CHAPTER 24: Carbohydrate, Lipid, & Protein Metabolism General, Organic, & Biological Chemistry Janice Gorzynski Smith
CHAPTER 24: Carbohydrate, Lipid, & Protein Metabolism Learning Objectives: q Role in Metabolism of faby acid oxidadon, glycolysis, & Amino acid catabolism q ReacDons catalyzed by: kinase, isomerase, dehydrogenase, decarboxylase, carboxylase q Glycolysis: steps & net reacaon q Pyruvate conversion to acetyl Coenzyme A q Gluconeogenesis: steps in synthesis of glucose q Catabolism of Triacylglycerols: beta- oxidadon q Synthesis of ketone bodies: ketogenesis q Catabolism of Amino acids: q transaminadon & oxidadve deaminadon q Ketogenic vs glucogenic amino acid catabolism CH 24 Homework: End of Chapter problems: 30, 36, 38, 42, 47, 52, 58, 60, 64, 68, 71, 75, 76, 78, 80, 82, 96, 98 2
Metabolism Step 2 of Metabolism Fatty acid oxidation Glycolysis Amino Acid Catabolism à All lead to the production of Acetyl CoA 3
Metabolism Step 2 of Metabolism In the catabolism of carbohydrates, glycolysis converts glucose into pyruvate, which is then metabolized into acetyl CoA.
Metabolism Step 2 of Metabolism In the catabolism of lipids, fatty acids are converted into thioesters and then cleaved into many acetyl CoA units.
Metabolism Step 2 of Metabolism Amino acids are usually reassembled into new proteins. Since excess amino acids are not stored in the body, they can also be catabolized for energy. The amino groups (NH 2 ) are converted to urea [(NH 2 ) 2 C=O], which is excreted in urine.
Metabolism Step 2 of Metabolism: Urea Cycle hbp://www.t3portal.org/t3_portal_v1/!ssl!/webhelp/ales_vancura Catabolism_of_amino_acids.htm
Biochemical Rxns Common Enzymes 8
Biochemical Rxns Common Enzymes: Example The transfer of a phosphate unit from ATP to the fructose 6-phosphate molecule is catalyzed by a kinase enzyme. 9
Glycolysis Definition Glycolysis is a linear, 10-step anaerobic pathway that converts glucose into two molecules of pyruvate. Steps [1] [5] comprise the energy investment phase, where 2 ATP molecules are hydrolyzed. The 6-carbon glucose molecule is converted into two 3-carbon segments. Steps [6] [10] comprise the energygenerating phase, producing 1 NADH and 2 ATPs for each pyruvate formed. 10
Glycolysis Energy Investment 11
Glycolysis Energy Generation 12
Glycolysis Step 1 Step [1] begins with the phosphorylation of glucose into glucose 6-phosphate, using an ATP and a kinase enzyme. 13
Glycolysis Step 2 Step [2] isomerizes glucose 6-phosphate to fructose 6-phosphate with an isomerase enzyme. 14
Glycolysis Step 3 Step [3] is the phosphorylation of fructose 6-phosphate into fructose 1,6-bisphosphate with a kinase enzyme. Steps [1-3] add 2 phosphate groups and isomerize a 6- membered ring into a 5- membered ring. Energy is stored as 2 ATP molecules. 15
Glycolysis Step 4 Step [4] cleaves the fructose ring into a dihydroxyacetone phosphate and a glyceraldehyde 3-phosphate. 16
Glycolysis Step 5 Step [5] isomerizes the dihydroxyacetone phosphate into another glyceraldehyde 3-phosphate. Thus, the first phase of glycolysis converts glucose into 2 glyceraldehyde 3-phosphate units. 17
Glycolysis Step 6 In step [6] the aldehyde end of the molecule is oxidized and phosphorylated by a dehydrogenase enzyme and NAD + ; this produces 1,3-bisphosphoglycerate and NADH. 18
Glycolysis Step 7 In step [7], the phosphate group is transferred onto an ADP with a kinase enzyme, forming 3-phosphoglycerate and ATP. 19
Glycolysis Step 8 In step [8], the phosphate group is isomerized to a new position in 2-phosphoglycerate. 20
Glycolysis Step 9 In step [9], water is lost to form phosphoenolpyruvate. 21
Glycolysis Step 10 In step [10], the phosphate is transferred to an ADP, yielding pyruvate and ATP with a kinase enzyme. The 2 glyceraldehyde 3-phosphate units are converted into 2 pyruvate units in Phase two of glycolysis. Overall, the energy-generating phase forms 2 NADHs and 4 ATPs. 22
Glycolysis Overall Reaction 2 ATPs are used in phase one of glycolysis, and 4 ATPs are made in phase two of glycolysis. The net result is the synthesis of 2 ATPs from glycolysis The 2 NADHs formed are made in the cytoplasm and must be transported to the mitochondria to join the electron transport chain and make ATP. 23
Glycolysis Pyruvate Pyruvate can be converted into three possible products depending on the conditions and the organism. under aerobic conditions under anaerobic conditions in fermentation by microorganisms 24
Glycolysis ATP Yield 25
Glycolysis ATP Yield 2 x 2.5 ATP = 5 ATP 2 x 2.5 ATP = 5 ATP 2 ATP 6 x 2.5 = 15 ATP 2 x 1.5 = 3 ATP 26
Gluconeogenesis Definition Gluconeogenesis is the synthesis of glucose from noncarbohydrate sources lactate, amino acids, or glycerol. Gluconeogenesis is an anabolic pathway since it results in the synthesis of larger molecules from smaller ones. 27
Gluconeogenesis Cori Cycle 28