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8 Cards in this Set

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what is the function of retinoic acid?
it is a ligand for nuclear hormone receptors that modulate txn (it is not converted to retinal or retinol in the body)
retinol is toxic in high doses, but beta carotene is not, why?
Cleavage of beta carotene to retinoids in insufficient in the body.
vitamin A is stored in the liver as...
retinyl palmitate
vitamin A deficiency can lead to what?
night blindness, and in the very young who consume no vit A->xeropthalmia and keratomalacia
rhodopsin is a GPCR with 11-cis retinal covalently linked to what amino acid at what transmembrane helix?
to lysine at 7th helix
What distinguishes rhodopsin as well as the three color opsin proteins from each other?
They are each connected to 11 cis retinal by different amino acids thus affecting color sensation.
what is the name of the G protein activated by the opsins and what does it activate?
transducin activates a PDE in the disk membrane that cleaves cGMP
How are cGMP levels re-raised after the PDE cleaves them?
Ca2+ continues to pump out of the hyperpolarized cell. Once Ca2+ is low enough guanylyl cyclase is activated and PDE is inactivated.