Carbohydrates Metabolism Lecture 4 PDF

Carbohydrates Metabolism College of Health and Medical Techniques Department of Anesthesiology 1st Grade https://sawauniversity.edu.iq 6074 Lecture 4 Dr. Dheyaa Yahaia Aziz Alha...

Carbohydrates Metabolism College of Health and Medical Techniques Department of Anesthesiology 1st Grade https://sawauniversity.edu.iq 6074 Lecture 4 Dr. Dheyaa Yahaia Aziz Alhameedi Carbohydrates  Carbohydrates are the most abundant organic molecules in nature. They have a wide range of functions:  Calories providing.  Energy storage, and  Serving as cell membrane components. Carbohydrates also serve as a structural component of many organisms, including  The cell walls of bacteria,  the exoskeleton of many insects,  and the fibrous cellulose of plants.  Carbohydrate metabolism  In Lecture two, individual enzymic reactions were analyzed to explain the mechanisms of catalysis.  However, in cells, these reactions rarely occur in isolation, but rather are organized into multistep sequences called pathways, such as that of glycolysis.  In a pathway, the product of one reaction serves as the substrate of the subsequent reaction.  Different pathways can also forming an integrated network of chemical reactions. These are collectively called Metabolism Carbohydrate metabolism  Metabolism, is the sum of all the chemical changes occurring in a cell, a tissue, or the body.  Most pathways can be classified as either  Catabolic (degradative) or  Anabolic (synthetic)  Catabolic reactions are break down complex molecules, such as proteins, polysaccharides, and lipids, to a few simple molecules, for example, CO₂, NH₃ (ammonia), and water.  Anabolic reactions are formation complex end products from simple precursors, for example, the synthesis of the polysaccharide, glycogen, from glucose. Q/ Define Metabolism? Q/ What the types of the metabolism? Q/If the reaction break down complex molecules called …………, whereas if the reaction form complex molecules called …………? Catabolic pathways  The function of catabolic pathways  Serve to capture chemical energy in the form of adenosine triphosphate (ATP).  Converted the molecules in the diet to building blocks needed for the synthesis of complex molecules.  Energy generation by degradation of complex molecules occurs in three stages. Q/ what the functions of Catabolic pathways Catabolic pathways Q/ Explain the stages of catabolic pathways? Anabolic pathways  Anabolic reactions combine small molecules, such as amino acids, to form complex molecules, such as proteins.  Anabolic reactions require energy (are endergonic), which is generally provided by the breakdown of ATP to adenosine diphosphate (ADP) and inorganic Phosphate (P). Q/ What the function of Anabolic reactions? Q/ Is anabolic reactions require energy or donate energy? Q/ By scheme, Compare the catabolic and anabolic pathways. Aerobic and anaerobic oxidation of glucose  In the presence of oxygen (aerobic conditions), most animal cells are capable of “respiring” various types of nutrient (lipids, amino acids, and carbohydrates), using oxidative processes to break them down completely.  If oxygen is lacking (anaerobic conditions), only glucose can be used for ATP synthesis. Q/What type of oxidative presses of glucose? Glycolysis  Glycolysis (from the Greek glykys, meaning “sweet,” and lysis, meaning “splitting”).  Glycolysis is the sequence processes in which a molecule of glucose is degraded in a series of enzyme-catalyzed reactions to yield two molecules of the three-carbon compound pyruvate.  During the glycolysis, some of the free energy released from glucose is conserved in the form of ATP and NADH.  Glycolysis is an catabolism.  The glycolytic breakdown of glucose is the sole source of metabolic energy in some mammalian tissues and cell types.  Fermentation is a general term for the anaerobic degradation of glucose or other organic nutrients to obtain energy, conserved as ATP. Q/Define glycolysis? Q/ What the final compound produce from Glycolysis? Q/ What the Fermentation? Glycolysis has two phases  The breakdown of the six-carbon glucose into two molecules of the three-carbon pyruvate occurs in ten steps.  The first five of which constitute the preparatory phase  The second five steps called payoff phase Q/ Two phases of glycolysis are ……... and ……….? Preparatory phase Name of reaction Enzyme used 1. Phosphorylation of glucose Hexokinase Q/ Explain the phosphorylation reaction of glucose? Preparatory phase Name of reaction Enzyme used 2. Isomerization of glucose 6-phosphate phosphoglucose isomerase Q/ Explain the isomerization of glucose 6-phosphate reaction Preparatory phase Name of reaction Enzyme used 3. Phosphorylation of fructose 6-phosphate phosphofructokinase-1 Q/ Explain the phosphorylation of fructose 6-phosphate reaction Preparatory phase Name of reaction Enzyme used 4. Cleavage of fructose 1,6-bisphosphate Aldolase Q/ Explain the Cleavage of fructose 1,6-bisphosphate reaction Preparatory phase Name of reaction Enzyme used 5. Isomerization of dihydroxyacetone phosphate Triose phosphate isomerase Q/ Explain the Isomerization of dihydroxyacetone phosphate reaction Payoff phase Name of reaction Enzyme used 6. Oxidation of glyceraldehyde 3-phosphate Glyceraldehyde 3-phosphate dehydrogenase Q/ Explain the Oxidation of glyceraldehyde 3-phosphate reaction Payoff phase Name