Collagen:
Collagen, the most abundant protein in mammalian tissues, accounts for up to one-third of all protein mass in a mammal. Collagen fibers form the matrix or cement material in human bones where bone mineral precipitate. Collagen fibers constitute a major part of tendons and act as a major part of skin. The main function of collagen is the mechanical reinforcement of the connective tissues of vertebrates .
The individual polypeptide chains of collagen contain 20 different amino acids and the precise composition varies between different tissues. The variation in specific amino acid sequence gives rise to the different types of collagen labeled as Type I , Type II up to Type XIX. The most commonly occurring collagens are Types I , and M, which form the long-recognized characteristic fiber bundles seen in many tissues. Type I collagen is mostly found in skin, tendon, and bone, and Type HI in blood vessels. The various collagen types show differences in degrees of glycosylation, which means that glucose and galactose are covalently coupled to the collagen molecules .
The basic building block of collagen is a triple helix of three polypeptide chains called the tropocollagen unit. Each chain is about 1,000 amino acid residues long. These three individual a-chains are cross-linked biosynthetically and fold to form a triple helix (tertiary structure) with a molecular weight of approximately 300.000 g/mol, a length of approximately 300 nm and a diameter of 1. 5 nm .
المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .
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