Dipolar Nature of Amino Acids

The pH of the medium primarily determines the predominant ionic form of an amino acid.

The zwitterion form of an amino acid has both a positive and a negative charge, resulting in a net charge of zero.

The isoelectric pH (IpH) is the pH at which an amino acid is electrically neutral, with balanced positive and negative charges.

<p>Nonpolar amino acids have isoelectric pH values close to 7, while basic amino acids have higher values and acidic amino acids have lower values.</p> Signup and view all the answers

<p>The COOH group can lose an H+ ion in solution, contributing to the formation of the negative COO- charge in the zwitterion.</p> Signup and view all the answers

<p>The two enkephalins differ in the amino acid at the carboxyl end of the peptide chain.</p> Signup and view all the answers

<p>Bradykinin is partly responsible for triggering pain and lowering blood pressure.</p> Signup and view all the answers

<p>The first step in protein sequencing is hydrolysis, which can be performed using acid, alkali, or enzymes.</p> Signup and view all the answers

<p>Acid hydrolysis typically involves heating in the presence of 6N HCl at 110 °C for 10 to 100 hours.</p> Signup and view all the answers

<p>After hydrolysis, the next step is the identification of the products of hydrolysis.</p> Signup and view all the answers

<p>The C-terminal end contains a free carboxyl group and is where amino acids are added by forming peptide bonds.</p> Signup and view all the answers

<p>Peptides are named starting with the N-terminal amino acid, using the suffix -yl for each amino acid except the C-terminal amino acid, which retains its full name.</p> Signup and view all the answers

<p>Peptide bonds have partial double bond character, making them rigid and planar, which helps maintain the structure of proteins critical for their function.</p> Signup and view all the answers

<p>Both amino acids in aspartame must be in the L-form for it to be sweet; other forms lead to a bitter taste.</p> Signup and view all the answers

<p>Glutathione is composed of Glu-Cys-Gly and functions as an antioxidant, regulating oxidation-reduction reactions.</p> Signup and view all the answers

<p>In glutathione, Glu is bonded to Cys through the side-chain carboxyl group rather than the α-carbon carboxyl group.</p> Signup and view all the answers

<p>Peptide bonds are covalent and stable, not directly influenced by salt concentration or changes in pH.</p> Signup and view all the answers

<p>Almost all peptide bonds have a trans configuration, where the two adjacent α-carbons lie opposite to each other, contributing to the planar structure.</p> Signup and view all the answers

<p>Alkaline hydrolysis destroys arginine, cysteine, threonine, and serine, and partially deaminates some amino acids.</p> Signup and view all the answers

<p>Exopeptidases cleave external peptide bonds at either the N-terminal or C-terminal ends, allowing for the identification of liberated amino acids sequentially.</p> Signup and view all the answers

<p>Intermolecular hydrogen bonds between protein chains govern the formation of the beta-pleated sheet structure.</p> Signup and view all the answers

<p>Sanger's method uses dinitrofluorobenzene to label the N-terminal, while Edman's method utilizes phenylisothiocyanate to produce a phenylthiohydantoin compound.</p> Signup and view all the answers

<p>Tryptophan remains intact during alkaline hydrolysis, while it is completely destroyed in acid hydrolysis.</p> Signup and view all the answers

<p>In parallel structures, chains run in the same direction, while in antiparallel structures, chains run in opposite directions.</p> Signup and view all the answers

<p>It allows researchers to determine the relative concentrations and sequences of amino acids released during hydrolysis.</p> Signup and view all the answers

<p>Supersecondary structures refer to combinations of alpha-helices and beta-pleated sheets.</p> Signup and view all the answers

<p>The tertiary structure determines the overall three-dimensional shape of the protein, defining its biological function.</p> Signup and view all the answers

<p>Cysteine and arginine are released simultaneously in equal amounts.</p> Signup and view all the answers

<p>Aminopeptidases sequentially cleave peptide bonds starting from the N-terminal end of the polypeptide.</p> Signup and view all the answers

<p>Salt linkages, hydrogen bonds, disulfide bonds, hydrophobic bonds, van der Waals forces, and polar interactions with water.</p> Signup and view all the answers

<p>Proteins undergo hydrolysis, but certain amino acids like arginine, cysteine, and threonine are destroyed.</p> Signup and view all the answers

<p>Salt linkages form between positively and negatively charged side chains, contributing to protein stability.</p> Signup and view all the answers

<p>Fibrous proteins provide structural strength, while globular proteins are involved in transport, regulatory functions, and enzymatic activity.</p> Signup and view all the answers

<p>The extensive hydrogen bonding and regular arrangement of chains in beta-pleated sheets lead to crystallinity and low solubility.</p> Signup and view all the answers