Biochem ACS Review Test Questions and Answers Top Graded 2024

What amino acids have nonpolar, aliphatic R groups? - Glycine, Alanine, Proline, Valine, Leucine, Isoleucine, Methionine What amino acids have polar, uncharged R groups? - Serine, Threonine, Cysteine, Asparagine, and Glutamine What amino acids have aromatic R groups? - Phenylalanine, Tyrosine, and Tryptophan What amino acids have negatively charged R groups? - Aspartate and Glutamate What amino acids have positively charged R groups? - Lysine, Arginine, and Histidine What is isoelectric focusing? - Proteins are electrophoresed in a pH gradient gel. Each protein will move in the gel as long as the protein contains a charge What does SDS do? - It binds to proteins and denatures it. All proteins have same mass/ charge ratio How do you determine the Amino Terminus? - 1. Make a derivative of the N-terminus with a marker molecule 2. Hydrolyze the peptide 3. N-terminal AA is identified by chromatography- modified amino acid will elute differently than unmodified AA What molecule does Edman Degradation use? - Phenyl Isothiocyanate (PTH) What does Edman Degradation do? - It removes one amino acid at a time. The limit is 50 amino acids. After 50 amino acids, the polypeptide must be hydrolyzed into smaller fractions Where does Cyanogen Bromide cleave? - Cleaves only on the caryboxyl side of Methionine residues Where does Trypsin cleave? - Trypsin cleaves on the carboxyl side of positive residues such as Arginine and Lysine What happens in Disulfide Position? - It is a diagonal electrophoresis. The peptides are cleaved without destroying the disulfide bonds and then exposed to performic acid vapors. The performic acid vapors convert any S-X bond to a SO3-. These fragments will be off the diagonal In Peptide Synthesis, what is the protecting group? - Fmoc What is the group that activates amino acid 2? - DCC- Dicyclohexylcarbodiimide What acts as the nucleophile in Peptide Synthesis? - Amino acid 1 that is connected to the polystyrene bead. What causes the polystyrene bead to disconnect from amino acid 1? - HF In what order does peptide synthesis, synthesize amino acids? - Carboxy end to the amine end In what order does the body synthesize amino acids? - Amino terminus to carboxy terminus What are the hydrogen bonds in Alpha Helix? - The carboxyl group is hydrogen bonded with the Hydrogen on the Nitrogen 4 residues away. Alpha helix is clockwise, or right handed