Chapter 17 - Glycolysis, Citric Acid Cycle, ETC & OP

CHAPTER 17: GLYCOLYSIS Week 12 CHEM311 Glucose Metabolism And Citric Acid Cycle (& Oxidative Phosphorylation) Metabolism = Catabolism + Anabolism Metabolism: Sum of ALL reactions in a cell Catabolism: Breaking down macromolecules to produce ENERGY Anabolism: Using ENERGY to make macromolecules ATP:...

CHAPTER 17: GLYCOLYSIS Week 12 CHEM311 Glucose Metabolism And Citric Acid Cycle (& Oxidative Phosphorylation) Metabolism = Catabolism + Anabolism Metabolism: Sum of ALL reactions in a cell Catabolism: Breaking down macromolecules to produce ENERGY Anabolism: Using ENERGY to make macromolecules ATP: The Cellular Energy Currency Catabolism – The degradation of fuel molecules which provides energy for cellular energy-requiring functions Cells use an energy conversion strategy that oxidizes glucose Small amounts of energy are released at several points in this pathway This energy is harvested and stored in bonds of ATP ATP = universal energy currency OR adenosine triphosphate 4 The Types of Cellular Work That Require Energy 5 ATP: The Molecule ATP is a nucleotide, a molecule composed of: Nitrogenous base 5-carbon sugar One, two, or three phosphoryl groups Phosphoester bond joins the first phosphoryl group to the 5-carbon sugar ribose Second and third groups are joined by phosphoanhydride bonds = high-energy bonds Major catabolic pathways in cell Sequence of metabolic reactions are called “pathways” e.g. boxidation pathway Glycolysis is the pathway that breaks down glucose to produce energy - ATP 7 Dr. Salman Ashraf Chem 361 – Biochemistry 8 Dr. Salman Ashraf Chem 361 – Biochemistry 9 Overview of Catabolic Processes Carbohydrates, fats, and proteins can be degraded to release energy Carbohydrates are the most readily used energy source Stage I: Hydrolysis of Dietary Macromolecules into Small Subunits The purpose of Stage I in catabolism is to degrade food molecules into component subunits: Polysaccharides degraded to monosaccharides Begins in the mouth with amylase action on starch Continues in small intestine with pancreatic amylase to form monosaccharides Proteins digested to amino acids Begins in the stomach with acid hydrolysis Serine proteases act in the small intestine Fats broken into fatty acids and glycerol Begins in small intestine with fat globules Disperse with bile salts Degrade with pancreatic lipase 11 Stage 2: Conversion of Monomers to a Form That Can Be Completely Oxidized Assimilate the small subunits into the pathways of energy metabolism – “usually make Acetyl CoA”. 12 Stage 3: Complete Oxidation of Nutrients and the Production of ATP Acetyl CoA carries acetyl groups, 2-carbon remnants of the nutrients Acetyl CoA enters the citric acid cycle Electrons and hydrogen atoms are harvested Acetyl group is oxidized to produce CO2 Electrons and hydrogen atoms harvested are used to produce ATP during oxidative phosphorylation 13 Overview of Catabolic Processes Carbohydrates, fats, and proteins can be degraded to release energy Carbohydrates are the most readily used energy source Glycolysis An extremely important catabolic pathway that breaks down GLUCOSE to produce ENERGY (ATP) 15 Summary The Overall Pathway of Glycolysis Conversion of Six-Carbon Glucose to Three-Carbon Glyceraldehyde-3-Phosphate Glyceraldehyde-3-Phosphate Is Converted to Pyruvate Control of Glycolysis The Overall Pathway of Glycolysis Glycolysis is the first stage of glucose metabolism One molecule of glucose is converted to fructose-1,6bisphosphate, which gives rise to two molecules of pyruvate It plays a key role in the way organisms extract energy from nutrients Once pyruvate is formed, it has one of several fates Glycolysis 18 Glycolysis 19 GLYCOLYSIS - animations https://www.youtube.com/watch?v=8Kn6BVGqKd8 20 Chem 361 – Biochemistry 21 22 Dr. Salman Ashraf 23 24 Glycolysis 25 Summary of Glycolysis 26 GLYCOLYSIS - animations https://www.youtube.com/watch?v=PowpbzBaTM0 Control Points in Glycolysis Three reactions exhibit particularly large decreases in free energy; the enzymes that catalyze these reactions are sites of allosteric control Hexokinase Phosphofructokinase Pyruvate kinase Fates of Pyruvate From Glycolysis O2 NO O2 yeast NO O2 29 Fates of pyruvates  lactic acid No oxygen (anaerobic condition) in mammals – pyruvate is converted to lactic acid 30 Fates of pyruvates  ethanol No oxygen (anaerobic condition) in yeast – pyruvate is converted to acetaldyde and then to ethanol 31 Fates of Pyruvate From Glycolysis 32 NAD+ Needs to be Recycled! (To Prevent Decrease in Oxidation Reactions) 33 Fates of pyruvates  complete oxidation to CO2 + H2O In the presence of O2 – Aerobic conditions 1. Pyruvate gets transported to the mitochondria 2. Pyruvate gets converted to acetyl-CoA 3. Acetyl-CoA “enters” the Citric Acid cycle (Krebs Cycle) 34