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D R . N U R A I Z A M E U T I A , M . B I O M E DD R . E K A R O I N A M E G A W A T I , M . K E S

DEPT. FISIOLOGI ,2012FAKULTAS KEDOKTERAN USU

INTRODUCTION TO

METABOLISM

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Metabolism

Metabolism : all chemical reactions necessary tomaintain life

Anabolic reactions : synthesis of larger moleculesfrom smaller ones

Catabolic reactions : hydrolysis of complexstructures into simpler ones

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

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Cellular respiration : food fuels are broken downwithin cells and some of the energy is captured toproduce ATP

Enzymes shift the high-energy phosphate groups ofATP to other molecules

These phosphorylated molecules are activated toperform cellular functions

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ATP functions : energy currency in metabolism

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Stages of Metabolism

1. Digestion : breakdown of food; nutrients aretransported to tissues

2. Anabolism and formation of catabolic intermediates

where nutrients are:Built into lipids, proteins, and glycogen

Broken down by catabolic pathways to pyruvic acidand acetyl CoA

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

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Stages ofMetabolism

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Metabolic Interactions

From a metabolic standpoint, the body is consider as5 components :

The liver

Adipose tissue

Skeletal muscle

Neural tissue

Other peripheral tissue

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

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The Absorptive and Postabsorptive States

Metabolic controls equalize blood concentrations ofnutrients between two states :

Absorptive The time during and shortly after nutrient intake

Postabsorptive The time when the GI tract is empty

Energy sources are supplied by the breakdown of bodyreserves

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Absorptive State

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Principal Pathways of the Absorptive State

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Postabsorptive State

The major metabolic thrust is catabolism andreplacement of fuels in the blood

Glucose is provided by glycogenolysis andgluconeogenesis

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 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 & GLUCAGONIN METABOLIC INTERACTION

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Regulation by other hormones

Absorptive State Postabsorptive state

Insulin

Growth HormonesAndrogensEstrogens

Glucagon

EpinephrineGlucocorticoids

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Referensi :

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. chapter22-Metabolism and Energy Balance.