K Citric acid cycle 2 - Citric Acid Cycle Part II Citric...

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itric Acid Cycle Part II Citric Acid Cycle. Part II earning Objectives • Eight reactions and eight enzymes of the citric acid cycle Learning Objectives egulation of the citric acid cycle •ATP energy equivalent released in glucose catabolism • Regulation of the citric acid cycle • Metabolic reactions related to the citric acid cycle
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1. Citrate Synthase • Catalyzes the condensation of Acetyl- A d l tt CoA and oxaloacetate • The initial reaction of the citric acid cle cycle • Carbon atoms from carbohydrates, fatty acids, and amino acids enter the cycle in OO - COO - H O the form of acetyl group attached to CoA. COO C=O CH 2 HO-C-COO - CH 2 CH + CH 3 -C(O)-S-CoA 2 S oA COO - COO - Oxaloacetate Citrate Acetyl-CoA HS-CoA Δ G 0' -32 kJ/mol
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2. Aconitase • Aconitase catalyzes the reversible omerization of citrate and isocitrate isomerization of citrate and isocitrate, with cis -aconitate as an intermediate. he hydration of the double bond of • The hydration of the double bond of cis-aconitate could yield four stereoisomers. The enzyme catalyzes COO - H H O COO - H COO - H H O synthesis of only one isomer, isocitrate. HO-C-COO - CH 2 CH 2 2 C-COO - CH 2 CH H-C-COO - CH 2 HO-C-H 2 COO - Citrate COO - COO - cis -Aconitate Isocitrate
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3. NAD + -Dependent ocitrate Dehydrogenase • The enzyme catalyzes the oxidative ecarboxylation of isocitrate to Isocitrate Dehydrogenase decarboxylation of isocitrate to α - ketoglutarate. The reaction produces CO 2 and NADH. •The CO 2 carbon entered the first stage of the citric acid cycle as a mponent of oxaloacetate rather than COO - COO - COO - NADH COO - component of oxaloacetate rather than a component of Acetyl-CoA.
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This note was uploaded on 04/10/2011 for the course SCIENCE 2EE3 taught by Professor Zhorov during the Spring '11 term at McMaster University.

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K Citric acid cycle 2 - Citric Acid Cycle Part II Citric...

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