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Flashcards in Micronutrients II - Vitamins Deck (93):
0

Vitamins

typically cofactors for enzymes
organic compounds required for diet in only small amounts to maintain fundamental cell functions
not catabolized
Organic

1

Which vitamins are most utilized in energy metabolism?

B vitamins

2

how many water soluble vitamins?

9

3

how many lipid soluble vitamins?

4

4

Vitamin-like compounds

Inositol
Choline
Lipoic Acid
PQQ-Pyrroloquinoline quinone

5

Inositol

phospholipids

6

Choline

in phospholipids, methyl donor
choline free diet could lead to liver damage

7

Lipoic Acid

not a vitamin but required for pyruvate decarboxylase
animals can make this

8

PQQ-pyrroloquinoline quinone

methoxatin
redox cofactor for quinoproteins
ex: flavoproteins - dehydrogenases

9

Vitamin D only needed when

sunlight is absent

10

Primary deficiency

lack of adequate intake in diet

11

causes of Primary deficiency

poor nutrition/food habits, poverty, ignorance of nutrition needs, insufficient food, lack of proper vitamin rich foods, food fads, food taboos, vitamin destruction, anorexia

12

Secondary deficiency

poor availability or utilization of a vitamin due to environmental or physiological conditions

13

Causes of secondary deficiency

poor digestions (achlorhydria-low gastric acid)
malabsorption (diarrhea, infections)
impaired utilization (drug therapy)

14

Vitamin deficiencies significant in

any pt with digestion/malabsorption problems
chronic substance abuse (alcohol) bad diet & inhibits uptake of vit
recent surgery, total parenteral nutrition
elderly, pregnant/breastfeeding, smokers, alcoholics, diabetics
risk thiamine deficiency with high CHO diet

15

What aids in fat soluble vitamin absorption?

Bile

16

digestive enzymes from pancreas help uptake

vitamin K

17

Bacteria in the gut make small amount of

vitamin K, B12, and biotin

18

Fat soluble vitamins are absorbed with

dietary fat

19

where are fat soluble vitamins stored?

liver and nonspecifically adipose tissue

20

Risk of toxicity with what vitamin?

B vitamins

21

Vitamin A

mixture of Retinoids
role in gene regulation - reproduction, embryogenesis, development, cell differentiation and proliferation) vision, maintenance of brain function and skin

22

Vitamin A deficiency

night blindness
hyperkeratosis

23

Vitamin A Excess

birth defects, (tetratogenic), blurred vision, liver damage
Osteoporosis, hypercalcemia

24

Vitamin A is derived from

carotenoids
plant pigments
b-carotene
-three forms - alcohol, aldehyde and acid

25

Find Vitamin A in

green, leafy vegetables
colored veggies
organ meat - liver

26

Why is beta carotene a safer source?

conversion to Vit A in gut decreases as dose increases
Absorption depends on type of food and how much fat is also in diet

27

How is Vitamin A taken up?

Retinol and carotenoids bound in enterocyte to Carotene binding proteins
carried in blood by chylomicrons or albumin

28

How is vitamin A important for vision?

combines with opsin to form rhodoposin in rod and cone cells
impt for the shape and structure of the conjunctiva and the cornea as well
functions in cellular differentiation - RXR and RAR receptors

29

Xerophthalmia

damage to cornea
can occur with vitamin A deficiency

30

Accutane

oral vitamin A treatment for acne
not for pts who can get pregnant
causes birth defects

31

Excess Vitamin A

headache
nausea
skin irritation
pain in joints
Osteoporosis

32

RAE

retinol activity units

33

Vitamin A RDA

men - 900ug/day
women - 700ug/day

34

what are some world wide problems seen with Vitamin A deficiencies?

increased susceptibility to infection
blinds nearly 500,000 preschool aged children
worsens iron status, causing anemia
accompanies protein and Zinc malnutrition
chronic fat malabsorption, low fat intake

35

Rickets

in children
severe bone deforming disease from lack of Vitamin D
cured with sunlight/fish oil

36

Vitamin D

mixture of ergocalciferol (D2) and cholecalciferol (D3)
derived from cholesterol - synthesized in the skin

37

What is active form?

