Exam Four Learning Objectives

Exam Four Learning Objectives - Exam Four Learning...

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Exam Four Learning Objectives Chapter 14 – Lipid Metabolism 14.1. 1. Dietary triacylglycerols are the primary source of fatty acids used as metabolic fuel. 2. The reaction makes the formation of acyl-CoA spontaneous and irreversible. 14.2 1. Reactions of B oxidation a. Oxidation of acyl-CoA (first step) i. Reactants: Fatty acyl-CoA ii. Enzyme: Acyl-CoA dehydrogenase iii. Cofactors: FAD, Q iv. Products: Enoyl-CoA b. Second step i. Reactants: Enoyl-CoA ii. Enzyme: enoyl-CoA hydratase iii. Products: 3-Hydroxyacyl-CoA c. Third step i. Reactants: 3-Hydroxyacyl-CoA ii. Enzyme: 3-hydroxyacyl-CoA dehydrogenase iii. Cofactors: NAD+ iv. Products: Ketoacyl-CoA d. Fourth step i. Reactants: Ketoacyl-CoA ii. Enzyme: Thiolase iii. Products: Fatty acyl-CoA (2 carbons shorter) + Acetyl-CoA 2. ATP production
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a. One round of B oxidation produces 1 QH2, 1 NADH, and 1 Acetyl-CoA b. In the citric acid cycle, acetyl-CoA is converted to 3 NADH, 1 QH2, and 1 GTP. i. This leads to 12 ATP in oxidative phosphorylation. c. QH2 produces 2 ATP in oxidative phosphorylation. d. NADH produces 3 ATP in oxidative phosphorylation. e. This leads to a total production of 17 ATP. 14.3 1. Enzyme Activities a. Unsaturated Fatty Acids i. Reductase, isomerase ii. NADPH consumed iii. Rearrangement of cis/trans double bonds b. Odd-chain Fatty Acids i. Propionyl-CoA ii. Conversion of succinyl-CoA to pyruvate and then to acetyl-CoA 2. The peroxisome serves a chain-shortening system. 14.4 1. The pathways differ because of thermodynamic reasons. Fatty acid degradation is thermodynamically favorable, and fatty acid synthesis is naturally unfavorable. 2. Differences: a. Location: Degradation – Mitochondria / Synthesis – Cytosol b. Cofactors: Degradation – CoA / Synthesis – ACP i. Degradation – Ubiquinone and NAD+ / Synthesis – NADPH c. ATP Requirements: Degradation – 2 / Synthesis – 1 d. Intermediates:
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i. Degradation: Enoyl-CoA, 3-hydroxyacyl-CoA, Ketoacyl-CoA ii. Synthesis: Acetyoacyl-ACP, Hydroxybutyryl-ACP, Butenoyl-ACP, Butyryl-ACP, Palmitoyl-ACP 3. Functions: a. Elongases – Generates long-chain fatty acids b. Desaturases – Introduces double bonds into saturated fatty acids 14.5 Malonyl-CoA is a source of acetyl groups that are incorporated into fatty acids. 14.6 Ketone bodies are produced by the liver to supplement gluconeogenesis. o Acetoacetate o 3-hydroxybutyrate Both synthesized from acetyl-CoA in liver mitochondria by ketogenesis. Acetoacetate is produced when HMG-CoA is degraded by HMG-CoA lyase. 3-hydroxybutyrate is produced when acetoacetate is reduced. NADH is consumed. 14.7 1. CoA is converted to acyl-CoA by consuming ATP. 2. CTP is cleaved to form CDP-ethanolamine / CDP-choline. 3. Cyclooxygenase catalyzes the addition of two oxygen molecules.
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Exam Four Learning Objectives - Exam Four Learning...

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