Nutrition Chapter 10: Nutrients involved in Antioxidant Function and Vision

Oxidation (LEO)

loss of e-

Reduction (GER)

gain of e-

Free Radicals (FR)

• highly unstable atom with an unpaired electron

• commonly formed during metabolic processes, also inflammation, exposed to air pollution, UV rays, tobacco, smoke, asbestos

• destabilize other molecules (phospholipid in membrane

When destabilizing other molecules, antioxidants help with this….

in the phospholipid membrane-

disrupting hydrophobic tails → make hydrophilic→destabilization of membrane

destabilize proteins →

destabilize proteins → lose function

destabilize DNA →

destabilize DNA → mutations

Antioxidants include

1. vitamins A, C, E

2. Minerals: Se, Cu, Fe, Zn, Mn

3. phytochemicals

What do vitamins A,C,E do for antioxidants?

donate e- and hydrogen atoms to stabilize free radicals

What do minerals do for antioxidants?

• cofactors to antioxidant enzyme systems like H2O2

• Ex: superoxide dismutase- Cu, Mn, Zn

  • take FR & convert into something less damaging catalase (Fe) - H2O2 →remove from body

  • glutathione peroxidase (Se) - remove H2O2 (hydrogen peroxide)

What do phytochemicals do for antioxidants?

• typically found in plants

• Beta carotene - stabilize FR

Free Radicals damage cell proteins, DNA, and what else?

low-density lipoproteins (LDLs)

When having FRs, there is an increase risk for these chronic diseases

• cancer

• heart disease

• Type II diabetes

• Arthritis

• Cataracts

• Alzheimer’s

• Parkinson’s

Vitamin E

• fat soluble

• typically in chylomicrons → remnant → transported to liver → VLDL → released into blood → cells/tissues

• 90% stored in adipose tissue and cell membranes

• form alpha-tocopherol - donate e- (oxidized) & give e- to FR → then recycled or excreted

Vitamin E functions

• protect cell membrane → prevent oxidation of fatty acids

• protect LDLs form oxidation → reduce risk of CVD

• protect red blood cell membrane

• prevents blood clots → anticoagulant

• protect white blood cells → immune system function

• help absorb vitamin A

• inhibit protein kinase C → impact txn & tln of different genes → inhibit cell proliferation

Excess of Vitamin E causes what?

nausea, diarrhea, intestinal distress, increase anticoagulation, no clotting

Deficiency of Vitamin E causes what?

uncommon

stored in fatty tissues

can cause anemia

Vitamin C

• water soluble → can excrete

• most animals most vit. C thru glucose except humans and guinea pigs

Forms of Vitamin C

ascorbic acid

dehydroascorbic acid

Low [vitamin C]→ ______ → _______

Low [vitamin C]→active transport → absorbed by small intestine

High [vitamin C] → _________

High [vitamin C] → simple diffusion across membrane (DNA, bile, neurotransmitter synthesis)

Functions of Vitamin C

• coenzyme with collagen (procollagen → collagen)

  Contribute and stabilize FR

• antioxidant in extracellular fluids - in lungs

• lowering LDL-blood

• white blood cells

When vitamin E is oxidized, Vitamin C (ascorbic acid) does one of these two things

• e- donate e- → regenerate vitamin E

  OR

• dehydroascorbic acid → regenerate vit C (ascorbic acid)

Glutathione (GSH) → _______

remove e- and oxidize GSH → regenerate GSH by gaining e-

Excess of Vitamin C causes what

people with kidney disease taking supplements

Deficiency of Vitamin C causes what

• anemia

• in impoverished areas

• diarrhea

• failure to heal wounds

• alcohol and substance abuse

Vitamin A characteristics

• fat soluble

• stored in liver (90%)

  Three different forms

3 Forms of Vitamin A

• Retinol (alcohol)

• Retinal (aldehyde)

• Retinoic acid (acid)

Transport of Vitamin A starting with beta carotene

beta carotene → cut into 2 retinol molecules → small intestine → enterocytes → fatty acids attach → chylomicron → lymph → either cells for use or →liver for storage

Transport of Vitamin A starting with retinol

retinol + retinol binding proteins → H20 soluble → blood

Vitamin A with vision

retinal + opsin → rhodopsin → impacted by light in order to egnerate nerve impulse to brain for visualization to occur

Rhodopsin

• in rod cell membrane

• light sensitive pigment

Functions of Vitamin A

• vision

• cell differentiation

• reproduction

• bone growth

• sperm production and fertilization

• break down old bone and regenerate new bone in its place

What is the function of retinoic acid?

retinoic acid is a signaling molecule → gene expression → specialized cells (differentiation)

Excess of Vitamin A

• 3-4x RDA can be toxic (usually thru supplements)

• Symptoms: impact vision, loss of appetite, bone/joint pain, fatigue, hair loss

• in pregnant females-serious/severe birth defects, can result in abortion

Deficiency in Vitamin A

if bad enough → hardening of corneas → blindness

Characteristic of Selenium

• essential trace mineral

• absorbed by small instestine

• used in generating amino acid - selenocysteine

What is a selenoprotein?

protein with selenocysteine in it in which UGA codon codes for selenocysteine

Types of Selenoproteins

• glutathione peroxidase

• iodothyroine deiodinase

• SEPN1

Functions of glutathione peroxidase

• breaks down H2O2 → H2O

What can H2O2 (hydrogen peroxide) do?

since it can be a free radical → oxidative distress

you do not want this to ha

Functions of iodothyronine deiodinase

T4→T3 (active thyroid horma