Calcitrol (1,25-dihyroxyvitamin D
liver converts D3 to 25-hydroxyvitamin D
then kidneys converts to 1,25-dihyroxyvitamin D

38

Function of Vitamin D

regulates Ca levels in body
increases Ca uptake from diet, decreases Ca loss in uring , facilitates release of Ca from bones
may also modulate inflammation/immune responses

39

Osteomalacia

Vit D deficiency in adults

40

Vitamin D RDA

10ug/day (about 2 liters of vit D fortified milk

41

Vitamin D excess

large excess can be lethal
leads to hypercalcemia - deposition of Ca in soft tissues)
there can be local tissue intoxication

42

Vitamin D deficiencies linked to

Type II diabetes, autoimmune disease and other chronic diseases - cardiovascular, cancer

43

Serum level of Vit D deficiency

less than 20 ng/mL

44

Vitamin K

group of 3 molecules
phylloquinones
k1 - phllyoquinone in green leafy veggies
k2 - menaquinone, made by bacteria in intestines
k3 - menadione, artificial

45

Functions of Vitamin K

required for post-translational modification of many proteins which bind Ca++ including blood coagulating proteins
cofactor for carboxylases which add gamma-carboxy group onto glutamates

46

vitamin K inhibitors

coumarin/warfarin
inhibit clotting

47

Coumarin

in low doses inhibits vitamin k epoxide reductase and vit K reductase
so depletes Vit K and inhibits enzymes requiring vit K
all these inhibited activities lead to blood clotting

49

Name the B vitamins

Thiamine (b1)
Riboflavin (b2)
Niacin (b3)
Pantothenic acid (B5)
Pyridoxine (pyridoxal, pyridoxamine) (b6)
Biotin (vitamin H)
Cobalamin (b12)
Folic acid

50

Thiamine functions

helps form/break C-C bonds
1. Oxidative decarboxylation - pyruvate and a-ketoglutarate DH
2. Transketolase in PPP - converts glucose to ribose for DNA synthesis

51

Thiamine deficiency

Beriberi
Insufficient ATP production, decreased synthesis of DNA, RNA, proteins, fatty acids
muscle tissue wasting
cardiovascular damage
CNS damage - confusion, loss of reflex
Edema
seen in chronic alcoholism
usually see in skin first

52

Wernicke syndrome

Thiamine deficiency
associated with chronic alcoholism
known as dry beriberi becomes wet when develop cardiac dilated hypermyopathy (loss of energy, fluid build up)

53

Severe Thiamine deficiency leads to

involves CNS
called Korsakoff encephalopathy (Wernicke-korsakoff syndrome) - leads to short term memory loss
irreversible

54

What predisposes people to WK syndrome when diet is thiamine deficient ?

mutation in transketolase

55

Riboflavin

heat stable but light sensitive
intense yellow-green fluorescence
Coenzyme in TCA cycle - FAD/FADH
cofactor for other enzymes, oxygenases, oxidoreductases
can carry 2 electrons
can store about 1-2 weeks worth

56

what inhibits Thiamine uptake?

Alcohol

57

Riboflavin deficiency

prolonged can lead to cracked lips, dark red tongue, dermatitis, normocytic anemia, confusion

58

Excess Riboflavin

no real effect
lost rapidly

59

Forms of Niacin

nicotinic acid (precursor to NAD and NADP) and nicotinamide
Active form is NAD (bound to ribose and ADP)

60

Niacin deficiency

Pellagra -fragile skin called Casal's necklace
corn is low in niacin and Trp
fatigue, headache, apathy, depression, memory loss, dementia, pigmented skin rash after sun exposure, vomiting, diarrhea

61

Trp metabolite in urine suggests deficiency in

Niacin

62

Niacin Equivalents NE

1 mg pure niacin or 60 mg trytophan
Men 16 mg NE/day
women 14

63

Hartnup disease

impairs Trp absorption can lead to niacin deficiency

64

Excess Niacin

Flushing, buring of face, arms and chest, stomach irritation
long term - liver damage, irreversible liver failure

65

Excess of what vitamin could be cholesterol lowering ?

