Biochemistry: Vitamins & Cofactors

Vocabulary practice flashcards covering water-soluble and fat-soluble vitamins, coenzymes, deficiencies, structure, and metal cofactors.

Vitamin

An organic or organometallic compound essential for the proper functioning of the body that cannot be synthesized in adequate amounts by human cells and must be obtained through dietary sources.

Water-Soluble Vitamins

A class of vitamins that includes Vitamin C and the B-complex vitamins, which generally act as precursor molecules for enzyme coenzymes and are excreted when present in excess.

Fat-Soluble Vitamins

A class of vitamins including Vitamins A, D, E, and K that are hydrocarbon-like with few functional groups, are involved in plasma membrane processes, and do not serve as coenzymes.

Ascorbic Acid (Vitamin C)

A water-soluble noncoenzyme antioxidant vitamin involved in collagen formation and amino acid metabolism, where tissue saturation occurs at $100\,\text{mg/day}$ and deficiency causes scurvy.

Thiamine (Vitamin B1)

A water-soluble B vitamin converted by TPP synthetase into thiamine pyrophosphate (TPP); deficiency leads to beriberi.

Thiamine Pyrophosphate (TPP)

A coenzyme derived from vitamin B1 (thiamine) that catalyzes aldehyde transfer reactions and the synthesis or cleavage of bonds to carbonyl carbons in carbohydrate metabolism.

Riboflavin (Vitamin B2)

A water-soluble B vitamin that serves as the precursor for FMN and FAD coenzymes; its deficiency causes ariboflavinosis, cheliosis, angular stomatitis, and dermatitis.

Flavin Adenine Dinucleotide (FAD)

An electron-carrying prosthetic group and coenzyme derived from vitamin B2 (riboflavin) that functions in oxidation-reduction reactions, such as those catalyzed by pyruvate dehydrogenase.

Niacin (Vitamin B3)

Also known as nicotinic acid, a water-soluble vitamin that serves as the precursor for NAD+ and NADP+; deficiency results in pellagra.

Nicotinamide Adenine Dinucleotide (NAD+)

An oxidation-reduction coenzyme derived from niacin (vitamin B3) involved in electron transfer reactions, such as the conversion of ethanol to acetaldehyde by alcohol dehydrogenase.

Pantothenic Acid (Vitamin B5)

A water-soluble B vitamin required for the formation of Coenzyme A, which functions in acyl-group transfer reactions; deficiency can cause paresthesia and hypertension.

Pyridoxine (Vitamin B6)

A water-soluble B vitamin that forms pyridoxal 5'-phosphate (PLP), a coenzyme essential for amino acid synthesis and group transfer reactions to or from amino acids.

Pyridoxal 5'-phosphate (PLP)

The active coenzyme form of vitamin B6 (pyridoxine) containing a phosphate group attached to pyridoxal, involved in group transfer reactions of amino acids.

Biotin (Vitamin B7)

A water-soluble B vitamin that functions as a coenzyme for ATP-dependent carboxylation and carboxyl-group transfer when covalently attached to a carrier protein as a biotin-lysine adduct.

Folic Acid (Vitamin B9)

A water-soluble B vitamin converted into the coenzyme tetrahydrofolate (THF), which transfers one-carbon components and participates in thymine synthesis; deficiency causes neural-tube defects and anemia.

Cyanocobalamin (Vitamin B12)

A water-soluble cobalt-containing vitamin essential for forming adenosylcobalamin and methylcobalamin coenzymes; deficiency leads to pernicious anemia, anemia, and methylmalonic acidosis.

Retinol (Vitamin A)

A fat-soluble retinoid derived from β-carotene with key roles in vision, growth, and reproduction; deficiency leads to night blindness and cornea damage.

α-Tocopherol (Vitamin E)

A fat-soluble antioxidant vitamin featuring an $-OH$ group to donate hydrogen atoms to free radicals and a hydrophobic side chain to insert into biological membranes.

Calciferol (Vitamin D)

A fat-soluble vitamin made in skin via UV light action on 7-dehydrocholesterol that regulates calcium and phosphate homeostasis, with 1,25-dihydroxycholecalciferol as its active form; deficiency causes rickets in children and osteomalacia in adults.

Vitamin K

A group of fat-soluble compounds (phylloquinone K1 and menaquinones K2) that facilitates blood coagulation by aiding posttranslational modifications required to form prothrombin.

Choline

A water-soluble essential nutrient structured as a quaternary amine cation that serves as a constituent head group in membrane phospholipids like phosphatidylcholine and sphingomyelin.

Phosphatidylcholine

A phospholipid containing a choline cation head group that forms a major structural building block in biological membranes of non-nerve cells.

Sphingomyelin

A lipid containing a choline cation head group that serves as a major structural component in the biological membranes of nerve and brain cells.

Beriberi

A deficiency disease caused by a lack of vitamin B1 (thiamine) characterized by weight loss, heart problems, and neurological dysfunction.

Pellagra

A deficiency disease caused by a lack of vitamin B3 (niacin/nicotinic acid), characterized by dermatitis, depression, and diarrhea.

Scurvy

A deficiency disease caused by a lack of vitamin C (ascorbic acid), presenting with swollen and bleeding gums and subdermal hemorrhaging.

Trace Elements

Essential metal ions required in very small quantities that act as inorganic cofactors for specific enzymatic reactions.