CHAPTER 24: Carbohydrate, Lipid, & Protein Metabolism General, Organic, & Biological Chemistry...

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CHAPTER 24: Carbohydrate, Lipid, & Protein Metabolism

General, Organic, & Biological ChemistryJanice Gorzynski Smith

Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.

CHAPTER 24: Carbohydrate, Lipid, & Protein Metabolism

Learning Objectives: Role in Metabolism of fatty acid oxidation, glycolysis, & Amino acid

catabolism Reactions catalyzed by: kinase, isomerase, dehydrogenase, decarboxylase,

carboxylase Glycolysis: steps & net reaction Pyruvate conversion to acetyl Coenzyme A Gluconeogenesis: steps in synthesis of glucose Catabolism of Triacylglycerols: beta-oxidation Synthesis of ketone bodies: ketogenesis Catabolism of Amino acids:

transamination & oxidative deamination 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

Metabolism

Step 2 of Metabolism

Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.

• Fatty acid oxidation

• Glycolysis

• Amino Acid Catabolism

All lead to the production of Acetyl CoA

•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 (NH2) are converted to urea [(NH2)2C=O], which is excreted in urine.

Metabolism Step 2 of Metabolism: Urea Cycle

http://www.t3portal.org/T3_Portal_v1/!SSL!/WebHelp/ales_vancura Catabolism_of_amino_acids.htm

Biochemical Rxns

Common Enzymes

Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed. 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.

Glycolysis Definition

10Smith, Janice Gorzynski. General, Organic, & Biological Chemistry 2nd Ed.

•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.

•Steps [6] – [10] comprise the energy-generating phase, producing 1 NADH and 2 ATPs for each pyruvate formed.

•The 6-carbon glucose molecule is converted into two 3-carbon segments.

Glycolysis Energy Investment

Glycolysis Energy Generation

Glycolysis Step 1

•Step [1] begins with the phosphorylation of glucose into glucose 6-phosphate, using an ATP and a kinase enzyme.

Glycolysis Step 2

•Step [2] isomerizes glucose 6-phosphate to fructose 6-phosphate with an isomerase enzyme.

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.

Glycolysis Step 4

•Step [4] cleaves the fructose ring into a dihydroxyacetone phosphate and a glyceraldehyde 3-phosphate.

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.

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-bisphospho- glycerate and NADH.

Glycolysis Step 7

•In step [7], the phosphate group is transferred onto an ADP with a kinase enzyme, forming 3-phosphoglycerate and ATP.

Glycolysis Step 8

•In step [8], the phosphate group is isomerized to a new position in 2-phosphoglycerate.

Glycolysis Step 9

•In step [9], water is lost to form phosphoenol- pyruvate.

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.

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.

Pyruvate can be converted into three possibleproducts depending on the conditions and the organism.

under aerobicconditions

under anaerobicconditions

in fermentationby microorganisms

Glycolysis Pyruvate

Glycolysis ATP Yield

2 x 2.5 ATP = 5 ATP

2 ATP 6 x 2.5 = 15 ATP

2 x 1.5 = 3 ATP

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.

Gluconeogenesis Cori Cycle

CHAPTER 24: Carbohydrate, Lipid, & Protein Metabolism General, Organic, & Biological Chemistry...

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