vit E Flashcards

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1
Q

Generation of free radicals in oxidative stress is associated with damage to what cellular structures

A

lipid peroxidation

protein oxidation

DNA and RNA oxidation - (Attacking DNA prevents cell from surviving)

mitochondrial abnormalities

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2
Q

what type of vitamin is vit C

A

lipid soluble

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3
Q

vit C protects lipids from what

A

free radicals and oxidative stress

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4
Q

explain lipid peroxidation

A

Free radical removes hydrogen from an unsaturated carbon atom on lipid (e.g. membrane phospholipids) to form lipid radical

LH		+	X*		L*	+	XH

The lipid radical reacts with molecular oxygen to form a peroxyl radical, LOO*

Lipids with double bond are vulnerable to attack these are found in membranes

The peroxyl radical can react with other membrane lipids to form a lipid hydroperoxide and another lipid radical

LOO*	+	LH		LOOH	+	L*

i.e. self-perpetuating cycle

Lipid hydroperoxides can form toxic, unsaturated aldehydes (not free radicals but continuously made by this cycle and can eventually cause damage to tissue) e.g. 4-hydroxy-nonenal

Oxidative stress has resulted in this cycle and so higher levels of these unsat aldehydes which toxic to neurons, neurons die and cause damage such as aszhymers

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5
Q

explain vitamin E, alpha tocopherol

A

Can reduce lipid peroxidation

LOO*	+	TOH		LOOH	+	TO*
  • TOH = tocopherol – this is more stable and not a lipid radicals so breaks cycle
  • LOO = lipid peroxide radicals

Tocopherol radical more stable and does not regenerate lipid peroxides i.e. cycle is broken

Vitamin C can recycle tocopherol radical to form regenerated tocopherol, so it can be used to break more cycles by moping up these free radicals

AH2	+	TO*		AH-	+	TOH
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6
Q

explain the regeneration of ascorbate

A

Can be regenerated by several mechanisms, including niacin and glutathione

 2AH-   +   NADH	 	2AH2   +   NAD+

2AH-   +   2GSH	 	2AH2   +   GSSG

First reaction is reduction of ascorbate to its reduced form
Second reaction is similar but uses glutathione

These are used to regenerate ascorbate

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7
Q

explain the vitamin E structures

A

alpha-tocopherol has methyl groups at R1, R2 and R3- highest activity
beta R1 + R3, gamma R2 + R3, delta R3

Tocopherol - It’s a saturated straight chain . This one has higher activity. The alpha version of this has greatest activity

Tocotrienols are unsaturated so have double bond on straight chain

Beta tocopherol has methyl groups at different R groups

Most biologically active form is alpha form

tocopherols and tocotrienols are mirror images but the trineols have a double bond

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8
Q

sources of vit E

A

plant oils
milk
wholemeal flour
wheat germ
wholemeal bread
meats
seeds and nuts
fruit and veg

Vit e is lipid soluble so its expected to be associated with oils, particularly plant oils

Animal products have less high a source

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9
Q

what are the vit e requirements determined by

A

by PUFA intake
(6 % energy intake)

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10
Q

what are the vit e RNIs for men and women

A

0.4 mg a-tocopherol eq./g PUFA intake, so RNI:

7 mg/d in males
5 mg/d in females

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11
Q

what is the uk intake range of vit c

A

2-27 (average of 10) mg/d

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12
Q

diets low in what cause vit e requirements to be greater

A

low-selenium (antioxidant nutrient) diets

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13
Q

higher vit e consumption is required for diets high in what

A

poly unsat fatty acid intake

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