Niacin
must be watched carefully though
acts via G protein coupled receptor, reduces lipolysis, free fatty acids, VLDLs

66

Pantothenic acid

component of CoA and acyl carrier protein
No RDA, no deficiencies, excess seen
hard to differentiate Pantothenate deficiency from other vit B deficiencies - skin problems, burning feet, digestive problems, dizziness

67

Pyridoxine

involved in transamination, decarboxylation
required for function of glycogen phosphorylase, synthesis of heme, y-aminobutyric acid

68

Pyridoxal Phosphate (PLP)

derived from B6
deficiency leads to dermatitis and disorders of protein metabolism
group for enzymes catalyzing reactions involving amino acid metabolism

69

Pyridoxine deficiencies

microcytic anemia, EEG abnormalites, epileptic seizures, depression, confusion, seborrheic dermatitis, maybe also platelet and clotting problems

70

Drugs that can create a PLP deficiency

penicillinamine or isozianid

71

Pyridoxine excess

peripheral neuropathy, derm lesions

72

Biotin

synthesized by gut bacteria
tightly binds to egg protein (avidin)
functions in carboxylase reactions in FA synthesis, essential for lipid metabolism, amino acid breakdown

73

Biotin deficiency

impaired glucose tolerance, mental dysfunction, nausea, anorexia, dermatitis
some anticonvulsants inhibit uptake

74

Cyanocobalamin - vit B12

conenzymes: methylcobalamin, adenosylcobalamin
most potent - 3ug/day
contains corrin ring system and a cobalt
only synthesized by some bacteria
participates in enzyme catalyzed molecular rearrangements, ribonucleotide reductase and methyl group transfers
regenerates FH4 from methyl folate, prevents folate deficiency

75

Vitamin B12 deficiency

-can cause long tern, permanent damage to myelin sheath, peripheral neuropathy
-Pernicious anemia - megaloblastic anemia due to lack of intrinsic factor secretion
-lead to elevated homocysteine levels which are linked to CVD due to interference with collagen maturation

76

B12 and folate

intimate interaction with folate
levels fall with folate
anemia, temporarily respond to folate tx masking the deficiency but has neuro consequences

77

B12 deficiency most common in

wealthier countries, among elderly, most prevalent in poorer populations

78

Metformin

impairs B12 uptake

79

Diagnosis of B12 deficiency

serum or plasma ~200 pg/ml

80

Excess B12

doesnt hurt

81

what deficiencies increase serum tHcy

folate
riboflavin
vitamin B6
B12
THF

82

Homocysteine

remove terminal Ch3 from methionine

83

conversion of homocysteine to Methionine

Tetrahydrofolate and B12

84

conversion of homocysteine to Cys

B6

85

Intrinsic Factor

secreted from parietal cells in response to hormone
B12 ONLY absorbed in intestines when complexed to IF
binds to specific receptor in the ileum

86

Pernicious anemia

megaloblastic anemia due to lack of intrinsic factor secretion
atrophy of mucosa, loss of secretion of gastric acid and IF

87

Liver stores B12 can last

6-10years

88

Folate

FH4 made from folate
major carrier of single carbon units
takes 1C from Ser, Gly, His, formaldehyde and formate
1C transferred to pyrimidine dUMP to form dTMP - vital for DNA synthesis
cooking destroys 90% in food

89

Folate deficiency

affects rapidly dividing cells - RBC, intestinal epithelium, fetal tissues
Fetal - neural tube defects

90

Megaloblastic anemia

caused by both folate and cobalamine deficiencies
due to thymidylate synthase deficiency
causes enlarged red and white blood cells - abnormal nuclear maturation - NOT enough DNA

91

oral contraceptives and anticonvulsants

impair absorption or increase the breakdown of folate

92

Single carbon transfers

THF transfers CH3 to B12 which adds that too Homocysteine to make methionine

93

Vitamins stored in the liver

B12
Folate