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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.
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