Biochemistry, 4th Edition P14. 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. | 5 Proteins Their Primary Structure and Biological Functions ESSENTIAL QUESTIONS Proteins are polymers composed of hundreds or even thousands of amino acids linked in series by peptide bonds. What structural forms do these polypeptide chains assume how can the sequence of amino acids in a protein be determined and what are the biological roles played by proteins Although helices sometimes appear as decorative or utilitarian motifs in manmade structures they are a common structural theme in biological macromolecules proteins nucleic acids and even polysaccharides. Proteins are a diverse and abundant class of biomolecules constituting more than 50 of the dry weight of cells. Their diversity and abundance reflect the central role of proteins in virtually all aspects of cell structure and function. An extraordinary diversity of cellular activity is possible only because of the versatility inherent in proteins each of which is specifically tailored to its biological role. The pattern by which each is tailored resides within the genetic information of cells encoded in a specific sequence of nucleotide bases in DNA. Each such segment of encoded information defines a gene and expression of the gene leads to synthesis of the specific protein encoded by it endowing the cell with the functions unique to that particular protein. Proteins are the agents of biological function they are also the expressions of genetic information. What Architectural Arrangements Characterize Protein Structure Proteins Fall into Three Basic Classes According to Shape and Solubility As a first approximation proteins can be assigned to one of three global classes on the basis of shape and solubility fibrous globular or membrane Figure . Fibrous proteins tend to have relatively simple regular linear structures. These proteins often serve structural roles in cells. Typically they are insoluble in water or in dilute salt solutions. In contrast globular proteins are roughly spherical in shape. .
