* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Prolonged starvation
Survey
Document related concepts
Photosynthetic reaction centre wikipedia , lookup
Fatty acid synthesis wikipedia , lookup
Biochemical cascade wikipedia , lookup
Oxidative phosphorylation wikipedia , lookup
Evolution of metal ions in biological systems wikipedia , lookup
Adenosine triphosphate wikipedia , lookup
Basal metabolic rate wikipedia , lookup
Citric acid cycle wikipedia , lookup
Glyceroneogenesis wikipedia , lookup
Fatty acid metabolism wikipedia , lookup
Phosphorylation wikipedia , lookup
Transcript
BIOC 460 - DR. TISCHLER LECTURE 21 METABOLISM: BASIC CONCEPTS OBJECTIVES 1. Identify the three major forms in which energy is stored and the four primary circulating fuels. 2. Distinguish between G and G, and explain the relationship between mass action effect and G. 3. Define high-energy phosphate transfer potential, and explain its significance in terms of the formation of ATP via substrate-level phosphorylation. 4. Define the absorptive (well-fed), postabsorptive (fasting), starvation (gluconeogenic) and prolonged starvation nutritional states and identify the primary sources of glucose in each of these. GENERAL INFORMATION ABOUT METABOLISM Catabolism: breakdown of fuels – used to produce energy Anabolism: synthesis and storage of fuels Most cells use oxidative metabolism (varying degrees) Red blood cells lack mitochondria = entirely anaerobic ATP: most common direct energy source OVERVIEW OF METABOLIC PATHWAYS AND SYSTEMS OF ENERGY METABOLISM Nucleic Acids GLYCOGEN PROTEIN Ribose-5-P Glucose Lactate Glucose-6-P TRIACYLGLYCEROLS Urea Amino Acids Pyruvate Free Fatty Acids Acetyl-CoA Ketone Bodies ATP Figure 1. Energy systems PHYSIOLOGICAL FREE ENERGY G = G + 2.3 log [products/reactants] G = actual free energy difference of reaction in cell; must be negative for reaction to proceed G = point of reference "mass action effect" change G by altering ratio of products/substrates product and/or reactant lowers G reaction proceeds better towards product O O O PHOSPHOCREATINE ATP O * - P-O-P-O-POCH2 O Adenine O O- O - O- g b a -7.3 -6.6 - O- CPK OH OH NH P*N-C N CH2 COO O- CH3 -10.3 Kcal -14.8 O CH2 Kcal -10.1 O O O- P* O C O- OH O CH CH2 O P - O- O P *O C O- COO- O- 1,3-bisPHOSPHOGLYCERATE PHOSPHOENOLPYRUVATE (TWO HIGH ENERGY INTERMEDIATES OF THE GLYCOLYTIC PATHWAY) Figure 2. Structures of important compounds having high-energy phosphate bonds. ATP formed by substrate-level phosphorylation SUMMARY OF CARBOHYDRATE PATHWAYS GLYCOGEN Glycogenolysis Glycogenesis NADPH formation GLUCOSE Glucose-6-P PPP Nucleic acid synthesis Glycolysis Gluconeogenesis Acetyl CoA Pyruvate LACTATE anaerobic metabolism aerobic metabolism Citric Acid Cycle CO2 PPP = pentose phosphate pathway Figure 3. Summary of carbohydrate pathways. Pyruvate metabolism to acetyl CoA and carbon dioxide is irreversible. Table 1. Summary of Nutritional States Nutritional State Description period within no more than 4 hours after the last meal Absorptive commenced during which food is digested and absorbed; also called well-fed state Postabsorptive period after food is completely digested and absorbed up until 18 to 24 hours afterwards; also referred to as a fasting state Starvation period of time from about 24 hours after the last meal and onwards until refeeding or death; early starvation is approximately the first 5 days Prolonged starvation period of time one week and longer after food deprivation BLOOD GLUCOSE HOMEOSTASIS maintenance of blood glucose concentration brain depends on glucose; >50% of total prolonged starvation has <25% decline in glucose hyperglycemia – too little insulin hypoglycemia – too little intake or too much insulin Table 2. Primary sources and fates of glucose, and the major fuel for the brain in each phase Nutritional Absorptive status (Well-fed) Postabsorptive (Fasting) Early Starvation Liver gluconeogenesis Prolonged Starvation Sources of Blood Diet Glucose Liver glycogen Tissues Using Glucose (fates) All Primarily Brain and red brain and red blood cells blood cells Red blood cells only Primary Brain Fuel Glucose Glucose Ketone bodies Glucose Liver gluconeogenesis