Vitamini A
Fotokozani mwachidule
Vitamini A imaphatikizapo mavitamini A1 ndi A2. Mavitamini A1 ndi A2 ali ofanana mu kapangidwe kake) Retinol imatha kupangidwa kuchokera ku beta-carotene yochokera ku zomera. Pansi pa catalysis ya β-carotene-15, 15'-peroxide (biooxygenase) m'thupi, β-carotene ikhoza kusinthidwa kukhala mamolekyu awiri a retinaldehyde (ratinal), ndi retinaldehyde mu reductase. Imachepetsedwa kukhala retinol pansi pa mphamvu ya. Chifukwa chake, beta-carotene imadziwikanso kuti vitamini A.
Kapangidwe ka mankhwala
Vitamini A ndi ufa wachikasu wosalala kapena wopyapyala, wosasungunuka m'madzi ndi glycerine, ndipo umasungunuka m'zinthu zambiri zachilengedwe monga ma alcohols, ethers, hydrocarbons ndi halogenated hydrocarbons. Dzina la mankhwala la thupi la vitamini A - retinol ndi all-trance 3,7-dimethyl-9-(2,6,6-trimethyl-1-cyclohexene-1)-2,4,6,8-nontetraene-1-ol, yokhala ndi ma conjugated double bonds anayi pa unyolo wake wam'mbali.
Ntchito ndi zotsatira za thupi
Vitamini A ndi vitamini yosungunuka ndi mafuta, ndipo ntchito yake ya thupi makamaka imakhala mu mawonekedwe a retinoic acid. Carotene ndi gwero lofunika la vitamini A. Vitamini A yomwe imagwira ntchito kwambiri mu carotene ndi beta-carotene. Kuchuluka kwa kuyamwa m'matumbo a munthu ndi pafupifupi gawo limodzi mwa magawo asanu ndi limodzi a vitamini A. Vitamini A imasungidwa makamaka m'chiwindi m'thupi, yomwe imapanga pafupifupi 90% mpaka 95% ya kuchuluka konse, ndipo pang'ono imasungidwa mu minofu ya mafuta. Vitamini A imagwira ntchito yofunika kwambiri pa ntchito ya kagayidwe kachakudya m'thupi la munthu.
