Vitamin A
This form of vitamin A is the chromophore in rhodopsin, required for night vision.
Answer: What is 11-cis-retinal?
The provitamin in skin that UVB light converts to vitamin D₃.
Answer: What is 7-dehydrocholesterol?
The most biologically active form of vitamin E
Answer: What is α-tocopherol?
The form of vitamin K found in green leafy vegetables.
Answer: What is phylloquinone (K1)?
This protein escorts retinol inside enterocytes, making it soluble and directing it toward esterification by LRAT.
Answer: What is CRBP2 (cellular retinol-binding protein type 2)?
The main storage site for vitamin A in the body.
Answer: What is the liver (hepatic stellate cells)?
The two organs that sequentially hydroxylate vitamin D to its active form.
Answer: What are the liver and kidney?
The organ that selectively incorporates α-tocopherol into VLDL for circulation.
Answer: What is the liver?
The enzyme for which vitamin K serves as a cofactor, enabling carboxylation of glutamate residues.
Answer: What is γ-glutamyl carboxylase?
1,25-(OH)₂D increases expression of this apical calcium transporter in intestinal epithelial cells, initiating transcellular calcium absorption.
Answer: What is TRPV6?
Without retinoic acid, epithelial mucous-secreting cells are replaced by these.
Answer: What are keratinized squamous cells?
The enzyme in the kidney stimulated by PTH that produces calcitriol.
Answer: What is 1α-hydroxylase?
Over 90% of vitamin E is stored in this tissue.
Answer: What is adipose tissue?
The proteins in coagulation that require vitamin K-dependent carboxylation.
Answer: What are prothrombin (II), VII, IX, X, proteins C, S, Z?
The hydroxylation of vitamin D in the liver and kidney requires this mineral as a cofactor for the cytochrome P450 enzymes involved.
Answer: What is magnesium?
The trimolecular complex that transports retinol in the blood contains retinol-binding protein, transthyretin, and this thyroid hormone.
Answer: What is T4 (thyroxine)?
In the intestine, calcitriol increases transcription of this calcium-binding protein.
Answer: What is calbindin?
High-dose vitamin E supplementation increases the risk of this condition.
Answer: What is bleeding/hemorrhagic stroke?
Newborns receive vitamin K shots to prevent this disease.
Answer: What is hemorrhagic disease of the newborn?
This vitamin K–dependent protein, found in bone, prevents vascular and soft tissue calcification by binding calcium.
Answer: What is matrix Gla protein (MGP)?
This eye condition results from failure to regenerate 11-cis-retinal.
Answer: What is night blindness?
Toxicity from oral vitamin D usually requires this approximate chronic dose.
Answer: What is 50,000 IU/day for several months?
A rare neurodegenerative disease caused by mutations in α-TTP that prevents vitamin E transport.
Answer: What is Ataxia with Vitamin E Deficiency (AVED)?
Warfarin acts by inhibiting this enzyme, blocking vitamin K recycling.
Answer: What is Vitamin K epoxide reductase?
Retinoic acid regulates transcription by binding to RAR/RXR and altering chromatin. These two specific enzyme classes modify histones to either activate or repress transcription.
Answer: What are HATs (histone acetyltransferases) and HDACs (histone deacetylases)?