Lecture 14- micronutrients - 2

Lecture 14- micronutrients - 2 - Micronutrients#2 Involved...

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Micronutrients #2: Involved in Oxidant Defense Vitamin E, Selenium, Vitamin C, Sulfur amino acids, Niacin, Riboflavin, Copper/Zinc/Manganese
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Reduction-Oxidation Reactions Reduction-oxidation reaction = Redox reaction Transfer of electrons between two substrates Biochemical reactions are essentially electron transfers Large number of our nutrients have redox functions Principle electron carriers NADH and FADH 2 Why is this important? Glycolysis Lactic Acid Production Pyruvate Dehydrogenation Kreb’s Cycle Gluconeogenesis β -oxidation
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Redox Reactions Oxidized losing electrons Reduced gaining electrons
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Reactive Oxygen Species (ROS) •ROS produced as a by-product of the ETC where electron flow fails (~1%) •Occurs in a O 2 -rich environment, so oxygen can bind electrons •Mutations in SOD = Lou Gehrig’s •H2O2 converted to H2O by catalase, glutathione peroxidase (selenium dependent), etc
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VITAMIN E
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Encompasses 8 compounds (vitamers) 4 tocopherols Have saturated side chains with 16 carbons 4 tocotrienols Have unsaturated side chains with 16 carbons Vitamers in both classes (α, β, γ, δ) Only α-tocopherol has biologic activity Can not interconvert vitamers All are found naturally in foods Tocopherol derived from Greek word: Tokos = “childbirth” & Phero = “to bear or bring forth” Based on work showing that rats couldn’t reproduce when vitamin E was absent from the diet Vitamin E
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Vitamin E – 4 Tocopherols Saturated side chain (phytyl tail) Nomenclature used to describe # and position of ring CH 3 groups α = most methylated The hydroxyl group (circled) is antioxidant site (necessary!) R and S configuration determined by first 3 CH 3 groups on side chain Natural α-tocopherol is RRR Fits in Tocopherol transfer protein (TTP)
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Vitamin E – 4 Tocotrienols Unsaturated side chain (phytyl tail) Rules for nomenclature the same Originally thought that tocotrienols don’t contribute towards Vit E requirement (absorbed, but not converted to α- tocopherol or recognized by TTP New evidence questions this…
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Vitamin E Intake Food sources: nuts, seeds, vegetable oils, leafy greens Susceptible to food preparation & storage (e.g. roasting nuts Vit E content) Mostly from plants because stored in fat in animals Dietary recommendations based on α-tocopherol only
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