Nutrients, Oxidation and Antioxidants Flashcards Preview

CMBM exam 3 > Nutrients, Oxidation and Antioxidants > Flashcards

Flashcards in Nutrients, Oxidation and Antioxidants Deck (85):
1

Is vitamin E water or lipid soluble?

Lipid soluble

2

Is vitamin C water or lipid soluble?

Water soluble

3

What is oxidative stress?

O2 will steal an electron from a reduced metal, flavin etc and become superoxide) O2-

4

Superoxide and its products are known as;

Reactive Oxygen Species or ROS

5

The gas hormone nitric oxide (NO) is known as a;

Reactive Nitrogen Species (RNS)

6

How are ROS and RNS formed?

By accident in the electron transport chain
On purpose by immune cells

7

What can have its structure modified by oxidative or nitrosative stress?

Proteins, lipids, carbohydrates, individual nucleotide bases

8

Is it good or bad that a hydroxyl group can react with anything around it?

Bad

9

What can aldehydes do that are considered bad?

Create cross links between proteins

10

How is iron important?

Key role in many enzymes (cytochromes)
Catalysis and electron transfer, oxygen transport

11

How is iron toxic?

It is insoluble in presence of oxygen
Catalyzes the Haber-Weiss-Fenton Reactions
Produces a free radical hydroxyl

12

How does iron help defend against the toxins it makes?

With Superoxide dismutase to aid in conversion of superoxide to more stable form

13

Where and how is iron stored?

In ferritin and hemosiderin mostly in the liver

14

What molecule moves iron from various organs and cells into tissues and bones?

Transferrin

15

How much iron should a person have in a day to maintain stores?

At least 8 mg

16

How is the transferrin receptor complex internalized?

By receptor medicated endocytosis

17

How is iron release?

By acidification

18

How is non-heme iron uptake inhibited?

By phytate and polyphenols in common food (plant sources) like;
- black tea
- cocoa
- chamomile
Polyphenols numerous rings chelate the iron increasing its elimination

19

How is iron uptake stimulated?

Vitamin C
Organic acids
Heme

20

What is a hereditary excess in iron called?

Hemochromatosis

21

What is a dietary overload of iron called and how can someone get it?

Hemosiderosis
Alcohol (red wines) and over using supplements (children)

22

What drugs does iron decrease the absorption of?

Thyroxine, tetracyclin, ciprofaloxacin
occurs because numerous rings on the molecules act as chelators and this more effectively eliminates the drug and iron along with it

23

What is anemia?

Abnormally low blood hemoglobin

24

What enzymes can protect you from reactive oxygen species?

Superoxidase dismutases
Catalases
Peroxidases

25

What chemicals can protect you from ROS?

Bilirubin, glutathione, catalase, vitamin E, B-carotene and ascorbate (vit C)

26

What is glutathione?

A small tripeptide reversibly oxidized/reduced and can be regenerated by NADPH and glutathione reductase

27

Superoxide Dismutase

catalyzes superoxide to hydrogen peroxide

28

What is the danger in an ischemic/reperfusion injury?

the initial return of oxygen creates a burst of ROS species

29

Reactive Nitrogen species -RNS

NO
Peroxynitrite is ONOO- which is O2- + NO

30

Although H2O2 is not a free radical but ...

it can generate free radicals by encountering a transition metal

31

Lipid degradation generates

Peroxyl radicals

32

HOCl

produced by neutrophils during respiratory burst

33

Peroxynitrite

RNOS
strong oxidizing agent that is not a free radical
can generate NO2 which is a radical

34

what AA is important because it can be reversibly oxidized and reduced?

Methionine
this requires a reduced thiol such as glutathione

35

why are aldehydes so detrimental?

they crosslink proteins preventing them from functioning and making the breakdown and elimination difficult

36

What is Vit E's role in lipid oxidation ?

it prevents propagation of damage by acting as a sponge

37

Influx of intracellular calcium causes?

cellular death through activation of numerous intracellular pathways

38

what complicates the monitoring of oxidative damage in the vascular system?

oxidative damage not necessarily reflected by biomarkers and cannot be used as therapeutic targets
damage build ups in the subendothelial space

39

Haber Weiss Fenton reaction

(1) Fe+2 + O2 -> Fe+3 + O2*-
(2) 2 O2*- + 2H+ --> H2O2 + O2
(3) Fe+2 + H2O2 --> OH* + OH- + Fe+3

40

What transition metal in non reactive in biosystems?

Zinc

41

In regards to reduction potential, the more negative it is ....

the more likely it will GIVE UP electrons

42

What aids Iron absorption?

Vit C by acting as an electron donor converting Fe+3 to Fe+2 which is more soluble

43

In general, what effects metal solubility?

very insoluble at pH 7
but most are very soluble in acid

44

Freidreich ataxia

hereditary ataxia
defective frataxin - Fe cant be exported from Mitochondria and iron builds up in the nervous system

45

What metal is required for Iron absorption?

