Cheat Sheet - Final Biochem Part II

Capitulo 3 1- The table shows the data for purification of a hypothetical protein. Determine the missing values for the specific activity for the three types of chromatography. 2- The log of the molecular weights of proteins can be plotted against the relative mobility on SDS-PAGE. Using this plot, the relative mobility of an unknown protein can be used to estimate its molecular weight. The molecular weights are in daltons. 3- Predict the charge on the major species of the peptide Ile–Arg–Glu–Ala–Lys–Ser–Gln at pH 7.0  . 4- Classify each amino acid by the chemical properties of its side chain (R group) at pH 7 . Select the amino acid that fits best in each category. Each amino acid will be selected only once. 5- Place each charge form of alanine under the pH condition where it would be the predominant form. The pk   a  values for the carboxyl group and amino group of alanine are approximately 2.3 and 9.7, respectively. 6- Size-exclusion column chromatography and SDS-PAGE are methods used to separate mixtures of proteins. Match each statement with the appropriate category. 7- In the figures are the titration curves of two amino acids. Consider the first titration. 8- Choose the functions of amino acids (free or in a bound form). 9- For each of the amino acids, predict the direction of migration during electrophoresis at the given pH. 10- A generic protein that is 387 amino acid residues long will have a molecular weight 11- One method for separating polypeptides utilizes their different solubilities. The solubility of large polypeptides in water depends upon the relative polarity of their R groups, particularly the number of ionized groups. The more ionized groups there are, the more soluble the polypeptide. 12- Match each structure and description to the appropriate amino acid. 13- If a scientist wanted to separate two similarly sized and charged proteins, which method of column chromatography would be best? 0 14- Name the tripeptide using the three letter amino acid abbreviations separated by a hyphen. (For example: Gly-Ala-Phe). 15- Threonine is a standard amino acid with a polar side chain. 16- Which of the statements about peptide bonds are true? 17- Isoelectric focusing can separate peptides based on their relative contents of acidic and basic residues. When voltage is applied to an electrophoretic gel with a pH   gradient, each peptide migrates until it reaches a point where it has no net charge. The pH   at this point is the isoelectric point (pI)   for that peptide. 18- For each amino acid, the name, three-letter abbreviation, or one-letter abbreviation is given. Complete the missing information. Cont…. 19- A solution contains a mixture of three proteins, catalase, ovalbumin and cytochrome 𝑐. The table gives the molecular weight, diffusion coefficient, and pI for the three proteins. 20- Mixtures of amino acids can be analyzed by separating the mixture into its components through ion-exchange chromatography. Amino acids placed on a cation-exchange resin containing sulfonate (−SO   ) groups flow down the column at different rates because of two −3 factors that influence their movement: ionic attraction between the sulfonate groups on the column and positively charged functional groups on the amino acids, and hydrophobic interactions between amino acid side chains and the strongly hydrophobic backbone of the polystyrene resin. 21- Label the graph with the correct axes for a standard curve used in a spectrophotometry experiment. 22- Refer to the chart of amino acid structures to help answer this question. 23- All amino acids have two ionizable functional groups: an α-amino group (average p  𝐾a of 9.4) and an α-carboxylic acid group (average p  𝐾  a of 2.2). Cysteine has an ionizable side chain (R group) with a p  𝐾  a of about 8.3. One of the possible ionization states of cysteine is shown in the image. 24- Select the true statements about SDS‑PAGE, a method of separating proteins. Assume that SDS‑PAGE is performed under reducing conditions. 25- The structure of the amino acid L-alanine is shown. 26- The figure shows a two-dimensional gel of a mixture of proteins A, B, and C. The vertical axis represents SDS-PAGE separation, run from top to bottom. The horizontal axis represents isoelectric focusing with a pH gradient that runs from left(high pH) to right