BIOL 380 Lecture Notes - Lecture 8: Nyctalopia, Retina, Metastasis
19 Jun 2018
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Victoria Richard BIOL 380 Lecture 8: nutrients involved in antioxidant function
Antioxidants are compounds that protect cells from the damage caused by oxidation.
Oxidation and reduction: exchange reactions
- Oxidation is a chemical reaction in which atoms lose electrons
- Reduction occurs when atoms gain a electron
Free radicals
- Stable atoms have an even number of electrons (pairs) orbiting
- Electron loss during oxidation leaves an off number or unpaired electron
- Unstable atoms are called free radicals
-Reactive oxygen species (ROS): oxygen molecule that
becomes a free radical (superoxide anion)
- Free radicals like to scavenge electrons from other
molecules, turning them into free radicals
- Free radicals contain an unpaired electron that strongly reacts with electrons in proteins, DNA,
LDL and phospholipids, disrupting bonds in the molecules (perpetuating the cycle of free
radicals)
- Free radicals are like robbers which are deficient in energy
- Free radicals attack and snatch energy from the other cells to satisfy themselves
- Unpaired electron exerts a powerful attraction toward all stble molecules around it
What causes free radicals?
- Metabolic processes (rxns are never perfect)
- Immune system fighting infections
- Environmental factors
oPollution
oExcess sunlight
oToxic substances
oRadiation
oTobacco smoke
Free radicals damage cell membranes
- Free radicals form within the phospholipid bilayers of cell membranes and steal electrons
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oDamaged lipid molecules can cause cell membrane to lose it’s integrity
What are antioxidants?
- Oxidants (free radicals) are chemicals that have high affinity for
electrons
oSome of the strongest oxidants are free radicals that are
The by-product of normal cellular metabolism
Produced during stress
Produced after an exposure to UV, radiation, smoke, pollution and toxins
- Anti-oxidants prevent the potential harmful effects of oxidants
*** know for quiz
1. Antioxidant vitamins donate their electrons or hydrogen to free radicals to stabilize them and
reduce oxidation damage
2. Antioxidant minerals act as cofactors within enzyme systems that convert free radicals to less
damaging substances that can be excreted (selenium, copper, iron, zinc, …)
3. Other compounds such as beta-carotene and phytochemicals stabilize free radicals
oPlant based sources
oNot necessary in our diet
oNo minimum requirement intake amount for B-carotene but its intake can be beneficial
Antioxidant enzymes
-Superoxide dismutase converts free radicals to less damaging substances, such
as hydrogen peroxide (H2O2)
-Catalase and glutathione peroxidase remove H2O2
Antioxidant nutrients
- Nutrients with antioxidant properties
oVitamin E
oVitamin C
oBeta carotene (precursor of vitamin A)
oVitamin A
oSelenium
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Vitamin E
- Fat soluble
- Absorbed with dietary fats
- Enters body within chylomicron transported within VLDL and LDL enters cell
membranes when lipoproteins are disassembled by LL or on LDL receptors
- Stored in adipose tissue and cell membranes (so toxicity can be a thing)
Forms of vitamin E
- Tocopherol compounds are the biologically active forms
- Alpha-tocopherol is most active (potent), found in food and supplements
- Food labels and supplements: expressed as alpha-tocopherol equivalents or
international units (IU). Ex:
oIn foods 1 alpha-tocopherol Eq. = 1 mg vit E
oIn natural supplements 1 IU = 0.67 mg alpha tocopherol Eq
In supplements they are more bioavailable
Functions of vitamin E
- Antioxidant: donates an electron to free radicals, stabilizing them and preventing them from
destabilizing other molecules. Once vitamin E is oxidized, it is either excreted from the body or
recycled back into active vitamin E (with the help of vitamin C)
- Protects polyunsaturated fatty acids (PUFAs), fatty cell components and LDLs from oxidization
(associated with lower heart disease risk)
- Added to oil-based foods and skincare products to reduce rancidity and spoilage
- Normal nerve and muscle development
- Enhances immune system
- Promotes vitamin A absorption, if low
- Protects membranes of red blood cells from oxidation and plays a critical role in protecting the
cells of our lungs, which are constantly exposed to bad sh!t in the air
RDA for vitamin E
- RDA: 15 mg alpha-tocopherol per day
- Sufficient to prevent erythrocyte hemolysis, rupturing (lysis) of red blood cells (erythrocytes)
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Document Summary
Victoria richard biol 380 lecture 8: nutrients involved in antioxidant function. Antioxidants are compounds that protect cells from the damage caused by oxidation. Oxidation is a chemical reaction in which atoms lose electrons. Stable atoms have an even number of electrons (pairs) orbiting. Electron loss during oxidation leaves an off number or unpaired electron. Reactive oxygen species (ros): oxygen molecule that becomes a free radical (superoxide anion) Free radicals like to scavenge electrons from other molecules, turning them into free radicals. Free radicals contain an unpaired electron that strongly reacts with electrons in proteins, dna, Ldl and phospholipids, disrupting bonds in the molecules (perpetuating the cycle of free radicals) Free radicals are like robbers which are deficient in energy. Free radicals attack and snatch energy from the other cells to satisfy themselves. Unpaired electron exerts a powerful attraction toward all stble molecules around it. Environmental factors: pollution, excess sunlight, toxic substances, radiation, tobacco smoke.
