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HUNT241 > Nutrition Lecture 2: Folate > Flashcards

Nutrition Lecture 2: Folate Flashcards

1
Q

What are rich food sources of folate?

A

Green leafy vegetables, orange juice, lentils, beans, fortified bread and cereals, liver - 1 cup spinach = 40% RDI

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2
Q

How many parts is the basic structure of folate?

A

3 parts

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3
Q

What are the 3 parts of the folate structure?

A
  1. Double ringed pteridine structure
  2. P-aminobenzoic acid (PABA)
  3. A glutamate
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4
Q

Why is folate an essential nutrient?

A

Humans cannot make p-aminobenzoic acid nor can we join together these three molecules. Therefore it is essential to get folate from the diet, an essential nutrient, a vitamin

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5
Q

What is the difference between folic acid and folate?

A

Folic Acid = added when there is a fortification
Food Folate = naturally present in food

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6
Q

How do the structures differ between folic acid and food folate?

A

There is a methyl group on the food folate, not on the folic acid.
There are 4 hydrogens added onto the food folate.

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7
Q

What is the chemical name for food folate?

A

MTHF “methyltetrahyrdofolate”

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8
Q

Where is folic acid found?

A

In supplements and food fortification

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9
Q

Why do we use folic acid instead of food folate for fortification?

A

Folic acid is folate in its fully oxidized form, which means it is quite stable

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10
Q

Do food folate and folic acid have the same carriers?

A

No they have different carriers to cross cell walls

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11
Q

What does it mean that folic acid is a pre-vitamin?

A

It needs to be reduced to its active form of folate

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12
Q

What is the active form of folate?

A

THF - tetrahydrofolate

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13
Q

What is GCP II?

A

Removes extra glutamates on dietary polyglutamates (food folate) so they can transported into cells in mono form

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14
Q

Where does GCP II happen?

A

In the gut lumen

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15
Q

What is RFC?

A

Reduced folate carrier

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16
Q

What is FR?

A

Folate receptor

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17
Q

What is the role of RFC?

A

Transports what was originally food folate through and into the cell - now in its mono form

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18
Q

What is the role of FR?

A

transports folic acid through and into the cell

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19
Q

What is FPGS?

A

Folylpolyglutamate synthase

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20
Q

What is the role of FPGS?

A

FPGS polyglutamates both forms of folate to keep them in the cells - no longer in mono form

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21
Q

What is the structure of THF?

A

Hydrogens have been added from folic acid. THF has a methyl group removed from food folate

22
Q

How is folate involved in our genetic material?

A

Folate is essential for DNA synthesis, production of purines and DNA methylation

23
Q

How does the process of folate producing a thymine work?

A

When there is sufficient folate, dUMP is converted to dTMP and its thymine is incorporated into DNA

24
Q

How is dUMP converted to dTMP?

A

DUMP binds methyl group from 5,10-MTHF to convert it to dTMP

25
Q

What enzyme transfers the methyl group from 5,10-MTHF to dTMP?

A

TS - thymidylate synthase

26
Q

What happens to DNA synthesis when there is insufficient folate?

A

dUMP is not converted to dTMP and uracil is misincorporated into DNA - uracil is incorperated instead of thymine

27
Q

What nucleotide bases are formed from THF?

A

Purines

28
Q

What are purines?

A

Adenine and Guanine

29
Q

What are the roles of Adenine and Guanine?

A
  1. Nucleotide bases in DNA and RNA
  2. Part of AMP and GMP
30
Q

What are AMP and GMP?

A

Activators that are converted into ATP and GTP to use as energy currencies

31
Q

How is folate involved in DNA methylation?

A

Folate provides the methyl group for DNA methylation

32
Q

What is DNA methylation used for?

A

Epigenetic modification

33
Q

What is epigenetic modification?

A

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

34
Q

What are the three main functions of folate?

A
  1. DNA synthesis
  2. Purines
  3. DNA methylation
35
Q

When is homocysteine formed?

A

When the amino acid methionine is metabolised to cysteine

36
Q

What is hyperhomocysteinemia associated with?

A

Increased risk of CVD and thrombosis

37
Q

What is hyperhomocysteinemia?

A

too high concentration of cysteine in the blood

38
Q

What are the four possible fates of homocysteine?

A
  1. Converted back to SAH
  2. Remethylated to form methionine
  3. Degradation, reduced into cystathionine
  4. If levels are too high will be released into blood
39
Q

What happens is there is not enough folic acid?

A

You won’t be able to form THF and eventually a build up of homocysteine

40
Q

What are symptoms of folate deficiency?

A

Tiredness, breathlessness = megaloblastic anaemia

41
Q

What is megaloblastic anaemia?

A

very large red blood cells and a decrease in the number of those cells

42
Q

What does folic acid reduce the risk of?

A

NTD - neural tube defects

43
Q

What are the two main types of NTD?

A
  1. Spina bifida
  2. Anencephaly
44
Q

What percent reductions in NTD’s in pregnancies with folic acid supplementation?

A

85% drop

45
Q

What are the risks of high folic acid intake?

A

May obscure B12 deficiency, could delay diagnosis of neurological damage

46
Q

Is there a risk of high food folate intake?

A

No risk

47
Q

What is the upper limit for folic acid?

A

1000ug/day (adults)

48
Q

What is the EAR for folate?

A

320ug/day

49
Q

What is the RDI for folate?

A

400ug/day

50
Q

What is the folate RDI for pregnant women?

A

600ug/day, if they are at risk for NTD this increases

HUNT241 (22 decks)

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