Water-Soluble Vitamins (Extensive)

Question 1

Folic Acid

Answer 1

• Other Names: Folate/B₉
• Function: key role in one-carbon metabolism (overlaps with B₁₂ & B₆):
• homocysteine to form methionine (can be converted to SAM, a universal methyl group donor)
• dUMP to form dTMP
• metabolites of de novo purine biosynthetic pathway to form AMP and GMP
• Absorption: ?
• Activation: Reduced in liver using NADPH + dihydrofolate reductase (*rxn inhibited by Methotrexate*) to active form
• Active/Coenzyme Form: tetrahydrofolate (N5-methyltetrahydrofolate predominant circulating form)
• Deficiency: Most common vitamin deficiency in the US (esp. pregnant women and alcoholics).
• Megaloblastic Anemia (decreased DNA synthesis in erythropoetic cells)
• Hyperhomocysteinemia (increased risk of coronary heart disease)
• Neural tube defects (spina bifida, anencephaly, excencephaly)
• Fatigue, acne, sore tongue and neuropathies
• Toxicity: X
• Dietary Source: Liver, egg yolk, orange juice and green vegetables
• Daily Allowance: 200 μg in adults & 400 μg-1mg during pregnancy and lactation

Question 2

Cobalamin

Answer 2

• Other Names: B₁₂
• Function:
• Absorption:
• Activation:
• Active/Coenzyme Form:
• Deficiency:
• Toxicity:
• Dietary Source:
• Daily Allowance:

Question 3

Ascorbate

Answer 3

• Other Names:
• Function:
• Absorption:
• Activation:
• Active/Coenzyme Form:
• Deficiency:
• Toxicity:
• Dietary Source:
• Daily Allowance:

Question 4

Biotin

Answer 4

• Other Names:
• Function:
• Absorption:
• Activation:
• Active/Coenzyme Form:
• Deficiency:
• Toxicity:
• Dietary Source:
• Daily Allowance:

Question 5

Thiamine

Answer 5

• Other Names:
• Function:
• Absorption:
• Activation:
• Active/Coenzyme Form:
• Deficiency:
• Toxicity:
• Dietary Source:
• Daily Allowance:

Question 6

Niacin

Answer 6

• Other Names:
• Function:
• Absorption:
• Activation:
• Active/Coenzyme Form:
• Deficiency:
• Toxicity:
• Dietary Source:
• Daily Allowance:

Question 7

Pyridoxine

Answer 7

• Other Names:
• Function:
• Absorption:
• Activation:
• Active/Coenzyme Form:
• Deficiency:
• Toxicity:
• Dietary Source:
• Daily Allowance:

Question 8

Riboflavin

Answer 8

• Other Names:
• Function:
• Absorption:
• Activation:
• Active/Coenzyme Form:
• Deficiency:
• Toxicity:
• Dietary Source:
• Daily Allowance:

Question 9

Pantothenic Acid

Answer 9

• Other Names:
• Function:
• Absorption:
• Activation:
• Active/Coenzyme Form:
• Deficiency:
• Toxicity:
• Dietary Source:
• Daily Allowance:

Question 10

General characteristics of water-soluble vitamins…

Answer 10

• Not absorbed with or dependent on lipids
• transported from small intestine via portal circulation
• excess not stored in any tissue (*exception*: B12/Cobalamin)
• Deficiency symptoms quick to develop
• Excess lost in urine– no toxicity (*exception*: B6/Pyridoxine)
• Derived from plant sources (*exception*: B12/cobalamin)
• Dietary requirement closely linked to metabolic rate