lecture12_10_14_08b

lecture12_10_14_08b - Lecture 12 Vitamins and Coenzymes...

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1 Vitamins and Coenzymes Overview: • vitamins: essential nutrients required in small amounts • coenzymes: most are modified forms of vitamins • water-soluble vitamins & coenzymes TPP, pyridoxal phosphate, flavins, coenzyme A, biotin, folate, Vit B12, Fe-containing coenzymes • metal cofactors • lipid-soluble vitamins Lecture 12 HW: see handout; 15.1, 15.7, 15.8, 15.9 Roles of vitamins and coenzymes • Metabolic reactions involve chemical changes that could not be brought about by the structures of amino acid side-chain functional groups acting by themselves. In catalyzing reactions, enzymes act in cooperation with smaller organic molecules or metal cations that possess special chemical reactivities or structural properties that are useful for catalyzing reactions. • Vitamins: organic molecules; essential nutrients required in small amounts. • Coenzymes: non-protein molecules that function as essential parts of enzymes. They also serve as carriers that accept or donate chemical groups, H atoms, or electrons.
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2 Roles of vitamins and coenzymes • Vitamins: first was thiamine (discovered in 1911) • two classes: water soluble or lipid soluble • most coenzymes are modified forms of vitamins; modifications take place in the organism after ingestion of vitamins Water soluble: Thiamine (B 1 ); Riboflavin (B 2 ); Pyridoxine (B 6 ); Nicotinic Acid (Niacin); Panthothenic Acid; Biotin; Folic Acid; Vitamin B 12 ; Vitamin C Lipid soluble: Vitamin A; Vitamin D; Vitamin E; Vitamin K (not coenzymes) Others: Inositol; Choline; Carnitine; α -Lipoic Acid; p-Aminobenzoate (PABA); Coenzyme Q Roles of vitamins and coenzymes Three groups 1) High group transfer potential (e.g., ATP, GTP); function in energy coupling within cells 2) Alter structure of a substrate to permit it to react more readily (e.g., coenzyme A, pyridoxal phosphate, thiamin diphosphate, Vit B 12 ) 3) Oxidative coenzymes with specific oxidation-reduction potentials (NAD + , NADP + , FAD, lipoic acid); carriers of hydrogen atoms or electrons
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3 Vitamin deficiency can lead to disease
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4 syntheses of vitamins are complex (many steps) humans require vitamins in the diet Coenzyme A FAD, FMN Pyridoxal 5’ phosphate Nicotinamide NADH, NADPH lipid soluble
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5 Thiamine pyrophosphate (TPP) SN CH 3 N N CH 3 NH 2 + H O P OO O P O Thiamine pyrophosphate C O C O C O C OH OH H H Thiamine, or vitamin B 1 , is converted to TPP , the essential coenzyme involved in the actions of enzymes that
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This note was uploaded on 08/04/2010 for the course CHM 6620 taught by Professor Dr.christinechow during the Fall '08 term at Wayne State University.

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lecture12_10_14_08b - Lecture 12 Vitamins and Coenzymes...

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