Thiamin, Pantothenic Acid, Biotin

Thiamin

Vitamin B1 essential for energy metabolism, part of Kreb's Cycle, contains pyrimidine ring and thiazole moiety.

Niacin

Vitamin B3, works alongside thiamin and riboflavin in the Kreb's Cycle.

Riboflavin

Vitamin B2, works alongside thiamin and niacin in the Kreb's Cycle.

Kreb's Cycle

Metabolic pathway for ATP production, involving thiamin, niacin, and riboflavin.

Pyrimidine ring

Part of thiamin's structure, involved in energy metabolism.

Thiazole moiety

Part of thiamin's structure, involved in energy metabolism.

Methyl group

Found in the thiazole ring of thiamin, serves as the active site during enzyme interaction.

Enzymes

Biological catalysts, often requiring thiamin for activation.

Thiamin sources

Found in meat, whole grains, legumes, and yeast

frequently enriched in grain products.

Thiamin sensitivity

Sensitive to high temperatures and alkaline pH, protected by reducing reagents like vitamin C and citric acid.

Thiamin absorption

Only free form can be absorbed, phosphorylated forms must be dephosphorylated by intestinal phosphatases.

Thiamin storage

Absorbed into blood, taken up by the liver, phosphorylated to coenzyme form TDP/TPP.

TDP/TPP

Most metabolically active form of thiamin, involved in energy metabolism and coenzyme function.

Thiamin functions

Energy metabolism, pentose and NADPH synthesis, membrane and nerve conduction.

Decarboxylase reactions

Essential for energy transformation, involve TDP/TPP and specific enzymes like pyruvate dehydrogenase.

Pyruvate dehydrogenase

Enzyme complex involving TDP/TPP, responsible for converting pyruvate to acetyl CoA.

Transketolase

Enzyme involved in pentose phosphate pathway, loosely binds to TDP/TPP.

Thiamin in nerve conduction

TTP plays a role in nerve conduction, activates chloride transport and stimulates nerve impulses.

Thiamin deficiency

Uncommon in developed world, can occur in alcoholism, liver damage, and diseases impairing absorption.

Maple syrup urine disease

Genetic disease related to thiamin status, results in accumulation of branched-chain amino acids and keto acids in the blood.

Thiamin toxicity

Parenteral exposure can cause headaches, cardiac arrhythmia, and convulsions.

Thiamin assessment

Measured by urinary thiamin concentrations and red blood cell transketolase activity.

Pantothenic acid

Vitamin B5, metabolically active form of coenzyme A, comprised of beta-alanine and D-pantoic acid.

Pantothenic acid sources

Found in various foods, including brewer's yeast, corn, cauliflower, kale, egg yolk, organ meats, milk, and whole-grain breads.

Pantothenic acid digestion

Hydrolyzed to free form before absorption through the enterocytes.

Pantothenic acid absorption

Absorbed via sodium-dependent active multivitamin carrier in the jejunum.

Pantothenic acid functions

Carries out acetyl and acyl transfer reactions, important for macronutrient and lipid metabolism.

Biotin

Vitamin B7, composed of ureido and tetrahydrothiophene rings with a valeric acid side chain.

Biotin sources

Found in meat products, soybeans, cereal products, and synthesized by intestinal bacteria.

Biotin digestion and absorption

Requires digestion prior to absorption, absorbed in the small intestine via passive diffusion or carrier-mediated transport.

Biotin functions

Covalently attaches to carboxylases, regulates gene expression, and plays a role in cellular division.

Biotin deficiency

Can occur due to impaired absorption, inflammatory bowel diseases, alcoholism, or genetic mutations in biotin-dependent enzymes.

Biotin toxicity

No reported toxic side effects, used in large amounts in skin and hair products.

Biotin assessment

Blood and urine analysis, decreased urinary biotin excretion and greater excretion of 3-hydroxy isovaleric acid are markers of deficiency.