Water Soluble Vitamins

Question 1

Thiamine (B1)

Answer 1

→ active form: thiamine pyrophosphate (TRP)
1. Co-enzyme for TCA cycle stuff (pyruvate dehydrogenase)
2. Stores last only 1 month (can develop a quick deficiency)
3. Deficiency impairs TCA; lactic acid accumulates (↓pyruvate dehydrogenase activity);↓neurotransmitters; ↓HMP shunt activity &↓nuclei acid synthesis
4. Causes beriberi (dry & wet)
5. Polished rice diet can cause deficiency b/c covering is removed + Alcohol abuse reduces absorption & appetite
6. Whole grains, legume, meat, fish, eggs, nuts
7. Absorbed @ upper SI

Question 2

Riboflavin (B2)

Answer 2

→ FAD & FMN
1. Coenzyme in ETC, TCA, b - oxidation [succinate → fumarate using succinate dehydrogenase]
2. Can develop easy deficiency
3. Required to make B3 (nicotinamide) from tryptophan
4. Heat stable but destroyed by sunlight
5. Causes Riboflavin deficiency: (dermatitis, angular stomatitis, glossitis)
6. Milk, meat, green veg., whole grain

Question 3

Niacin (B3)

Answer 3

→ nicotinamide [NAD & NADP]
1. Coenzyme in ETC, b - oxidation, PDH, LDH, FA synthesis
2. Nicotinamide formed endogenously; requires B2 & B6
3. Reduces oxidative stress
4. Causes Pellagra: (diarrhoea, dermatitis, dementia, death)
5. Deficiency is due to:
→ caused by isoniazid (Vit. B6↓so Vit. B3↓)
→ carcinoid syndrome (overuse of tryptophan)
→ hartnup disease (↓tryptophan absorption so↓B2)
6. Meat, legume, whole grains

Question 4

Pantothenic acid ( B5)

Answer 4

1. Component of coenzyme A & acyl carrier proteins
2. Involved in transfer of acyl groups:
   → acetyl coA
   → acetoacetyl coA
   → fatty acyl coA
   → succinyl coA

Question 5

Pyridoxine / Pyridoxal (B6)

Answer 5

→ pyridoxal phosphate (PLP)
1. Coenzyme for aminotransferases, glycogen phosphorylase, ALA synthase
2. Deficiency due to isoniazid therapy (rare)

Question 6

Folate (B9)

Answer 6

→ tetrahydrofolate (TH4)
1. Transported in blood as methyltetrahydrofolate
2. Needed in purine synthesis, TMP synthesis to make more RBCs (most affected in deficiency)
3. Cause Megaloblastic anemia & Neural tube defects
4. Deficiency is due to:
→ B12 deficiency (folate trap)
→ pregnancy + lactation
→ dihydrofolate reductase (DHFR) inhibitors [methotrexate]
5. Dark green leafy veg., liver & kidneys, peas

Question 7

Cobolamine (B12)

Answer 7

→ methylcobolamin
1. Coenzyme for methionine synthase & methylmalonyl coA mutase
2. Needed for tetrahydrofolate synthesis; nucleic acid synthesis; SM synthesis; methylmalonyl coA → succinyl coA; myelination
3. Absorbed at terminal ileum (as a complex bound to intrinsic factor secreted by gastric parietal cells)
4. Causes Megaloblastic anaemia and Neurological features
5. Deficiency is due to:
→ vegan diet
→ pernicious anaemia (auto immune destruction of gastric parietal cells)
6. Fish, meat, eggs, milk

Question 8

Biotin

Answer 8

1. Coenzyme for carboxylase enzymes
2. Synthesized by microorganisms

Question 9

Vitamin C (ascorbic acid)

Answer 9

1. Needed as a reducing agent to keep Fe2+ and Cu2+ in their forms (b/c both are needed for enzymes)
2. Coenzyme for hydroxylase enzymes (prolyl hydroxylase, lysyl hydroxylase = for collagen synthesis)
3. Is a water soluble antioxidant
4. Needed for conversion of Fe3+ → Fe2+ !!!
5. Deficiency is due to:
   → scurvy (gum bleeding - due to↓collagen synthesis)
6. Fresh fruits (citrus), tomatoes, potatoes