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 - How 2 used many. 4 ATP Formed Glycolysis know Imp to many left how are molecules end at from the 18 glucose to pyruvate? Glycolysis ⑥ · Q ② ③ 19 GLYCOLYSIS - animations https://www.youtube.com/watch?v=8Kn6BVGqKd8 20 Chem 361 – Biochemistry 21 22 Dr. Salman Ashraf 23 (Gives 2 H28) &Final product 24 - Glycolysis - - Need to know structure Need to Need to know the know 10 steps the structure of pyruvate 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 (Can be inhibited by ATP) Fates of Pyruvate From Glycolysis O2 NO O2 yeast NO O2 - - - In human muscles Stress Muscle spasms 29 Fates of pyruvates  lactic acid No oxygen (anaerobic condition) in mammals – pyruvate is converted to lactic acid - - - Will not get energy Energy will Enzyme to lactate be reduced convert pyruvate to dehydrogenase 30 lactate is 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 - No oxygen present - No oxygen present 32 NAD+ Needs to be Recycled! (Quiz) (To Prevent Decrease in Oxidation Reactions) > - > - CO2 is No (O2 produced produced 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 (Catalyzes citrate to - ( < Coxi dative ( i (converts - 3 Citric Acid Cycle (Krebs Cycle) / ( L f (Oxidative rxn) Cannot be produced if there is a lack of Vitamin B1) Coxidative rxn) rxn) T (oxidative xn) 35 isocitrate First reaction of the Citric Acid Cycle (No need to learn structure) 36 Summary of the Citric Acid Cycle FADH2 (Amina to acid that combines give 3 ATP) Acetyl-CoA + 2H2O + 3NAD+ + FAD + GDP + Pi ↓ 2CO2 + 3NADH + 3H+ + HSCoA + FADH2 + GTP 37 Catabolism of 1 glucose molecule Glucose ↓ 2 ATP 2 Pyruvate 2 NADH (6 ATP) ↓ 2 NADH (6 ATP) 2 Acetyl-CoA ↓ 2 GTP Citric Acid Cycle 6 NADH (18 ATP) 2 FADH2 (4 ATP) ↓ CO2 4 ATP + 34 ATP = 38 ATP (In reality, 1 NADH produces ~ 2.5 ATP and 1 FADH2 produced ~ 1.5 ATP) 38 How does NADH and FADH2 give us ATP? ↓ Electron Transport Chain and Oxidative Phosphorylation Dr. Salman Ashraf 39 http://en.wikipedia.org/wiki/NADH Dr. Salman Ashraf 40 Electron Transport Chain 41 Table 14.1 Electron Transport Chain Table 14.1 Prentice Hall c2002 Chapter 14 29 Prentice Hall c2002 Chapter 14 29 42 Electron Transport Chain 43 Electron Transport Chain 44 Structure of ATP synthase 45 Electron Transport Chain 46 Overview of Electron Transport and Oxida5ve Phosphoryla5on http://www.brookscole.com/chemistry_d/templates/student_resources/shared_resources/ animations/oxidative/oxidativephosphorylation.html 47 Summary – ETC & OP  In mitochondria, electrons are passed down a series of electrontransfer complexes  As electrons are passed down, protons (H+) are transferred from the Matrix to the Inter-membrane space. Eventually causing a high [H +] in the Inter-membrane space relative to the Matrix – Proton Gradient is established. These H+ are then allowed to come back to the Matrix through ATP Synthetase Complex, which uses the energy from the movement of H+ to convert ADP + Pi  ATP  A pair of electrons passes from NADH to O2 through Complexes I, III and IV   Enough protons pumped to make 2.5 ATP (or 3 ATP) A pair of electrons passes from FADH2 to O2 through Complexes II, III and IV  Enough protons pumped to make 1.5 ATP (or 2 ATP) 48 49 50 Dr. Salman Ashraf Chem 361 – Biochemistry 51 Regulation of Glycolysis : allosteric and transcription control https://www.youtube.com/watch?v=6qvIPMzS_iY