Week 3 Lecture Notes on Metabolism PDF

2023-09-26 Learning Objectives 1. Define metabolism and understand what it is. 2. Describe the process of glycolysis and understand how we represent metabolic reactions using net reactions. 3. Describe four general characteristics of all metabolic pathways and three objectives of metabolism. BNUR...

2023-09-26 Learning Objectives 1. Define metabolism and understand what it is. 2. Describe the process of glycolysis and understand how we represent metabolic reactions using net reactions. 3. Describe four general characteristics of all metabolic pathways and three objectives of metabolism. BNUR 2003 4. For each of the major metabolic pathways, state the startingsubstrate(s), end-product(s), cellular localization, category (anabolic/catabolic) and organ specialization. 2-4 Metabolism and Metabolic Regulation I 1 2 Cellular Metabolism Cellular Metabolism - Energy Metabolism Chemical tasks of maintaining essential cellular functions Anabolism Energy using Catabolism Energy releasing Adenosine Triphosphate (ATP) •Primary cellular fuel for survival •Created from the chemical energy contained within organic molecules •Used in synthesis of organic molecules, muscle contraction, and active transport •Stores and transfers_______________ Anabolism + Catabolism = _________________ 3 4 1 2023-09-26 Cellular Metabolism - Energy Digestion Extracellular breakdown of proteins, fats, polysaccharides into subunits Glycolysis Intracellular breakdown of subunits to pyruvate, then to _________________ Cellular Metabolism - Energy Citric acid cycle • Also called Krebs cycle or the tricarboxylic acid cycle (TCA) • LOTS of ATP produced via oxidative phosphorylation (needs oxygen to be present) • Waste products excreted 5 6 Cellular Metabolism - Energy Cellular Metabolism - Energy Oxidative phosphorylation • Occurs in the _________________ • Mechanism of producing energy from fats, CHO, proteins • Proceeds through series of transfer reactions Involves the removal or transfer of electrons from various intermediates via a coenzyme (i.e., nicotinamide adenine dinucleotide (NAD)) Anaerobic glycolysis • If oxygen is unavailable, CHO (glucose) is converted to pyruvic acid (pyruvate) in cytoplasm • Only produce 2 ATP molecules (insufficient for energy needs) • Pyruvate then converted to lactic acid • Process reverses when oxygen becomes available • lactic acid is converted back to either pyruvic acid or glucose, which moves into the mitochondria and enters the citric acid cycle 7 8 2 2023-09-26 Metabolism Cellular Metabolism - Energy Pyruvate is derived from the breakdown of glucose during glycolysis (cytoplasm) What is metabolism? • Within an organism, hundreds or thousands of chemical reactions are occurring simultaneously. Pyruvate is converted into Acetyl Coa. This process yields a small amount of ATP and NADH (which carry high-energy electrons for use in the ETC) • These reactions are carried out by an integrated network of pathways/processes. Some are anabolic, some are catabolic. Acetyl CoA feeds into the citric acid cycle. This generates some ATP, more energy carriers (NADH, FADH2), and CO2 (Mitochondrial matrix) • These pathways are collectively known as metabolism. 9 10 Metabolism Metabolism is complicated!!! ‘98 In order to understand disease, it is useful to know what metabolic systems should do: • Provide warmth and energy for living • Supply raw materials for tissue growth and repair • Compensate for variations in food intake • Respond in an effective and appropriate manner to injury and disease 11 12 3 2023-09-26 Metabolism is complicated!!! ‘11 Metabolism is complicated!!! ‘22 Anything you want to know about a metabolite can be found in large metabolomic databases https://hmdb.ca/ 13 14 Metabolism Metabolism The sum of the chemical reactions in an organism. _________ provides energy and building blocks for anabolism. 15 ___________uses energy and building blocks to build large molecules 16 4 2023-09-26 Metabolism Metabolism • In this course, we will learn the net reactions of several important pathways. A net reaction is the summation of all the reactions that are linked in a pathway. • The net reaction makes clear the unique biochemical role of each pathway. What is glycolysis? 17 18 Introduction to Glycolysis What is glycolysis? • Glycolysis breaks down glucose to form two molecules of pyruvate and two molecules of ATP. Introduction to Glycolysis Glycolysis – details! • Fortunately, we can represent glycolysis with a net reaction Glucose + 2 Pi + 2ADP + 2NAD+ 2 pyruvate + 2 ATP +2NADH + 2H+ + 2H2O 19 20 5 2023-09-26 Metabolism: Characteristics and Objectives There are four general characteristics of metabolic pathways: 1. Metabolic pathways are _____________________ • Reactions generally go to completion.This provides the pathway with direction. 2. Every metabolic pathway has a first committed step • Early in each pathway there is an irreversible reaction that commits the intermediate metabolite it produces to continue down the pathway. Metabolism: Characteristics and Objectives There are four general characteristics of metabolic pathways: 3. All metabolic pathways are regulated • Each pathway has a _______________reaction that is regulated in order to control the movement of metabolites through the metabolic pathway. 4. Metabolic pathways occur in specific cellular locations • This means that transport between the site of synthesis and the site of use is important. • E.g., most ATP is synthesized in mitochondria but used in cytoplasm. 21 22 Metabolism: Characteristics and Objectives Important Metabolic Pathways What are the major objectives of metabolic pathways? 1. Glycolysis converts glucose into pyruvate or lactate in the cytoplasm and is catabolic. 1. To produce ATP • Used to build complex molecules, contract muscles, generate electricity in nerves, power transport, etc. 2. Gluconeogenesis converts lactate and some amino acids to glucose in the cytoplasm and is anabolic. Most often occurs in the liver. 2. To produce oxidizing and reducing compounds that are capable of accepting or donating electrons during redox reactions. 3. Glycogenolysis converts glycogen to glucose in the cytoplasm and is catabolic. Occurs in the liver and in muscle. 4. Glycogenesis converts glucose to glycogen in the cytoplasm and is anabolic. Occurs in the liver, kidney and in muscle. 3. To produce building blocks for biosynthesis. 23 24 6 2023-09-26 Important Metabolic Pathways 5. The krebs/citric acid cycle and oxidative phosphorylation (electron transport chain) convert pyruvate and acetyl CoA into carbon dioxide and water in mitochondria and are catabolic. Exercise Download the “Metabolic Pathways Diagram” PDF on Blackboard. Fill in the missing pathways #’s to create a synthetic diagram that summarizes how these major metabolic reactions are interrelated: • • • • • • • • • 6. Lipolysis converts lipids to fatty acid and glycerol in the cytoplasm and is catabolic. Most often occurs in adipose tissue. 7. Lipogenesis converts acetyl CoA to lipids in the cytoplasm and is anabolic. Most often occurs in the adipose tissue. 8. Fatty acid oxidation converts fatty acids to acetyl CoA in mitochondria and is catabolic. 25 Glycolysis Gluconeogenesis Glycogenolysis Glycogenesis Citric acid cycle Oxidative phosphorylation (ETC) Fatty acid synthesis Lipolysis Fatty acid oxidation 26 There is also a fill-in-the-blank memory exercise posted 27 7