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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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