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HUNT 241 > Lecture 2 - Folate > Flashcards

Lecture 2 - Folate Flashcards

1
Q

what is vitamin is folate

A

B9

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2
Q

what are food sources of folate

A
  • green leafy vegetables
  • orange juice
  • peanuts
  • legumes and beans
  • bread (mandatory fortified)
  • range of breakfast cereals (fortified)
  • liver
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3
Q

why is liver such an important source of folate

A

mammals store 50% of their folate in their liver, so consuming liver from animals is a useful source

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4
Q

what part of the folate molecule can humans not manufacture and what does this mean

A

the middle part

so therefore folate is essential in the diet

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5
Q

what is folic acid

A

being added when the food is fortified

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6
Q

what is food folate

A

naturally present in food

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7
Q

how is food folate chemical different to folic acid

A

methyl group is on food folate that isn’t on folic acid

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8
Q

where is folic acid usually found

A

supplements and food fortification

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9
Q

what is the name of the form of most food folate

A

methyltetrahydrofolate

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10
Q

what is meant by folic acid is a “pre vitamin”

A

needs to be reduced to active form of folate

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11
Q

what is the active form of folate

A

tetrahydrofolate

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12
Q

folic acid is in what form and why does this mean it is good to be used in fortification

A

fully oxidised form, it is quite stable and that is why it is used in fortification

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13
Q

is food folate polyglutamate or monoglutamate

A

polyglutamate

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14
Q

is folic acid polyglutamate or monoglutamate

A

monoglutamate

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15
Q

when are polyglutamates removed in absorption of folate

A

when it has entered the enterocyte

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16
Q

what helps more food folate into the cell

A

reduced folate carrier

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17
Q

what helps move folic acid into the cell

A

folate receptor

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18
Q

once both forms of folate are in the cell, what happens to keep them in the cell

A

both forms are polyglutamated

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19
Q

what is DHFR (dihydrofolate reductase) do

A

add on hydrogens (reduction reaction) to get folate to the active form

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20
Q

if converting from folic acid to the active form what has changed

A

hydrogens have been added

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21
Q

if converting from food folate to the active form what has changed

A

there has been removal of methyl group by enzymes

22
Q

what are functions of folate

A

DNA synthesis, DNA methylation, purines

23
Q

how is folate involved in DNA synthesis

A

when there is sufficient folate, dUMP is converted to dTMP and its thymine (one of the four nucleotide bases) is incorporated into DNA

24
Q

what happens to DNA synthesis when there is insufficient folate

A

dUMP is not converted to dTMP, and uracil is misincorperated into DNA

25
Q

purines are what nucleotide bases

A

A and G bases for nucleotides

26
Q

purines are also what

A

part of AMP and GMP, which are converted to ATP and GTP to use as energy currencies

27
Q

what does folate provide for DNA methylation and what is this used for

A

a methyl group which is used for epigenetic modification

28
Q

what is epigenetic modification

A

a critical process in control of gene expression and stabilisation of the genome

29
Q

how is folate linked to DNA methylation

A
  • tetrahydrofolate has a methyl group added to it
  • this gets converted to 5-methyltetrahydrofolate
  • then conversion to methionine, then to SAM
  • then number of steps to DNA methylation
30
Q

when is homocysteine formed

A

when the amino acid methionine is metabolised to cysteine

31
Q

what are the four possible fates of homocysteine

A
  1. reform s-adenosyl homocysteine (SAH)
  2. remethylation to form methionine
  3. degradation through transulfuration pathway
  4. leaks out of cell if intracellular concentration too high
32
Q

hyperhomocysteinemia is associated with increased risk of what

A

increased risk of CVD and thrombosis

33
Q

if there is not enough folic acid in the diet not enough what will be formed

A

not enough THF will be formed from folic acid

34
Q

if there is not enough 5-methyl THF then not enough what will be formed

A

not enough THF will be formed

35
Q

lacking 5-methyl THF means what for production of methionine

A

means you will not to be able to add on the methyl group to homocysteine to form methionine (stable compound)

36
Q

what is the stable compound that homocysteine is converted to

A

methionine

37
Q

if you are unable to form methionine because you are lacking in 5-methyl THF what will this mean

A

means you will have an increase in the homocysteine concentration and an increase in the SAH molecule as well

38
Q

why will homocysteine levels stay elevated if there is damage to the 5-methyl THF

A

you can not pump all of the homocysteine into SAH so will be left with higher levels of homocysteine

39
Q

a case study on 22 year old female student on a largely CHO diet but not vegetarian reported symptoms of tiredness and breathlessness on minimal exertion, what did she have and what was the reason

A

megaloblastic anaemia due to folate deficiency

40
Q

what are megaloblasts

A

really big compared to normal red blood cells, they are the immature form

41
Q

how is folate linked to meglaloblastic anaemia

A

you need folate to form the nucleotide bases to form DNA

  • without enough folate proper cell devision does not occur and there for formation of the red blood cell does not happen properly and it enters the circulation still containing its nucleus
42
Q

what is another effect of folate deficiency

A

neural tube defects

43
Q

what are the complications that come with neural tube defects

A

below the defect you will get abnormal nerve conduction, so you will have issues with motor and sensory control / function

44
Q

what are the two main types of neural tube defects and what are they

A

spina bifida (lesion on the spine)

anencephaly (not compatible with life)

45
Q

approximately how many cases of neural tube defects are there in NZ each year

A

approx 64

46
Q

what part of New Zealand has higher rates of neural tube defects

A

the north island

47
Q

what is the folate toxicity rates from naturally occurring folate in foods

A

no risk

48
Q

high folic acid intake may lead to

A
  • obscure vitamin B12 deficiency
  • leading to delay in diagnosis of neurological damage
49
Q

what is the upper limit of folate for fortified foods or supplements

A

1,000μg/day (adults)

50
Q

what is ministry of health recommendation of RDI and EAR of folate for adult men and women

A

EAR : 320μg/day

RDI : 400μg/day

51
Q

what is ministry of health recommendation of RDI and EAR of folate during pregnancy

A

RDI : 600μg/day

52
Q

why is it important to have fortification of food with folate (pregnancy)

A

~53% of pregnancies are unplanned so they will not be taking a supplement which is why food sources need to be fortified

HUNT 241 (19 decks)

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