NUTR 3210 Study Guide - Final Guide: Glutathione Peroxidase, Hydrogen Peroxide, Glutathione
28 Apr 2018
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Department
Course
Professor
Micronutrients 2
• What are Redox reactions?
- Involve the transfer of e- between 2 substrates
- The primary e- carriers in the body are NADH and FADH2
- Important b/c helps with creation of ATP
• What are reactive oxygen species (ROS)?
- Radicals have unpaire e- = unbalanced e-, they steal e- = causes imbalance =
problem
- ROS produced as a byproduct of the ETC, when proper e- flow fails
- They happen in an O2-rich enviroment, where O2 reacts with e-
- Generally: O2 ----------> 2H2O (ideally, O2 reacts with 4 e-)
-BUT mitochondrial leakage happens:
- O2 -----------> O2.- superoxide anion radical (O2 reacts with 1 e-)
- O2.- ----------> H2O2 (O2.- reacts with another e-) (SOD released)
- H2O2 ---------> OH. Hydroxy radical (most reactive, can attach DNA,lipids,etc
- H2O2 + glutathione peroxidase → 2H2O
• What’s up with vitamin E?
- Encompasses 8 compounds (vitamers)
→ 4 Tocopherols
- saturated side chains with 16 carbons
→ 4 Tocotrienols
- unsaturated side chains with 16 carbons
- Only a-tocopherol has significant activity in the body = most biologically active
- no inter-conversion of vitamers in animals – distinct molecules
- All are found naturally in food
- Rats can’t reproduce when vit.E absent from diet
• What are Tocopherols?
- All have ring structure, position of methyl group is what distinguishes them
- alpha is the most methylated ring = can fit well in a transport protein
- HYDROXYL GROUP = ANTIOXIDANT SITE
- Found ‘free’ in foods:
→ found in almonds, plant oils, etc
→ directly absorbed, passively
- Natural a-tocopherol is RRR: fits in tocopherol transfer protein TTP (perfect fit)
• What are tocotrienols?
- All ring structure, found esterified in foods, requires pancreatic esterase
digestion before absorption
- Lower levels in food compared to tocopherols
- They have antioxidant activity in the LIVER ONLY
• How does Vitamin E intake work?
- Food sources: nuts, seeds, veg.oils, leafy greens
→ sensitive to food preparation + storage (roasting nuts decreases vit.E)
→ Mostly obtained from plants b/c stored in fat in animals (we don’t eat fat)
- RDA established using only a-tocopherol
→ estimated based on crude tests examining RBC hemolysis (releases
hemoglobin) in presence od dilute H2O2 → >20% RBC hemolysis = vit.E deficiency
- RDA high for pregnant women → antioxidant compensates for increase ROS
- UL = 1000mg/day = internal bleeding
- Deficiency = rare but can happen in: premature infants (increase O2=ROS),
people w/ malabsorption disorders, genetic defects in lipoproteins/TTP
Document Summary
Involve the transfer of e- between 2 substrates. The primary e- carriers in the body are nadh and fadh2. Radicals have unpaire e- = unbalanced e-, they steal e- = causes imbalance = problem. Ros produced as a byproduct of the etc, when proper e- flow fails. They happen in an o2-rich enviroment, where o2 reacts with e- Generally: o2 ----------> 2h2o (ideally, o2 reacts with 4 e-) O2 -----------> o2. - superoxide anion radical (o2 reacts with 1 e-) O2. - ----------> h2o2 (o2. - reacts with another e-) (sod released) Only a-tocopherol has significant activity in the body = most biologically active. No inter-conversion of vitamers in animals distinct molecules. All have ring structure, position of methyl group is what distinguishes them. Alpha is the most methylated ring = can fit well in a transport protein. All ring structure, found esterified in foods, requires pancreatic esterase digestion before absorption. Lower levels in food compared to tocopherols.
