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Flashcards in Nutrition and Antioxidants Deck (57)
1

Is vitamin E (lipid/water) soluble?

lipid

2

Is Vitamin C (lipid/water) soluble?

water

3

Define Reactive Oxygen Species (ROS)

superoxide and its subsequent products

-O2 will often steal an electron from reduced metals, flavins, quinols, etc become "superoxide" or O2-

-very reactive
-will combine with anything

4

Give example of a Reactive Nitrogen Species.

gas hormone nitric oxide (NO)

5

Give some examples of Reactive Oxygen Species.

Superoxide (O2-)
Hydrogen Peroxide (H2O2)
Hydroxyl radical (OH-)

6

Oxidative and Nitrosative damage are commonly linked with disease either as a cause or side-effect.

FYI

7

What are four ways that oxidative and nitrosative stress can damage biological molecules?

1. Modification of structure and function of CARBOHYDRATES
2. Modification of structure and function of PROTEINS
3. Modification of LIPID (peroxidation)
4. Modification of individual NUCLEOTIDE BASES

8

How do ROS damage lipids?

ROS can led to chain reaction due to oxygen reacting with lipid.

9

Why are aldehydes so reactive?

create crosslinks between proteins

ex) formaldehyde

10

Patient is suffering from ischemia/reperfusion injury. Damage is primarily caused by:

initial return of oxygen to normal levels

11

LDLs are protected from oxidative modification in systemic circulation due to presence of circulating anti-oxidants. What happens when LDLs are trapped in the sub-endothelial space?

ROS reacts with LDL and leads to oxidized LDL (oxLDL).

oxLDL
- is a chemoattractant to circulating monocytes
- contributes to endothelial dysfunction
-further ROS formation

12

How does cytochrome C function in mitochondrial injury?

acts as an apoptic signal

13

Iron can play the following roles:

role in many enzymes
-catalysis
-electron transfer
-oxygen transport

14

What reaction can iron catalyze?

Haber-Weiss-Fenton reactions

15

Describe the reactions that iron can undergo.

oxidation
reduction

Leo (lose electron Oxidized)
Ger (gain electron Reduced)

16

How is iron stored in the body?

ferritin
hemosiderin
(mostly in liver)

17

How much iron is required per day to maintain stores with a mixed diet?

8 mg per day

18

How is iron taken up by the body?

transferrin - specific cell membrane receptors on target cells

Tf-receptor complex is internalized by receptor-mediated endocytosis

Fe is released by acidification

19

How is non-heme taken up by the body?

Stimulated:
Vit C
organic acids
Heme

Inhibited:
black tea
cocoa
chamomile

20

What happens in the presence of iron excess?

hemochromatosis (hereditary defect)

hemosiderosis (dietary overload)
-alcohol in excess
-children ingesting Fe supplements

Oxidative stress

Decrese absorption of thyrozine, tetracycline, ciprofaloxacin

possible heart disease

21

What can lead to iron deficiency?

diet deficiencies
infection (H. pylori)
inflammation
other vitamin deficiencies (Vit C)

Result: anemias
- can exacerbated other problems (lead poisoning)

22

What are some defense mechanisms that protect against oxidative stress?

Chemical:
Vitamin C
Vitamin E
B-carotene
Glutathione
Bilirubin

Enzymatic:
Super Oxide Dismutase (SOD)
catalase
peroxidases

23

Why does the cell have different redox active organic components?

Can donate or accept electrons at different electrical potentials

Overlap allows a wide range of reactions

24

Which enzymes protect you from ROS?

superoxide dismutase
catalase
peroxidases

25

Which chemicals protect you from ROS?

bilirubin
glutathione
Vitamin C
Vitamin E

26

Describe glutathione.

Small, modified tripeptide reversible oxidized/reduced
-thiol group

- good source of eletroncs to reduce ROS

- regenerated w/electron from NADPH by Glutathione reductase

27

What is the concentration of glutathione?

[millimolar]

28

What is the MAIN function of Vitamin E?

antioxidant - stops propagation of free-radical damage in membranes

29

Vitamin E will be deficient when there is ?

fat malabsorption

30

Bile acids are essential for which vitamin to be absorbed?

Vitamin E

31

Where is the bulk of Vitamin E stored?

adipose tissue

32

A deficiency in Vitamin E lease to?

retinitis pigmentosa
neurological symptoms

33

What is the RDA of Vitamin E?

15 mg/day

** does not accumulate in the liver to toxic levels

34

Scavenges oxygen and free radicals

Reducing reagent

35

A-tocopherol deficiency can lead to ?

ataxia

36

Bioavailability of Vitamin E depends on what 2 things?

bile acids
fat content of food
ex) 2x as available when taken with milk vs. orange guide

37

How is Vitamin E oxidized?

by w-oxidation by cytochrome P450

38

What is used to regenerate reduced Vitamin E?

Vitamin C

39

List three functions of Vitamin C

antioxidant
collagen biosynthesis
-proline
-lysine

Synthesis of:
-adrenal hormones
-drug metabolism
-folate metabolism
-stimulation iron uptake

40

How many electrons can Vitamin C donate?

2

41

How can Vitamin C be regenerated?

number of different enzymes using electrons from NAD(P)H or by glutathione

42

What is the first thing that is oxidized in plasma under oxidative stress?

Vitamin C

43

How does Vitamin C accumulate?

intracellularly via specific transporters AND by at least 4 glucose transporters (GLUT 1-4)

44

What is a result of Vitamin C deficiency?

Scurvy

45

How does Scurvy present?

connective tissue in muscle, skin, blood vessels

hemorrhagia
bleeding gums
weakness
poor wound healing or bone healing

46

What is the RDA for Vitamin C?

60 mg/day

47

What can excess (megadoses) of Vitamin C cause?

hypoglycemia
kidney stones
indigestion
dissolve teeth enamel (chewable forms)

48

$21 to 25 billion dollars is spent on supplements each year yet most are not supported by?

larger, randomized trials

49

Present evidence on the use of multivitamins (MVMs) is ?

insufficient

50

In the primary prevention of total cancer incidence or cancer mortality, Vitamin C, E or beta carotene offer?

no overall benefit

51

Regarding cardiovascular events among women with high risk for CVD, ascorbic acid, Vitamin E or beta carotene offer?

no overall effect

52

Evaluating the risk of prostate or total cancer, the use of Vitamin E or C offers?

no overall effect

53

The risk of major cardiovascular events in men, the use of Vitamin E or C offer?

no overall effect

54

Higher plasma Vitamin C levels and fruit and vegetable intake were associated with

decreased risk of diabetes

55

The groups most vulnerable to inadequacy of one or more nutrients are?

-older adults
-pregnant women
-people who are food insecure
- alcohol-dependent individuals
-strict vegetarians and vegans
-increased needs due to health conditions
-chronic use of medication that decreases nutrient absorption or changes metabolism

56

What benefit could pharmacologic doses of ascorbate provide?

prooxidant and decrease growth of aggressive tumor xenografts (in mice)

57

What was the effective concentration (sufficient to kill 50% of tumor cells) of ascorbate?

<10mM for 75% of tumor cells tested