DR. NURAIZA MEUTIA, M.BIOMEDDR. EKA ROINA MEGAWATI, M.KES

DEPT. FISIOLOGI ,2011FAKULTAS KEDOKTERAN USU

INTRODUCTION TO METABOLISM

Metabolism

Metabolism : 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

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

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

ATP functions : “energy currency” in metabolism

Stages of Metabolism

1. Digestion : breakdown of food; nutrients are transported 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 acid

and acetyl CoA

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

Stages of Metabolism

Metabolic Interactions

From a metabolic standpoint, the body is consider as 5 components : The liver Adipose tissue Skeletal muscle Neural tissue Other peripheral tissue

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

The Absorptive and Postabsorptive States

Metabolic controls equalize blood concentrations of nutrients 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

body reserves

Absorptive State

The major metabolic thrust is anabolism and energy storage

Dietary glucose is the major energy fuelExcess amino acids are deaminated and

used for energy or stored as fat in the liver

Absorptive State

Principal Pathways of the Absorptive State

Postabsorptive State

The 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

Postabsorptive State

Principle Pathways in the Postabsorptive State

“Fasted State” or Post-Absorptive Metabolism: Catabolic

Regulation of Reversible pathways

DOMINATION OF INSULIN & GLUCAGON IN METABOLIC INTERACTION

Regulation by other hormones

Absorptive State Postabsorptive state

InsulinGrowth HormonesAndrogensEstrogens

Glucagon EpinephrineGlucocorticoids

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.

chapter 22-Metabolism and Energy Balance.