of reaction Enzyme used 7. Synthesis of 3-phosphoglycerate producing ATP Phosphoglycerate kinase Q/ Explain the Synthesis of 3-phosphoglycerate producing ATP reaction Payoff phase Name of reaction Enzyme used 8. Shift of the phosphate group from carbon 3 to carbon 2 Phosphoglycerate mutase Q/ Explain the Shift of the phosphate group from carbon 3 to carbon 2 reaction Payoff phase Name of reaction Enzyme used 9. Dehydration of 2-phosphoglycerate enolase Q/ Explain the Dehydration of 2-phosphoglycerate reaction Payoff phase Name of reaction Enzyme used 10. Formation of pyruvate Pyruvate kinase Q/ Explain the Formation of pyruvate reaction Q/Explain the first five (preparatory phase) steps in the glycolysis process? Q/Explain the second five ( payoff phase) steps in the glycolysis process? The final energy gain  In the preparatory phase there is two molecules of ATP is consumed by converting ATP to ADP in step 1 and 3.  In the payoff phase there is four molecules of ATP is generated by converting ADP to ATP, two in step 7 and two in step 10.  The final ATP formed is two.  Also two energetic molecules of NADH is formed in step6. Q/ How many ATP molecules are consumed in preparatory phase and where? Q/ How many ATP molecules are generated in payoff phase and where? Q/ How many NADH molecules are generated in payoff phase and where? Q/ How many the final ATP molecules are generated in glycolysis process? Fates of Pyruvate the pyruvate formed by glycolysis is further metabolized via one of three catabolic routes. The route 1  Under aerobic conditions, Pyruvate is oxidized, with loss of its carboxyl group as CO₂, to yield the acetyl group of acetyl-coenzyme A.  The acetyl group is then oxidized completely to CO₂ by the citric acid cycle.  The electrons from these oxidations are passed to O₂ through a chain of carriers in the mitochondrion, to form H₂O.  The energy from the electron-transfer reactions drives the synthesis of ATP in the mitochondrion. Q/ Explain the route 1 in the fates of pyruvate? Q/ Is the route 1 in the fates of pyruvate occurs under aerobic or anaerobic conditions? The route 2  The pyruvate is reduced to lactate via lactic acid fermentation.  This route occur under anaerobic conditions. The route 3  The pyruvate is converted into ethanol and CO₂, a process called ethanol fermentation.  This route occur under anaerobic conditions. Q/ The routes 2 and 3 in fates of pyruvate occur in ……. conditions? Q/ The routes 2 in fates of pyruvate called………..? Q/ The routes 3 in fates of pyruvate called………? Transport of glucose into cells Glucose cannot diffuse directly into cells, but enters by one of two transport mechanisms: 1. Na⁺ -independent facilitated diffusion transport. 2. Na⁺ -monosaccharide cotransporter system. Na ⁺ -independent facilitated diffusion transport  This system is achieve by a family of 14 glucose transporters in cell membranes.  They are designated GLUT-1 to GLUT-14 These transporters exist in the membrane in two conformational states.  Extra cellular glucose binds to the transporter, which then alters its conformation, transporting glucose across the cell membrane. Q/ what the types of transport system of glucose into cell? Q/ Explain how glycose diffuse into cells, by Na⁺ -independent facilitated diffusion transport mechanism? Na⁺-monosaccharide cotransporter system  This is an energy-requiring process that transports glucose “against” a concentration gradient—that is, from low glucose concentrations outside the cell to higher concentrations within the cell.  This system is a carrier-mediated process in which the movement of glucose is coupled to the concentration gradient of Na⁺, which is transported into the cell at the same time.  The carrier is a sodium-dependent glucose transporter or SGLT. Q/ What the mechanism of glucose transported into cell which require energy? Q/ Why Na⁺-monosaccharide cotransporter system require energy? Pyruvate kinase deficiency  The normal, mature erythrocyte lacks mitochondria and is, therefore, completely dependent on glycolysis for production of ATP.  This high-energy compound is required to meet the metabolic needs of the red blood cell.  Pyruvate kinase deficiency will lead to reduced rate of glycolysis, leading to decreased ATP production.  The resulting alterations in the red blood cell membrane lead to changes in the shape of the cell and to death and lysis of red blood cells  That will lead to hemolytic anemia. Q/ What is the effect of pyruvate kinase deficiency? Lactic acidosis  Elevated concentrations of lactate in the plasma, termed lactic acidosis, occur when there is a collapse of the circulatory system.  The failure to bring enough amounts of oxygen to the tissues results in impaired oxidative phosphorylation and decreased ATP synthesis.  Therefore, the cells use anaerobic glycolysis as a backup system for generating ATP, producing lactic acid as the end product.  The excess oxygen required to recover is termed the oxygen debt.  The oxygen debt is often related to patient morbidity or mortality. In many clinical situations, measuring the blood levels of lactic acid allows the rapid, early detection of oxygen debt in patients and the monitoring of their recovery. Q/ Why does lactic acidosis occur? Q/ How does a cell generate ATP when there is not enough oxygen to be brought into the tissues? Scan to get the lecture