period

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The Absorptive and Postabsorptive StatesMetabolic controls equalize blood concentrations of nutrients between two states :

AbsorptiveThe time during and shortly after nutrient intakePostabsorptiveThe time when the GI tract is empty Energy sources are supplied by the breakdown of body reserves

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Absorptive StateThe major metabolic thrust is anabolism and energy storageDietary glucose is the major energy fuelExcess amino acids are deaminated and used for energy or stored as fat in the liver

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Absorptive State

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Principal Pathways of the Absorptive StateIn muscle:Amino acids become proteinGlucose is converted to glycogenIn the liver:Amino acids become protein or are deaminated to keto acidsGlucose is stored as glycogen or converted to fatIn adipose tissue:Glucose and fats are converted and stored as fatAll tissues use glucose to synthesize ATP

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Principal Pathways of the Absorptive State

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Postabsorptive StateThe major metabolic thrust is catabolism and replacement of fuels in the blood

Glucose is provided by glycogenolysis and gluconeogenesis

Fatty acids and ketones are the major energy fuels

Amino acids are converted to glucose in the liver

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Postabsorptive State

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Principle Pathways in the Postabsorptive StateIn muscle:Protein is broken down to amino acids Glycogen is converted to ATP and pyruvic acid (lactic acid in anaerobic states)In the liver:Amino acids, pyruvic acid, stored glycogen, and fat are converted into glucoseFat is converted into keto acids that are used to make ATPFatty acids (from adipose tissue) and ketone bodies (from the liver) are used in most tissue to make ATPGlucose from the liver is used by the nervous system to generate ATP

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Principle Pathways in the Postabsorptive State

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Fasted State or Post-Absorptive Metabolism: Catabolic

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Regulation of Reversible pathways

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DOMINATION OF INSULIN & GLUCAGON IN METABOLIC INTERACTION

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Regulation by other hormones

Absorptive StatePostabsorptive stateInsulinGrowth HormonesAndrogensEstrogens Glucagon EpinephrineGlucocorticoids

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