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The tertiary structure is the product of the interaction between the side chains (R) of the amino acids composing the protein. Some of them contain positively or negatively charged groups, others are polar, and still others are nonpolar. The number of carbon atoms in the side chain varies from zero in glycine to nine in tryptophan. Positively…

The nitrogen and carbon atoms of a peptide chain cannot lie on a straight line, because of the magnitude of the bond angles between adjacent atoms of the chain; the bond angle is about 110°. Each of the nitrogen and carbon atoms can rotate to a certain extent, however, so that the chain has a limited flexibility. Because all of the amino acids,…

Primary structure Analytical and synthetic procedures reveal only the primary structure of the proteins—that is, the amino acid sequence of the peptide chains. They do not reveal information about the conformation (arrangement in space) of the peptide chain—that is, whether the peptide chain is present as a long straight thread or is irregularly coiled and folded into a globule. The configuration,…

Since each protein molecule consists of a long chain of amino acid residues, linked to each other by peptide bonds, the hydrolytic cleavage of all peptide bonds is a prerequisite for the quantitative determination of the amino acid residues. Hydrolysis is most frequently accomplished by boiling the protein with concentrated hydrochloric acid. The quantitative determination of the amino acids is…

The physicochemical properties of a protein are determined by the analogous properties of the amino acids in it. The α-carbon atom of all amino acids, with the exception of glycine, is asymmetric; this means that four different chemical entities (atoms or groups of atoms) are attached to it. As a result, each of the amino acids, except glycine, can…

The amino acids present in proteins differ from each other in the structure of their side (R) chains. The simplest amino acid is glycine, in which R is a hydrogen atom. In a number of amino acids, R represents straight or branched carbon chains. One of these amino acids is alanine, in which R is the methyl group (―CH3). Valine, leucine, and isoleucine, with longer R groups, complete the alkyl side-chain series.…

The amino acid composition of proteins The common property of all proteins is that they consist of long chains of α-amino (alpha amino) acids. The general structure of α-amino acids is shown in . The α-amino acids are so called because the α-carbon atom in the molecule carries an amino group (―NH2); the α-carbon atom also carries a carboxyl group…

Proteins are essential for life and are essential for a wide range of cellular activities. Protein enzymes catalyze the vast majority of chemical reactions that occur in the cell. Proteins provide many of the structural elements of a cell, and they help to bind cells together into tissues. Proteins, in the form of antibodies, protect animals from disease, and many hormones are proteins. Proteins…

Proteins are not stored for later use in animals. When an animal consumes excess proteins, they are converted into fats (glucose or triglycerides) and used to supply energy or build energy reserves. If an animal is not consuming sufficient protein, the body begins to break down protein-rich tissues, such as muscles, leading to muscle wasting and eventually death if…