Consider the statements below and indicate if they are true or false. Hydrophobic proteins are concentrated on the outside of the casein micelle [ Select ] Proteins are polymers of amino acids that are connected by peptide bonds [ Select ] When the pH of milk is lowered to the isoelectric point, the casein proteins become less soluble Select ]

Fill in primary, secondary, tertiary or quaternary into the following statements about proteins: Global folding of peptides stabilized by side-chain interactions is known as a ___(A)___ protein.  Multiple tertiary structures bonded together is a called a  ___(B)___ protein. A ___(C)___ protein is a sequence of amino acids bonded together. A protein in the alpha helix formation is called a ___(D)___ protein, and utilizes H-binding interactions on the amino acid backbone to hold the shape.   Select one: a. (A) tertiary, (B) secondary, (C) primary, (D) quaternary b. (A) primary, (B) quaternary, (C) tertiary, (D) secondary c. (A) quaternary, (B) tertiary, (C) primary, (D) secondary d. (A) tertiary, (B) quaternary, (C) primary, (D) secondary

What test(s) could you use to determine whether an unknown solution in a test tube could be an amino acid or a protein? Specifically, what test distinguishes between amino acids and proteins?

What do your findings suggest about the stability of proteins in the presence of organic solvents?

Which interaction(s) is/are involved in the primary structure of a protein (choose all that apply)? a. hydrogen bonding b. salt bridge c. hydrophobic effects d. covalent peptide bond

Proteins 1 and 2 interact strongly. A significant part of the interaction is between the amino acid side chains shown below. Protein 1= arginine C6H14N402 . Protein 2 = glutamic acid C5H9NO4 A mutation occurs in protein 2 that changes the amino acid shown above to one of the amino acids shown below. What change should disrupt the interaction between proteins 1 and 2 the most? the least? Protein 2- aspartic acid C4H7NO4, protein 2= Lysine C6H14N20 Protein 2= serine C3H7NO3 and protein 2= leucine C6H13NO2 aspartic acid would be the most and leucine would be the least aspartic acid would be the most and serine would be the least lysine would be the most and serine would be the least lysine would be the most and aspartic acid would be the least

Question 2. While internal cysteine amino acid sidechains in proteins undergo oxidation to produce disulfide crosslinks that stabilize the protein structure after folding, solvent-exposed cysteine sidechains can remain in their reduced thiol form and serve as reactive nucleophiles (recall for instance Acyl Carrier Proteins involved in fatty acid biosynthesis or various oxidoreductase enzymes). The reactive thiol groups in proteins can be detected using Ellman's test, wherein the protein is reacted with a disulfide Ellman's reagent to form a new mixed disulfide and a 2-nitro-5-thiobenzoate (TNB) byproduct. Upon addition of base, TNB is deprotonated to form a dianion, which absorbs light in the visible region and can be detected using UV-Vis spectroscopy. Ellman's Reagent CO₂H -NO₂ internal disulfide crosslink O₂N- HO₂C SH solvent- exposed thiol UV Absorbance at 412 nm O₂N- -S TNB²- alkaline pH O₂N- SH HO₂C 2-nitro-5-thiobenzoate (TNB) -NO2 mixed disulfide CO₂H a) Provide a detailed…