Skildum: Vitamins Flashcards
Which cofactor is not required by the pyruvate dehydrogenase complex?
Biotin (carboxylation cofactor)
What are the fat soluble vitamins?
A, D, E, K
What is the biologically active form of vitamin A?
all trans retiniol
What are the structural elements of Vit A?
B-Ionine ring
branched polyunsaturated chain
alcohol
What can the alcohol of trans-retinol be converted to in the body?
aldehyde
carboxylic acid
ester w/ FA (palmitate)
What are the dietary forms of Vit A?
retinyl-acyl esters
carotenes (two molecules of retinol)
BOTH can be converted to all trans retinol
What is vit A found in?
Red, yellow, orange fruits and vegetables
*carrotts
What are lycopene, lutein, canthaxanthin?
Other forms of Vit A
What are the circulating forms of vit A?
carboxylic acid
retinoic acid
these are exported into the blood
What happens to the esterified retinoic acid esters?
Transfered into chylomicrons> enter the lymph system
What happens to retinoic acid that enters the blood?
Majority enters the liver (first organ that gets a crack at vits and nutrients)
What stores Vit A?
Vit A>
taken up by hepatocytes>
esterified to fat>
stored in stellate cells (enlarged stellate cells> vit A toxicity)
What mediates retiniol homeostasis in the body?
hepatocytes
What are the sources of retinyl to the hepatocytes?
dietary: chylomicrons
stored: stellate cells
Retinyl esters g out to…
Stellate cells (storage) VLDL (to tissues)
Retinol goes out to the serum in complex w/..
transthyretin
RBP
Retinoic acid goes out to the serum complexed to..
albumin
What are the functions of Vit A in the body?
Vision
Vit A def?
night blindness
Vit A toxicity?
blurred vision
How does light signaling through the eye reach neurons in the brain?
Rhodopsin (Opsin-cis-retinal)> Light> conversion to trans-retinal> activates heterotrimeric G protein> closure of Na channel> hyperpolarization of rod cell> signaling to neuron
Retinoic acid acts as a ligand for RAR, RXR and PPAR which act as…
activated TFs
What does retinoic acid as a transcription activator stimulate?
- differentiation of goblet cells (gut)–> affect absorption
- apoptosis of cancer cells (anti-cancer properities)
- maturation of dendritic cells
- recruitment of Ab secreting cells to small intestine
What does retinoic acid TFs inhibit?
keratinization