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LUDI Folate Acid and B12
Vitamins lectures
51
Dentistry
Undergraduate 2
04/18/2014

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Term
Vitamin definition
Definition
Organic molecules required in small amounts to maintain life. They are essential as they cannot be made by the human body.
Term
Fat soluble vitamins
Definition
A D E K
Term
Water soluble vitamins
Definition
C, B6, B12, Biotin, Folate, Niacin, Pantothenic acid, Riboflavin B2, Thiamin B1,
Term
Fate of excess water soluble vitamins
Definition
Excreted in urine
Term
Relative toxicity of water soluble
Definition
Less toxic generally than fat soluble
Term
Fate of excess FAT soluble vitamins
Definition
Accumulate in adipose tissue and can reach toxic levels
Term
What must be present in the diet for fat soluble vitamins to be absorbed?
Definition
Fat
Term
Which vitamin type takes longer to become deficient?
Definition
Fat
Term
Source of vitamin C
Definition
Fruits, vegetables and liver
Term
Function of vitamin c (3)
Definition
1. Antioxidant
2. Synthesis of biomolecules
3. Iron absorbtion
Term
Can vitamin c be stored?
Definition
No (It is water soluble)
Term
Vitamin C deficiency
Definition
Scurvy
Term
Symptoms of vit C deficiency (4)
Definition
1. Loose teeth
2. Poor healing
3. Fragility of blood vessels
4. Mild anaemia
Term
Amino acids involved with collagen synthesis?
Definition
Proline and Lysine
Term
What are proline and lysine converted to in collagen synthesis?
Definition
Hydroxyproline and Hydroxylysine
Term
What do the hydroxylase enzymes require for this process?
Definition
Fe2+
Term
What does vit C prevent occuring?
Definition
Prevents Fe2+ --> Fe3+
Term
Without vit C what does not properly form?
Definition
Hydrogen bonds between collagen chains
Term
Where is vitamin d made?
Definition
In the skin with the help of sunlight
Term
Relative toxicity of vit D?
Definition
Most toxic of all vitamins
Term
Why is exposure to sunlight needed?
Definition
Natural diets typically do not contain adequate quantities of vit D
Term
Which molecule is required from the liver as a precursor to Vit D?
Definition
7- dehydrocholesterol
Term
What happens to 7-dehydrocholesterol?
Definition
Ring cleavage to form inactive vitamin D
Term
What happens to inactive Vit D to activate it?
Definition
Two Hydroxylations
OH added to C1 and C25 to produce 1,25-dihydroxyvitamin D
Term
Folate (folic acid) source
Definition
green leafy vegetables, liver & nuts
Term
Folic acid function
Definition
Carrier of 1 carbon units
Term
Deficiency manifestations (3)
Definition
1. Megaloblastic anaemia hair loss
2. fatigue
3. birth defects (spina bifida)
Term
Symptoms of B group vitamin deficiency (folate is B vitamin) (3)
Definition
1. Glossitis
2. Recurrent apthous stomatits
3. Angular chelosis
Term
Why does folic acid need activating
Definition
Folic acid is not the active form of the vitamin. It needs reducing to tetrahydrofolate
Term
What is used as a reducing agent for folate?
Definition
NADPH
Term
What enzyme uses NADPH to as two hydrogens at a time to folate?
Definition
Dihydrofolate reductase
Term
How many times in folate reduced by dihydrofolate reductase?
Definition
Twice
Term
What is beneficial about dihydrofolate in microorganisms?
Definition
It is in a different form to human dihydrofolate so can be inhibited with drugs which have little effect on humans.
Term
Function of folic acid
Definition
Coenzyme in reactions involving the transfer of a 1 carbon unit to other compounts
Term
Which part of the tertrahydrofolate molecule carries the extra carbon?
Definition
N5, N10 or bridged between both
Term
Important example of tetrahydrofolate function
Definition
Synthesis of Deoxythymidylate (dTMP) which is the T base in DNA
Term
Methyl group + tetrahydrofolate in sythesis of deoxythidylate
Definition
N5, N10- methyltetrafolate
Term
For which types of cells in N5,N10-methyltetrahydrofolate important
Definition
Rapidly dividing cells which require lots of nucleic bases forming:
Bone marrow, hair follicles, cancer cells
Term
What production is inhibited in chemotherapy?
Definition
Deoxythymidylate (dTMP) production
Term
Drug used in chemotherapy?
Definition
Methotrexate
Term
How does methotrexate inhibit deoxythymidylate (dTMP) production?
Definition
Binds to folate reductase 1000x stronger than folate.
This inhibits conversion of dihydrofolate to tetrahydrofolate.
Reduces amount of N5,N10-methyltetrahydrofolate for deoxythymidylate production which limits DNA synthesis and prevent rapid cell division.
Term
What does the conversion of N5-methyltetrahydrofolate to tetrahydrofolate depend on?
Definition
Vitamin B12
Term
What happens if vitamin B12 is deficient?
Definition
N5-methyltetrahydrofolate will no be able to be converted back to tetrahydrofolate which causing the tetrahydrofolate to become 'trapped' as N5-methyltetrahydrofolate: a.k.a. the folate trap
Term
What can a vitamin B12 deficiency give the appearance of?
Definition
Folate deficiency due to the folate trap
Term
What is the danger of supplementing folate for a B12 deficiency?
Definition
Folate trap will still occur so neurological damage will get worse.
Term
Vitamin B12 source
Definition
Only produced by microorganisms
Term
Function of vitamin B12
Definition
required for folate metabolism
Term
What does B12 bind to, to allow absorption?
Definition
Glycoprotein intrinsic factor (I.F.) in the stomach secreted by the parietal cells.
Term
What happens to Vitamin B12-I.F. complex in the small intestine
Definition
Recognised by mucosal cells and absorbed in final section of intestine
Term
Beta Oxidation function of B12?
Definition
Required in conversion of propionyl CoA to succinyl CoA
Term
Manifestation of B12 deficiency in Beta Oxidation?
Definition
Methylmalonyl CoA accumulates and demyelinates nerve cells causing neurological damage
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