Multiple Choice Questions

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An electric current is passed through an aqueous solution of a mixture of alanine (isoelectric point 6.0), glutamic acid (3.2) and arginine (10. 7) buffered at pH 6. What is the fate of the three acids?

  • Glutamic acid migrates to anode at pH 6. Arginine is present as a cation and migrates to the cathode. Alanine in a dipolar ion remains uniformly distributed in solution

  • Glutamic acid migrates to cathode and others remain uniformly distributed in solution.

  • All three remain uniformly distributed in solution.

  • All three move to cathode


A.

Glutamic acid migrates to anode at pH 6. Arginine is present as a cation and migrates to the cathode. Alanine in a dipolar ion remains uniformly distributed in solution

Amino acids exists as Zwitter ions which contain both positive and negative charge but are overall electrically neutral. At their isoelectric point, amino acids do not migrate to any electrode and remain uniformly distributed in the solution. Thus, alanine (isoelectric point 6.0) does not move to any electrode.

At a pH lower than their isoelectric point, they exist as cation and move towards cathode. Thus, arginine (isoelectric point 10. 7) exist as cation.

At a pH higher than their isoelectric point, they exist as anion and move towards anode. Thus, glutamic acid (isoelectric point 3.2) at pH 6.0 moves towards anode.


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A certain compound gives negative test with ninhydrin and positive test with Benedict's solution. The compound is

  • a protein

  • a monosaccharide

  • a lipid

  • an amino acid


In aqueous solution glucose remains as 

  • only in open chain form

  • only in pyranose form

  • only in furanose form

  • n all three forms in equilbrium


In DNA, the consecutive deoxynucleotides are connected via

  • phosphodiester linkage

  • phosphomonoester linkage

  • phosphotriester linkage

  • amide linkage


Which of the following is a peptide linkage?

  • -CO-NH

  • -CO-NH2

  • -CO-O-NH4


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Which of the following reagent is used to identify fructose?

  • Neutral FeCl3

  • CHCH3/ KOH (alcohol)

  • Ammonical AgNO3

  • Iodine


Which one is not a constituent of nucleic acid?

  • Uracil

  • Guanidine

  • Phosphoric acid

  • Ribose sugar


Ribose and 2-deoxyribose can be differentiated by

  • Fehling's reagent

  • Tollen's reagent

  • Barfoed's reagent

  • Osazone formation


Glucose when treated with conc. HNO3 gives

  • acetic acid

  • saccharic acid

  • gluconic acid

  • sorbitol


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The number of amino acids and number of peptide bonds in a linear tetrapeptide (made of different amino acids) are respectively.

  • 4 and 4

  • 5 and 5

  • 5 and 4

  • 4 and 3


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