Ivithamini A
Yazisa ngokufutshane
IVithamini A iquka iivithamini A1 kunye ne-A2. Iivithamini A1 kunye ne-A2 ziyafana ngesakhiwo) I-Retinol inokuveliswa kwi-beta-carotene efumaneka kwizityalo. Phantsi kwe-catalysis ye-β-carotene-15, 15'-peroxide (i-biooxygenase) emzimbeni, i-β-carotene inokuguqulwa ibe ziimolekyuli ezimbini ze-retinaldehyde (i-ratinal), kunye ne-retinaldehyde kwi-reductase. Incitshiswa ibe yi-retinol phantsi kwesenzo se. Ke ngoko, i-beta-carotene ikwaziwa njenge-vitamin A.
Iimpawu zekhemikhali
IVithamini A yikristale etyheli eqhekekileyo okanye umgubo wekristale, enganyibilikiyo emanzini nakwiglycerine, kwaye iyanyibilika kwiinyibilikisi ezininzi zezinto eziphilayo ezifana neealcohols, ii-ethers, iihydrocarbons kunye neehydrocarbons zehalogenated. Igama lekhemikhali lomzimba weVithamini A - i-retinol yi-all-trance 3,7-dimethyl-9-(2,6,6-trimethyl-1-cyclohexene-1)-2,4,6,8-nontetraene-1-ol, enezibopho ezi-4 ezidityanisiweyo kwikhonkco layo elisecaleni.
Imisebenzi kunye nemiphumo yefiziyoloji
IVithamini A yivithamini enyibilikayo emafutheni, kwaye umsebenzi wayo womzimba uninzi lwayo lukwimo ye-retinoic acid. ICarotene ngumthombo obalulekileyo weVithamini A. Eyona vithamini A esebenzayo kwi-carotene yi-beta-carotene. Izinga lokufunxwa emathunjini omntu limalunga nesinye kwisithandathu sevithamini A. IVithamini A igcinwa kakhulu kwisibindi emzimbeni, imalunga ne-90% ukuya kwi-95% yenani lilonke, kwaye inani elincinci ligcinwa kwizicubu zamafutha. IVithamini A idlala indima ebaluleke kakhulu kumsebenzi we-metabolic womzimba womntu.
