Amino Acids, Peptides, and Proteins | BC 351 - Principles of Biochemistry, Quizzes of Biochemistry

Download Amino Acids, Peptides, and Proteins | BC 351 - Principles of Biochemistry and more Quizzes Biochemistry in PDF only on Docsity! TERM 1 What are the normal components of a standard amino acid? DEFINITION 1 amino group, carboxyl group, a side chain (R group) TERM 2 What is not a normal components of a standard amino acid? DEFINITION 2 a methyl groupNot all amino acids have a methyl group bonded to the -carbon. Only alanine has a methyl group that is its side chain. In addition to having a side chain group, all amino acids have a carboxyl group, an amino group, and a hydrogen atom covalently bonded to the -carbon. TERM 3 L-alanine and D-alanine... DEFINITION 3 ...are The L- and D-stereoisomer forms of amino acids are enantiomers, which means that they are nonsuperimposable mirror images of each other. Alanine, like all amino acids beside glycine, has an -carbon atom to which four different groups are attached and therefore has a chiral center. Molecules with chiral centers have stereoisomers (e. g., L-alanine and D-alanine) that are enantiomers-isomers that are nonsuperimposable mirror images of each other. TERM 4 Cysteine residues play an important role in the structure of many proteins by... DEFINITION 4 ...providing covalent links between parts of a protein molecule or between two different protein chains.Disulfide bonds form by the oxidation of two cysteine residues on the same or different proteins chains. Disulfide bonds between Cys residues stabilize the structure of many proteins. TERM 5 Which amino acid (glycine, threonine, aspartate, arginine) has a net negative charge at pH 7.0? DEFINITION 5 aspartateAspartate (aspartic acid) has a negatively charged R group and is thus negatively charged at pH 7.0. TERM 6 Peptide bonds, which covalently link two amino acids, result from... DEFINITION 6 ...the condensation of amino acids.A peptide bond is formed by removal of the elements of water (dehydration) from the - carboxyl group of one amino acid with the -amino group of another. TERM 7 Which group or groups on a protein contribute most to its overall acid-base properties? DEFINITION 7 The R groups on the protein.The R groups on some amino acids, which are ionizable, vary most from protein to protein and thus contribute most to the overall acid-base properties of a protein. TERM 8 The level of protein structure that describes all aspects of the three-dimensional folding of a polypeptide is referred to as the... DEFINITION 8 ...tertiary structure. TERM 9 A protein retained on an affinity chromatography column is usually eluted off the column by... DEFINITION 9 ...adding the protein's free ligand.Affinity chromatography uses a specific ligand that is cross-linked to the column beads. After specific binding of a protein to its ligand on the column, the protein can be eluted from the column by adding a solution containing the protein's free ligand. TERM 10 Sodium dodecyl sulfate (SDS) is used in the electrophoresis of proteins to... DEFINITION 10 ...separate the subunits of a multisubunit protein.SDS, which is an ionic detergent, will disrupt the noncovalent bonds that allow the association between most subunits of a multisubunit protein. In addition, SDS binds proteins and contributes a large net negative charge, rendering the intrinsic charge of the protein insignificant and conferring on each protein a similar charge-to-mass ratio. This allows electrophoresis to separate proteins on the basis of their mass (molecular weight) rather than on their intrinsic charge.