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nutr 3330 midterm > antioxidants > Flashcards

antioxidants Flashcards

1
Q

consumption of fruits and veggies decreases rates of:
_______
_____ _____

A

cancer

heart disease

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2
Q

list the micronutrient (essential) antioxidant defence system

A 
Vit E
Vit C
Selenium, riboflavin, niacin
zinc copper manganese
iron
beta carotene
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3
Q

why do we need antioxidants

A

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
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4
Q

95% of oxygen is used for ________

A

energy production

oxidative process…oxidative phosphorylation

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5
Q

an increased ______ and decreased _______ results in a serious imbalance between ROS generation and antioxidant supply, termed _______ _____

A

RPS production

Antioxidant intake

Oxidative stress

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6
Q

cells can sometimes adapt to oxidative stress, but adapting to severe oxidative stress causes ____ ______

A

cell damage

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7
Q

when are free radicals formed

A

during oxidative metabolism

they contribute to oxidative stress

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8
Q

what is a free radical

A

molecules with one or more unpaired electron

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9
Q

_____ are very unstable and highly reactive

A

free radicals

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10
Q

in order for a free radical to be stable, what does it need to do? what can this cause?

A

steal an electron from another molecule

can set off a chain reaction

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11
Q

how do atoms bind together

A

by sharing electrons

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12
Q

what are the three types of free radicals

A
  • ROS- Reactive oxygen species
  • RNS: reactive nitrogen species
  • R:other reactive species
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13
Q

free radicals are byproducts of ____________

A

normal cellular reactions

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14
Q

T/F?

free radicals have no useful biological funtion

A

false

they’re useful, just need to control their quantity

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15
Q

ROS

A

free radicals

unstable molecules

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16
Q

what are the two reasons for ROS generation

A
  1. useful production

2. accidental production

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17
Q

how can ROS be useful

A
  • important defence mechanisms
  • produced by activated phagocytes
  • mechanism to kill bacteria and fungi
  • mechanism to inactivate viruses
  • sometimes inappropri
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18
Q

what are some reasons for accidental production of ROS

A
  • instability in presence of oxygen
  • many molecules spontaneously react with oxygen
  • ETC: some electrons escape and react with oxygen, free radicals are formed
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19
Q

what is the best example of a free radical causing a chain reaction?

A

lipid peroxidation

20
Q

what is needed in order for lipid peroxidation to happen

A

free radical

21
Q

what are the two general steps of lipid peroxidation

A

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

22
Q

Fatty acid hydroperoxide (ROOH)

A
  • 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
23
Q

hydroxy radical OH•

A
  • 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
24
Q

Superoxide and hydrogen peroxide

A

-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
25
Q

what are some points about dealing with ROS

how do we deal with them

A
  • 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

26
Q

what is the goal of the micronutrient antioxidant defense system

A

avoid oxidative stress

27
Q

what does the micronutrient antioxidant defence system allow for? and what is it formed from

A

allows balance between PROoxidant and ANTIoxidant systems

comes from vit and minerals in diet and enzymes (that need the vit and mineral)

28
Q

in terms of antioxidative defence, what is Vit E involved in

A

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)

29
Q

how does Vit E interact with lipid peroxidation cycle

A

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

30
Q

how is the Vit E radical formed after Vit E acts as an antioxidant dealt with

A

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

31
Q

will not always have Vit E to deal with free radicals…but we do have _____ that can deal with ROOH

A

enzymes

32
Q

what are important enzymes that deal with ROOH

A

Glutathione reductase and peroxidase
–>peroxidase processes the ROOH

superoxide dismutase

33
Q

glutathione peroxidase and reductase convert _____ to ______

A

harmless compounds

34
Q

both glutathione peroxidase and reductase need _____ to work

A

micronutrients

35
Q

which nutrient does glutathione peroxidase need to work

A

selenium

36
Q

which nutrients do glutathione reductase need to work

A

riboflavin

niacin

37
Q

superoxide dismutase is an ______ enzyme that we have that can deal with ______ _____.
this produces _____ _____

A

endogenous

superoxide radicals

hydrogen peroxide….this then is metabolized by catalase (endogenous enzyme…needs IRON)

38
Q

what does superoxide dismutase need in order to work

A

Zinc and Copper (cytoplasmic form)

Manganese (mitochondrial form)

39
Q

iron is ironic

A

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

40
Q

Beta-Carotene

A
  • 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)
41
Q

Beta carotene:

______-animal sources

______-plant sources

A

retinoid

carotenoids

42
Q

what make beta-carotene a unique antixoidant

A
  • depends on partial pressure of oxygen
  • LOW pressure= acts as ANTIoxidant
  • HIGH pressure= acts of PRO-oxidant
43
Q

**Antioxidants and CVD

A

-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
44
Q

antioxidants and cancer

A
  • 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
45
Q

two studies were conducted regarding the relationship betwen beta carotene supplementation and cancer, what was the result? was it good or bad?

A

bad.

studies showed in increase in lung cancer with beta carotene supplementation in male smokers

nutr 3330 midterm (13 decks)

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