Cu

46

What can Fe deficiency lead to ?

lead poisoning because DMT/Divalent metal transporter expression is increased and it nonspecifically uptakes other metals as well

47

What molecules act as buffers to maintain electrical potentials in cells?

NAD(P), glutathione and Ascorbate
all these uptake electrons at different ranges to cover a wide range of redox potentials to maintain the electrical balance in cells
similar to how pH is maintained in the blood

48

How was it determined that Vitamin E was a requirement in the human body?

Patients with fat malabsoprtion syndromes were shown to have low levels of vitamin E

49

What sequesters Fe and Cu ions which prevents ROS?

Ceroplasmin (Cu), albumin (metals) and transferrin

50

What is Vitamin E actually?

A collection of molecules which function like alpha-tocopherol (alpha, beta, gamma, delta)

51

What is the main function of vit E?

Antioxidant
Stops propagation of free-radical damage in membranes
May prevent fatty acid damage in membranes

52

Tocopheryl esters (a form of vit E) are broken up by;

Pancreatic esterases (which also break up fatty acids)

53

What is essential for vit E absorption?

Bile acids
Deficiency occurs in fat malabsorption
which makes sense since Vit E is fat soluble

54

True or False
Like other fat soluble vitamins, E accumulates in toxic levels.

False

55

What uptakes vit E?

Chylomicrons

56

How is vit E oxidized and excreted?

Omega-oxidation by cytochrome P450
Removed in urine or bile

57

What large organ is also important for vit E excretion?

Skin - sebaceous glands

58

If there is a deficiency in vit E what are some diagnosis that can develop?

Retintis pigmentosa, neurological symptoms

59

There is only one type of organism that can make vit E, what is it?

Plants
Best sources are veggie oils

60

If you are deficient in alpha-tocopherol symptoms of ____ are mimicked.

Freidreich's ataxia

61

What can regenerate reduced vit E?

Vitamin C

62

What is vit C's main function?

Collegen biosynthesis
converts Proline to hydroxyproline
converts Lysine to hydroxylysine for crosslinking

63

L-ascorbic acid is derived from ____.

D-glucuronate
structure similar to glucose, can be uptaken by GLUT4

64

How many electrons can vit C donate? What does it use to regenerate?

2
NAD(P)H or glutathione

65

What is a deficiency in vit C called?

Scurvy

66

What are some symptoms of scurvy?

Connective tissue weakness, vascular damage, hemorrhagia, bleeding gums, poor wound and bone healing

67

What happens if there is excess vit C?

Hypoglycemia (blocks glucose uptake), kidney stones, indigestion, dissolves tooth enamel
No direct evidence that megadose helps colds or flu

68

What organ needs the most vit C?

pituitary gland
maybe cause its highly sensitive oxidative damage?

69

Do vitamins C and E aid in primary prevention of total cancer incidence or mortality?

No

70

In women with cardiovascular event who have high risk CVD, does ascorbic acid, vit E or beta carotene protect against it?

No

71

Do vit C and E help prevent prostate cancer?

No

72

Does vitamin C decrease the risk of diabetes?

Yes

73

Does multivitamin supplementation prevent cancer or CVD?

Perhaps, very limited evidence

74

what chemicals absorb electrons?

bilirubin, glutathione, ascorbate (vit c)

75

Glutathione is a small tripeptide composed of ...

glutamate, cysteine and glycine

76

what contributes to Glutathione's reversibly oxidation/reduction ability?

it is a sulfhydryl, the sulfur atoms can easily lose electrons or be partially ionized
it can also be nitrosylated

77

What state is the glutathione pool maintained in ?

Reduced state (SH)

(S-S) is the oxidized state (from 4 to 2 electrons)

78

What are the defenses in the blood/plasma against reactive oxygen species?

Vitamin C
Bilirubin
uric acid

79

why can't an anemic (low heme) pt be given IV heme?

Free Heme in the body is actually toxic
Its is normally bound to Haptoglobin or Hemopexin in the blood. The molecules clean up heme from lysed RBCs

80

LDLs contain a significant amount of ?

Vitamin E which helps to protect them oxidation

81

what improves bioavailability of Vit E?

the fat content of food
2 times more available when taken with milk vs. OJ

82

Can vitamin E be stored?

yes in Adipose tissue

83

What else is Vit C involved in?

synthesis of adrenal hormones
drug metabolism
folate metabolism
stimulates iron uptake

84

what patients should consider taking nutrient supplements?

older adults
pregnant women
pt who are food insecure
alcohol dependent
strict vegetarians and vegans (for these ppl when genetics may affect nutrition)
those on drug regimens that alter metabolism/excretion

85

A common measure of oxidative stress in plasma?

Malondialdehyde