Vitamin A - Retinol

Question 1

vit. A is found in what

Answer 1

animal: liver, egg, milk
plant: yellow colored food

Question 2

where is carotenase found

Answer 2

carotenase found in intestines and liver

Question 3

what is the fate of retinylester in the liver

Answer 3

• retinylester to be stored
• retinol to be transported in blood
• retinol -> retinal -> retinoic acid

Question 4

biochemical role and deficiency; skin/mucosa

Answer 4

• division+keratinization of epithelial cell (transcription level)
• mucoprotein synthesis in mucosa
• –> abnormal keratinization, dryness of cornea and conjunctiva -> xerophtalmia
• –> skin, GI, airways, uterus, testis etc. will be damaged

Question 5

biochemical role and deficiency; bone

Answer 5

• chondroitinsulphate synthesis (-SO4)
• bone formation: growth factors, receptor production
• –> abnormal bone development

Question 6

biochemical role and deficiency; reproductive system

Answer 6

• pregnenolon -vit.A-> progesterone
• –> uterus, testis epithelium proliferation will be abnormal: fertilization problem. damage in oogenesis and spermatogenesis

Question 7

biochemical role and deficiency; visual function

Answer 7

11-cis retinal bound to proteins called opsins: chemical basis of animal vision. Retinal allows certain microorganisms to convert light into metabolic energy.
—-> difficult or impossible to see in relatively low light, night blindness = nyctalopia

Question 8

hypervitaminosis

Answer 8

• B-carotene can never cause hypervitaminosis, because it cannot be degraded to vit A if hypervitaminosis!
• storage of retinylester in liver can result in hypervitaminosis if its consumed in excess
• vitamin A is the main cause

Question 9

cattle metabolism of vit. A

Answer 9

B-carotene -chylomicron-> liver/follicles/mamm. gl. -> retinal ->

• retinoic acid
• retinol -> retinyl-ester