UNIT 11: MICRONUTRIENDS III: Pantothenic Acid, Biotin, Folate, VitB12, VitB6

Question 1

What is Pantothenic acid?

Answer 1

aka vitamin B5
- water soluble vitamin
pantos = everwywhere
deficiency = rare

Question 2

What are the forms of pantothenic acid?

Answer 2

• free

- bound

Question 3

What is pantothenic acid converted to?

Answer 3

coenzyme A

Question 4

What forms 4-phosphopantetheine?

What is the purpose of this?

Answer 4

pantothenic acid + cysteine + phosphate (ATP)

• cofactor in fatty acid synthesis
• further metabolized to coenzyme A

Question 5

What is Biotin?

Answer 5

aka vitB7

- water soluble vitamin

Question 6

Raw eggs lead to ___>

Answer 6

biotin deficiency (biotin binding protein with raw egg)

Question 7

Biotin is found in what types of foods?

Answer 7

• bound to proteins

- not enough made by bacteria in humans

Question 8

What is biotin’s role as an enzyme cofactor?

Answer 8

transfers carboxylic functional group

Question 9

What are 3 reactions that involve carboxylation via biotin?

Answer 9

• pyruvate carboxylase (pyruvate –> oxaloacetate)
• acetylCoA carboxylase (acetylCoA –> malonylCoA)
• propionylCoA carboxylase (propprionylCoA –> methylmalonylCoA)

Question 10

What is folate?

Answer 10

aka vitB9

- water soluble vitamin

Question 11

What are sources of folate?

Answer 11

• folate = foliage = leafy greens

Question 12

What are sources of folic acid?

Answer 12

supplements and enriched breads, flours, corn meals, rice noodles etc.

Question 13

What is the difference between folate and folic acid?

Answer 13

folic acid comes from fortified/supplements –> pteroylmonoglutamates
folate comes from plants and animals –> pteroylpolyglutamates which is further broken down to pteroylmonoglutamates

Question 14

Which form of folate is absorbed?

Answer 14

pteroylmonoglutamate

• needs to be in this form/broken down to this before absorption
• this also makes folic acid more bioavailable since folate has more steps before absorption

Question 15

What is a major example of folate deficiency?

Answer 15

Neural Tube Defect

• neural tube forming in development, requires steady supply of folate
• deficiency can cause Spina Bifida

Question 16

What is Vitamin B12?

Answer 16

aka cobalamin (cobalt centre)
- water soluble vitamin

Question 17

What is the source of vitB12?

Answer 17

• originally from colonic bacteria (not absorbed by colon)
• stored: liver (up to 10 years)
• animal foods: fed with vB12 diet (fecal diet) (vegans risk deficiency)

Question 18

What is unique regarding vit B12 absorption?

Answer 18

• “intrinsic factor” chaperones B12 through GIT
• requires specific binding protein in small intestine for absorption
• receptor recognizes “intrinsic factor”-vitB12 complex
• receptor does not recognize vitB12 alone

Question 19

What other vitamin is vitB12 linked to?

Answer 19

folate (vitB9)

Question 20

VitB12 and folate are required for what process?

Answer 20

SAM cycle
DNA synthesis and repair
- Dietary folate caries N6-methyl group while vitB12 acts as a prosthetic gropu in methionine synthase (using N5-methylTHF)

Question 21

Folate deficiency leads to what in DNA synthesis?

Answer 21

• low dTMP, high dUMP
  = nucleotide pool imbalance
• slow DNA synthesis
• dUMP incorporated in DNA when it should not be
  = uracil misincorporation
  –> cancer

Question 22

B12 deficiency leads to:

Answer 22

• bone marrow impairment of DNA synthesis –> anemia
• RBC precursors cannot meet demands
• Neural tube defect same as folate

Question 23

What happens if you have a high folate diet but vitB12 deficiency?

Answer 23

• anemia does not occur
• DNA repair and synthesis is okay
• other symptoms!

Question 24

What is the toxicity of vitB12?

Answer 24

there is no toxicity

= no upper limit

Question 25

What is vitamin B6?

Answer 25

water soluble vitamin

Question 26

What are the forms of vitB6?

Answer 26

• pyridoxine
• pyridoxal
• pyridoxamine

phosphorylated and dephosphorylated = 6 forms of vit B6

Question 27

What is the main form of vitB6 in the blood?

Answer 27

phosphorylated pyridoxal = PLP

• blood
• bound to albumin

Question 28

What is the main form of vitB6 in plants?

Answer 28

pyridoxine

- converted to PLP

Question 29

What is the major storage site of vitB6?

Answer 29

muscle

Question 30

What are functions of vitB6

Answer 30

• transamination (protein metabolism)
• porphyrin synthesis (heme)
• neuroactive amines (EP/NE, serotonin, histamin, GABA)

Question 31

What happens if you have vitB6 deficiency?

Answer 31

rare

- anemia, convulsions, neuroactive amine metabolism

Question 32

What is the toxicity of vitB6?

Answer 32

• pain and numbness in extremities
• large TI
• difficult to achieve UL but exists