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Chapter-33 Fat Soluble Vitamins (A, D, E, K)

BOOK TITLE: Textbook of Biochemistry for Medical Students

Author
1. Vasudevan DM
2. S Sreekumari
3. Vaidyanathan Kannan
ISBN
9789350250167
DOI
10.5005/jp/books/11359_33
Edition
6/e
Publishing Year
2011
Pages
12
Author Affiliations
1. Faculty of Medicine, Amrita Vishwa Vidyapeetham, (Amrita University), Kochi, Kerala, Formerly Principal, College of Medicine, Amrita, Kerala; Formerly, Dean, Sikkim Manipal Institute of Medical Sciences, Gangtok, Sikkim, Amrita Vishwa Vidyapeetham (Deemed University), Cochin, Kerala, E-mail: dmvasudevan@aims.amrita.edu, PG Programs and Research College of Medicine, Amrita Institute of Medical Sciences, Kochi, Kerala, India, College of Medicine, Amrita Institute of Medical Sciences, Kochi, Kerala, India; Sikkim Manipal Institute of Medical Sciences, Gangtok, Sikkim, India
2. Jubilee Mission Medical College, Trissur, Kerala, Sree Gokulam Medical College and Research Foundation, Thiruvananthapuram, Kerala, India, Jubilee Mission Medical College and Research Institute, Thrissur, Kerala, India, Government Medical College, Thrissur and Thiruvananthapuram, Kerala, India; Sree Gokulam Medical College and Research Foundation, Thiruvananthapuram, Kerala, India; Jubilee Mission Medical College and Research Institute, Thrissur, Kerala, India
3. Amrita Institute of Medical Sciences, Kochi, Kerala, India, Pushpagiri Institute of Medical Sciences and Research Centre, Thiruvalla, Kerala, India, Believers Church Medical College and Hospital, Thiruvalla, Kerala, India
Chapter keywords

Abstract

Vitamin A is a fat-soluble vitamin whose active form is present only in animal tissues, but provitamin A (beta carotene) is present in plant tissues. Retinols are poly isoprenoid compounds with Vitamin A activity, having the b ionone ring system. Active forms of the vitamin A include; Retinol, Retinal, Retinoic acid. The two important isomers are all Trans retinal and 11-cis retinal. Vitamin A is transported with the help of Retinal Binding Protein and this retinal–RBP complex has specific receptors in various tissues. Rhodopsin is a membrane protein made up of opsin plus 11-cis retinal and it is important in the visual cycle. Rods are for dim light vision and cones for color vision. Decrease in number of cones/cone proteins lead to color blindness. Vitamin D is derived from 7 dehydrocholesterol by the action of UV rays. Vitamin D deficiency results in rickets and osteomalacia. Different types of rickets are; hypophosphatemic, vitamin D resistant, renal rickets, and end organ refractoriness to 1, 25 DHCC. Vitamin E is tocopherol. It is absorbed along with fats with the help of bile salts. It is transported as chylomicrons and stored in adipose tissue. Vitamin E is the most important anti-oxidant in tissues. Vitamin K compounds are naphthoquinone derivatives. They are absorbed in intestine along with chylomicrons. They are also synthesized by intestinal flora. Storage is in the liver and transported in plasma is along with beta lipoproteins. Vitamin K is involved in blood coagulation. Vitamin K is required for post-translational modification of coagulation factors.

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