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Unformatted text preview: Cell Biology 3000 Tripp Jones notes Tuesday, August 19, 2008 • Proteins • Proteins make up most of the mass of cells dry mass • Proteins are large organic compound made of amino acids arranged in a linear chain and joined together by peptide bonds between the carboxyl and amino groups of adjacent amino acid residues. - Wikipedia • History of proteins • Proteins were recognized as a distinct class of biological molecules in the eighteenth century by Antoine Fourcroy and others, distinguished by the molecules' ability to coagulate or ¡occulate under treatments with heat or acid. Noted examples at the time included albumin from egg whites, blood, serum albumin, ¢brin, and wheat gluten. Dutch chemist Gerhardus Johannes Mulder carried out elemental analysis of common proteins and found that nearly all proteins had the same empirical formula. The term "protein" to describe these molecules was proposed in 1838 by Mulder's associate Jöns Jakob Berzelius. Mulder went on to identify the products of protein degradation such as the amino acid leucine for which he found a (nearly correct) molecular weight of 131 Da. The dif¢culty in purifying proteins in large quantities made them very dif¢cult for early protein biochemists to study. Hence, early studies focused on proteins that could be puri¢ed in large quantities, e.g., those of blood, egg white, various toxins, and digestive/metabolic enzymes obtained from slaughterhouses. In the late 1950s, the Armour Hot Dog Co. puri¢ed 1 kg (= one million milligrams) of pure bovine pancreatic ribonuclease A and made it freely available to scientists around the world. Linus Pauling is credited with the successful prediction of regular protein secondary structures based on hydrogen bonding, an idea ¢rst put forth by...
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