TAILIEUCHUNG - Biochemistry, 4th Edition P26

Biochemistry, 4th Edition P26. Continuing Garrett and Grisham's innovative conceptual and organizing framework, "Essential Questions," BIOCHEMISTRY guides students through course concepts in a way that reveals the beauty and usefulness of biochemistry in the everyday world. Streamlined for increased clarity and readability, this edition also includes new photos and illustrations that show the subject matter consistently throughout the text. New end-of-chapter problems, MCAT practice questions, and the unparalleled text/media integration with the power of CengageNOW round out this exceptional package, giving you the tools you need to both master course concepts and develop critical problem-solving skills you can draw upon. | Do Carbohydrates Provide a Structural Code 213 Proteoglycans Make Cartilage Flexible and Resilient Cartilage matrix proteoglycan is responsible for the flexibility and resilience of cartilage tissue in the body. In cartilage long filaments of hyaluronic acid are studded or coated with proteoglycan molecules as shown in Figure . The hyaluronate chains can be as long as 4 rm and can coordinate 100 or more proteoglycan units. Cartilage proteoglycan possesses a hyaluronic acid-binding domain on the NH2-terminal portion of the polypeptide which binds to hyaluronate with the assistance of a link protein. The proteoglycan-hyaluronate aggregates can have molecular weights of 2 million or more. The proteoglycan-hyaluronate aggregates are highly hydrated by virtue of strong interactions between water molecules and the polyanionic complex. When cartilage is compressed such as when joints absorb the impact of walking or running water is briefly squeezed out of the cartilage tissue and then reabsorbed when the stress is diminished. This reversible hydration gives cartilage its flexible shock-absorbing qualities and cushions the joints during physical activities that might otherwise injure the involved tissues. Do Carbohydrates Provide a Structural Code The surprisingly low number of genes in the genomes of complex multicellular organisms has led biochemists to consider other explanations for biological complexity and diversity. Oligosaccharides and polysaccharides endowed with an unsurpassed variability of structures are information carriers and glycoconjugates complexes of proteins with oligosaccharides and polysaccharides are the mediators of information transfer by these carbohydrate structures. Individual sugar units are the letters of the sugar code and the words and sentences of this code are synthesized by glycosyltransferases glycosidases and other enzymes. The total number of permutations for a six-unit polymer formed from an alphabet of 20 hexose .

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