Biochemistry Exam #2 (Module 3) questions and answers 100% verified.

Biochemistry Exam #2 (Module 3) questions and answers 100% verified. (Exam question 21) Dialysis - correct ates small molecules from large molecules (Exam question 30) When a protein is 'salted-in', it precipitates and is removed form a solution. - correct answers.False When we purify protein, we are going against the natural tendency toward disorder (we are fighting against entropy). - correct answers.True When centrifuging sub-cellular structures, what organelles pellet out at 10,000 x g? - correct hondria A quick way to start purifying a protein is to first fractionate cellular organelles and collect the one with the protein of interest. If you want to collect fractions that separately contain nuclei, mitochondra, endoplasmic reticulum, and cytosol, how is this most easily done? - correct ifugation (Exam question 11) Dialysis is carried out on a solution containing a 100 kD red protein, a 10 kD yellow protein, and a 2,000 kD blue dye by placing the mixture in the dialysis bag. If the dialysis bag has a pore size of 50 kD, what color will the solution in the bag be after several equilibrations and buffer exchanges? - correct + blue = purple (Exam question 12) To purify an enzyme, liver cells are homogenized in a Dounce tube and centrifuged at 500g for 10 minutes. The supernatant is centrifuged further for 10,000g for 20 minutes, then the resulting supernatant is centrifuged at 100,000g for one hour. The resulting pellet is resuspended in buffer and used for enzyme kinetics. The enzyme being studied must be found in - correct endoplasmic reticulum Gel-filtration chromatography largely separates proteins (or other molecules) based upon - correct In IMAC, proteins of interest form ___________ with the contents of the column immobilizing them until they are eluted. - correct -ligand bonds IMAC chromatography separates molecules based on size. - correct answers.False Immobilized metal affinity chromatography (IMAC) will retain proteins - correct 4-6 consecutive histidine residues Which of the following proteins would elute first from a size exclusion chromatography column? - correct in Z (MW 250,000 g/mol; charge +3) Denatures protein will usually not bind to an affinity column as well as normal, folded protein. - correct answers.True In ion-exchange chromatography, molecules are separated based on - correct answers.Charge (Exam question 5) Ion exchange chromatography - correct ates molecules based on charge (Exam question 4)Which of the following proteins will elute first (go through the fastest) in size exclusion (also called molecular exclusion) chromatography? - correct answers.Protein X (Molecular weight 149,000 g/mol, charge +1) In ion exhcange chromatography using diethylaminoethyl (DEAE) cellulose, which of the following amino acids would elute last? - correct answers.D (Exam question 26) In affinity chromatography, molecules are separated based primarily on their charge. - correct answers.False A protein that is a tetramer with four identical subunits of 10 kD each would show major bands on a properly run SDS-PAGE gel at - correct answers.10 kD (Exam question 17) A sample of blood proteins is separated on a 2D-gel. If the patient is young enough to express significant amounts of both fetal and adult hemoglobin, and fetal hemoglobin has less positive charges than adult hemoglobin but the sizes are nearly identical, where would they be found on the gel relative to one another? - correct answers.At the same position in the SDS-PAGE dimension, but fetal hemoglobin will be found at lower pH in the isolectric focusing dimension Which of the following amino acids has its isoelectric point at the highest pH? - correct ine If a protein has an isoelectric point (pI) of 10.2, which of the following amino acids is it likely to have a lot of? - correct answers.H and R In normal SDS-PAGE, separation is based on - correct (Exam question 18) In SDS-PAGE, proteins separate based primarily on - correct In the 2D gel image below, the red spot represents and unmodified version of a protein with a molecular weight of 150 kD. Which grey spot is appropriately placed to represent a version of that protein that has been phosphorylated at a serine reside (a phosphate group has been covalently attached to the serine hydroxyl group)? The SDS-PAGE portion of the gel spans from 10 kD to 2000 kD. - correct answers.4 Which of the following amino acids has an isoelectric pH of 3.2? - correct mic acid In SDS-PAGE, the SDS serves to - correct proteins constant charge/mass and denature proteins If a protein has an isoelectric point (pI) of 3.2, which of the following amino acids is it likely to have a lot of? - correct answers.D and E Which of the following amino acids has its isoelectric point at the lowest pH? - correct tic acid Cyanogen bromide will cleave the peptide KWNEMDAR - correct the M (Exam question 25) A reagent that oxidizes cystines (cysteine disulfides) into cysteic acids that can no longer form disulfide bonds is - correct rmic acid In the Edman Degradation, phenyl isothiocyanate reacts with ___________________. - correct N-terminal amino acid of a peptide A heptapeptide was found to have an amino acid composition of asp. leu, lys, met,phe and tyr. Trypsin has no effect on the heptapeptide. One cycle of Edman degradation renders the product whose structure is shown below. Chymotrypsin treatment yields a dipeptide and a tetrapeptide, as well as a free amino acid. The tetrapeptide is known to contain asp, leu, lys, and met. Cyanogen bromide treatment generates a dipeptide that is determined to originate from the N-terminus of the heptapetide, a tetrapeptide, and free lys. The peptide sequence in single letter amino code is ___________________. - correct answers.FMYDLMK (Exam question 16) You start a protein purification with 15 g of a crude mixture of mitochondrial protein and measure the enzyme activity and get 150,000 units of activity. You then do several rounds of chromatography, and end up at 150 mg of protein that assays to give 100,000 units of activity. The percent yield of the enzyme you are trying to purify is - correct answers.67% Dithiothreitol (DTT) is used to - correct e disulfide bonds Chymotrypsin - correct es proteins after large hydrophobic amino acid residues (Exam question 13) A reagent that selectively cleaves after methionine residues is - correct answers.Cyanogen bromide