At pH 12.48, arginine (pK's 1.82, 8.99, 12.48) would be charged as follows: O 1) -1 alpha-carboxyl, 0 alpha-amino, +0.5 guanidino, -0.5 net charge O 2) 0 alpha-carboxyl, 0 alpha-amino, +1 guanidino, +1 net charge 3) +1 alpha-carboxyl, -1 alpha-amino, -1 guanidino, -1 net charge 4) +1 alpha-carboxyl, 0 alpha-amino, -1 guanidino, 0 net charge

What is the principal form of arginine at pH 8.0? Approximately what fraction is in this form?

Which of the twenty naturally occurring amino acid side chains are charged at a pan of 1.00? pH of 7.00? pH of 12.00? Make a table.

Titration of alanine by a strong base, for example NaOH, reveals two pk's. Which is the titration reaction occurring at pK1 (pK1 = %3D 2.34)? O-NH2 + COH →-NH + H2O O-COOH + OH →-CO + H20 -COOH + -NH2 → -COO" + -NH2+ -CoO +-NH2* → -COOH +-NH2 O -NH3* + OH →-NH2 + H2O

A) Refer to the figure below, Identify and explain the two types of reactions, and describe what are the importance of these reactions to our bodies. Reaction 1 H Monomer Reaction 2 H H OH + H H H₂O H H₂O OH + H H OH OH + H H₂O H₂O OH OH + H OH OH OH OH B) What are the main chemical interactions that determine and maintain the quaternary structure of proteins. Also, what are the conditions that can alter these interactions? [

This amino acid is: (Note that the non-ionized form is shown; remember that backbone groups are irrelevant to classification) a) Polarized (+) charged b) Nonpolar c) Polar and (-) charged d) Polar uncharged

Φ and ψ in the Ramachandran plot (below) are: a) Rotational angles around the bond between the α-carbon and N-H (Φ) and C=O (ψ). b) Amino acid solubility in octanol (Φ) and water (ψ). c) Hydrogen bond angles in α-helices (Φ) and β-sheets (ψ). d) Amino acid solubility in water (Φ) and octanol (ψ).

The carbon-nitrogen peptide bond is rigid, but rotation can take place about the N-Ca and the Ca-C bonds in a protein (Ca is the a carbon atom). These bond angles define the conformation of the peptide chain. Consider the Ramachandran plot to answer both questions. Which dihedral angles and residues would not likely occur in a ß sheet? 180 120 60 -60 -120 -180 -180 180 + (degrees) OA. 0=-51°; U=+153°; many Gly and Pro residues D=+60°; u=+60°; many Gly residues В. OC. D=-57°; W=-49°; many Ala residues D=-139°; W=+135°; many Val residues OD. D=-120°; U=+120°; many Tyr residues DE. (səəbap)

The pka of the side chain of histidine is 6.00. What is the percent of protonated histidine at pH 6.4? 15.3% 28.5% 45.3% O 66.6%

Compare the stability of the two salt bridges shown circled in blue at pH 8.4. The carboxylate ions are completely de- protonated at pH 8.4 The pka of the amino group (upper left) is 8.1 and the pka of the amino group (bottom right) is 8.7. (d) NH, F-8- Ed (b) O-H- M5 CH₂COOH (c) 5 (b) CH, CH. H--O=C (d) -H H CH,OH (b) KCHJ NH, (a) The bottom right salt bridge is stronger due to the partial positive charge of +2/3. The bottom right salt bridge is stronger due to the partial positive charge of +1/3. The upper left salt bridge is stronger due to the partial positive charge of +1/3. The upper left salt bridge is stronger due to the partial positive charge of +2/3.