Intermediary Metabolism CHEM 141 PDF

Unit I Intermediary Metabolism CHEM 141: Biochemistry II 1 KFL 2025 Topic Outline A. Metabolism D. Digestion Processes B. Metabolic Diversity Salivary Classification based on: Ga...

Unit I Intermediary Metabolism CHEM 141: Biochemistry II 1 KFL 2025 Topic Outline A. Metabolism D. Digestion Processes B. Metabolic Diversity Salivary Classification based on: Gastric Carbon requirement Intestinal Energy source Digestive Enzymes Oxygen need E. Catabolic Stages C. Metabolic Maps F. Metabolic Balance Multienzyme systems D. Metabolic Processes Catabolism Anabolism 2 Overview of Metabolism Metabolism is the sum of catabolic and anabolic biochemical reactions. 3 METABOLISM represents the sum of the chemical changes that convert nutrients, the “raw materials” necessary to nourish living organisms, into energy and the cells' chemically complex finished products. transformation of substrates into end products through many specific chemical intermediates, referred to as intermediary metabolism. 4 5 Metabolic Diversity 6 Metabolic Diversity Classification based on carbon requirements: o Autotrophs – uses carbon dioxide only o Heterotrophs – requires organic form of carbon (e.g., glucose) Classification based on energy sources: o Phototrophs – photosynthetic organisms, uses light o Chemotrophs – energy extraction through redox reactions of organic compounds (e.g., glucose, Fe2+, NO2-, NH4+, elemental sulfur) 7 Metabolic Diversity 8 Metabolic Diversity Classification based on O2 requirement: o Aerobes – uses oxygen as an electron acceptor in energy-producing metabolic pathways ▪ obligate aerobes – organisms for which O2 is obligatory for life o Anaerobes – can subsist without O2 ▪ facultative anaerobes – species that can adapt to anaerobic conditions (e.g., E. coli) ▪ obligate anaerobes – cannot use oxygen at all and are even poisoned by it (e.g., C. botulinum) 9  Metabolic Diversity Life involves a constant flow of matter and energy among living organisms. The flow of matter is cyclical. 1 0 Metabolic Maps 1 1 Metabolic Maps (c) Multifunctional protein-centric (a) Metabolite-centric (b) Protein-centric 1 2 Multi-enzyme systems (A) Separate enzymes (B) Multienzyme complex (C) Membrane-bound multienzyme system 1 3 Metabolic Processes 1 4 Catabolism Energy-yielding metabolic process Involves the oxidative degradation of complex nutrient molecules (carbohydrates, lipids, and proteins) obtained from the environment or cellular reserves. 1 5 Anabolism Energy-requiring metabolic process A biosynthetic process in which the varied and complex biomolecules (proteins, nucleic acids, polysaccharides, and lipids) are assembled from simpler precursors. 1 6 Metabolic Pathways 1 7 Salivary Digestion most characteristic enzyme of saliva is α-amylase, or ptyalin, which breaks carbohydrates (starch) down to maltoses by cleaving the α1→4 glycosidic linkages also contains lingual lipase that initiates hydrolysis of dietary fat and mucins that lubricate the bolus 1 8 Gastric Digestion gastric mucosa secretes 1.2 – 2.5 L of gastric juice per day, which renders food particles to become more soluble and form chyme HCl is the chief component; low pH environment (pH 1.5 – 2.0) activates pepsinogen (zymogen) to form pepsin and be utilized for protein digestion 1 9  Intestinal Digestion primary function is to further digest food and absorb nutrients the duodenum is the segment of the small intestine that receives the pancreatic digestive enzymes (trypsin, chymotrypsin, etc.) and pancreatic bicarbonate and bile from the gallbladder 2 0 Digestive Enzymes 2 1 Gastric Digestion most characteristic enzyme of saliva is α-amylase, or ptyalin, which breaks carbohydrates (starch) down to maltoses by cleaving the α1→4 glycosidic linkages also contains lingual lipase that initiates hydrolysis of dietary fat and mucins that lubricate the bolus 2 2  Catabolic Stages aerobic catabolism produces CO2, H2O, NH3 as end products 2 3 Coordinated Metabolic Pathways maintaining a constant cellular environment requires complex metabolic regulation that coordinates the use of nutrient pools 2 4 Metabolic Balance 2 5