antioxidants Flashcards
consumption of fruits and veggies decreases rates of:
_______
_____ _____
cancer
heart disease
list the micronutrient (essential) antioxidant defence system
Vit E Vit C Selenium, riboflavin, niacin zinc copper manganese iron beta carotene
why do we need antioxidants
balance between PROoxidants and ANTIoxidants
- oppose the toxic effects of oxygen
- 1-3% of oxygen results in Reactive oxygen species, which can be bad so we need to deal with these compounds
95% of oxygen is used for ________
energy production
oxidative process…oxidative phosphorylation
an increased ______ and decreased _______ results in a serious imbalance between ROS generation and antioxidant supply, termed _______ _____
RPS production
Antioxidant intake
Oxidative stress
cells can sometimes adapt to oxidative stress, but adapting to severe oxidative stress causes ____ ______
cell damage
when are free radicals formed
during oxidative metabolism
they contribute to oxidative stress
what is a free radical
molecules with one or more unpaired electron
_____ are very unstable and highly reactive
free radicals
in order for a free radical to be stable, what does it need to do? what can this cause?
steal an electron from another molecule
can set off a chain reaction
how do atoms bind together
by sharing electrons
what are the three types of free radicals
- ROS- Reactive oxygen species
- RNS: reactive nitrogen species
- R:other reactive species
free radicals are byproducts of ____________
normal cellular reactions
T/F?
free radicals have no useful biological funtion
false
they’re useful, just need to control their quantity
ROS
free radicals
unstable molecules
what are the two reasons for ROS generation
- useful production
2. accidental production
how can ROS be useful
- important defence mechanisms
- produced by activated phagocytes
- mechanism to kill bacteria and fungi
- mechanism to inactivate viruses
- sometimes inappropri
what are some reasons for accidental production of ROS
- instability in presence of oxygen
- many molecules spontaneously react with oxygen
- ETC: some electrons escape and react with oxygen, free radicals are formed
what is the best example of a free radical causing a chain reaction?
lipid peroxidation
what is needed in order for lipid peroxidation to happen
free radical
what are the two general steps of lipid peroxidation
1) initiation (generation of free radical)
2) propagation (free radical is regenerated in presence of oxygen)… reacts with an innocent FA, produces byproduct ROOH (fatty acid hydroxide) then the cycle continues
Fatty acid hydroperoxide (ROOH)
- can build up and cause oxidative stress
- can also combine with iron (bad when iron binds to COOH)
- produces hydroxy radical (worst case scenario)
- iron could also react with H2O2
hydroxy radical OH•
- is thought to initiate reaction of another radical
- very bad news
- no positive role in body at all
- reacts instantaneously with anything
- leads to all sorts of problems
Superoxide and hydrogen peroxide
-ROSs
superoxide= free radical (We have a way to deal with it)
hydrogen peroxied is an unstable form of oxygen (not a free radical)
- much less reactive than hydroxy radical
- can react with EACH OTHER to form hydroxy radical
- called the Harber-Weiss reaction…involved iron
what are some points about dealing with ROS
how do we deal with them
- need to keep them at manageable levels
- need to prevent oxidative damage
- need radical scavengers
how???? ANTIOXIDANTS
want antioxidants to react with free radicals before they react with something else
what is the goal of the micronutrient antioxidant defense system
avoid oxidative stress
what does the micronutrient antioxidant defence system allow for? and what is it formed from
allows balance between PROoxidant and ANTIoxidant systems
comes from vit and minerals in diet and enzymes (that need the vit and mineral)
in terms of antioxidative defence, what is Vit E involved in
Chain breaking:
able to terminate the chain reaction
key structural features :
1) OH groups (reacts with oxygen)
2) ring structure (makes it a non-reactive free radical, can delocalize the charge around its ring structure)
how does Vit E interact with lipid peroxidation cycle
takes away free radical by taking it upon itself–becoming a free radical itself..
stops chain reactions and acts as antioxidant and deals with the free radical
how is the Vit E radical formed after Vit E acts as an antioxidant dealt with
the key to dealing with the Vit E radical is Vit C
Vit C donates a hydrogen, and the Vit C can then be recycled back to Vit C without formation of a free radical
result: complete quenching of free radical
will not always have Vit E to deal with free radicals…but we do have _____ that can deal with ROOH
enzymes
what are important enzymes that deal with ROOH
Glutathione reductase and peroxidase
–>peroxidase processes the ROOH
superoxide dismutase
glutathione peroxidase and reductase convert _____ to ______
harmless compounds
both glutathione peroxidase and reductase need _____ to work
micronutrients
which nutrient does glutathione peroxidase need to work
selenium
which nutrients do glutathione reductase need to work
riboflavin
niacin
superoxide dismutase is an ______ enzyme that we have that can deal with ______ _____.
this produces _____ _____
endogenous
superoxide radicals
hydrogen peroxide….this then is metabolized by catalase (endogenous enzyme…needs IRON)
what does superoxide dismutase need in order to work
Zinc and Copper (cytoplasmic form)
Manganese (mitochondrial form)
iron is ironic
can be bad:
- reacts with ROOH to form hydroxyl radical via Harber-Weiss reaction
- also thought to contribute toward the initiation of Lipid peroxidation
can be good:
-needed for catalase enzyme to detoxify H2O2
Beta-Carotene
- precursor of Vit A
- unique antioxidant
- quenches single oxygen (not a Free radical itself but a potent generator of free radicals)
- can act as antioxidant but depends on partial pressure (relative to lungs, RBC membrane)
Beta carotene:
______-animal sources
______-plant sources
retinoid
carotenoids
what make beta-carotene a unique antixoidant
- depends on partial pressure of oxygen
- LOW pressure= acts as ANTIoxidant
- HIGH pressure= acts of PRO-oxidant
**Antioxidants and CVD
-oxidative damage to LDL greatly enhances development of atherosclerosis
(we dont want high oxidated LDL levels…this is worse than normal LDL)
- oxidized LDL accelerates several steps in the process of atherosclerosis
- Vit E inhibits oxidation of LDL
- Beat-carotene may decrease cell uptake of oxidized LDL
antioxidants and cancer
- consumption of fruits and veggies associated with dec risk of cancer
- intervention trails using supplemental antioxidants not as consistent
- often combined supplements given
- challanging to sort out interactions
two studies were conducted regarding the relationship betwen beta carotene supplementation and cancer, what was the result? was it good or bad?
bad.
studies showed in increase in lung cancer with beta carotene supplementation in male smokers
