Overview
This lecture covers the functions, sources, deficiencies, and toxicity of three B vitamins: pantothenic acid (B5), vitamin B6 (pyridoxine), and biotin (B7).
Pantothenic Acid (B5)
- Pantothenic acid is widespread in foods; deficiencies are rare.
- The primary role is synthesizing coenzyme A, which is crucial for metabolic reactions.
- Coenzyme A is essential for acetyl-CoA production, steroid hormone synthesis, and cholesterol metabolism.
- Unprocessed foods (whole grains, nuts, legumes) are richer sources, but it is present in cooked foods too.
Vitamin B6 (Pyridoxine)
- Vitamin B6 is involved in protein metabolism, notably the synthesis of amino acids via transamination.
- The active coenzyme form is PLP (pyridoxal phosphate).
- B6 aids the nervous and immune systems and supports hemoglobin synthesis.
- Deficiency can cause anemia, inflamed mouth and skin, and is possible in malnutrition or alcoholism.
- Protein-rich foods are primary sources; some dense plant sources exist.
- Excess B6 can cause nerve damage (toxicity).
- Supplemental B6 for PMS, morning sickness, or carpal tunnel is not strongly supported by research.
Biotin (B7)
- Biotin acts as a coenzyme in metabolism of carbs, fats, and proteins.
- It facilitates formation of oxaloacetate, amino acid breakdown, and fatty acid synthesis.
- Biotin deficiency is rare due to its wide presence in foods and synthesis by gut bacteria.
- Whole grains and protein foods are good sources.
- Consuming raw egg whites can cause deficiency due to avidin binding to biotin; cooking deactivates avidin.
- Deficiency may cause skin inflammation, hair loss, and neurological problems.
- Toxicity is rare; up to 200 mg/day is considered safe for potential hair/nail health benefits.
Key Terms & Definitions
- Pantothenic Acid (B5) — a B vitamin crucial for making coenzyme A.
- Coenzyme A — a compound essential for metabolism of carbs, fats, and proteins.
- Vitamin B6 (Pyridoxine) — B vitamin involved in protein and amino acid metabolism.
- Transamination — transfer of an amino group to create new amino acids.
- PLP (Pyridoxal Phosphate) — active coenzyme form of B6.
- Biotin (B7) — B vitamin acting as a coenzyme in major metabolic pathways.
- Avidin — a protein in raw egg whites that binds and inhibits biotin absorption.
Action Items / Next Steps
- Review chapter sections on folate and B12 for the next lecture.
- Know key functions, sources, and deficiency symptoms for each vitamin discussed.