TLS Online TPP Program

#Question id: 880


The classic work of Christian Anfinsen in the 1950s on the enzyme ribonuclease revealed the relation between the amino acid sequence of a protein and its conformation. Ribonuclease is a single polypeptide chain consisting of 124 amino acid residues cross-linked by four disulfide bonds. Anfinsen’s plan was to destroy the three-dimensional structure of the enzyme and to then determine what conditions were required to restore the structure.

The critical observation of Anfinsen that the denatured ribonuclease, freed of urea and b -mercaptoethanol by dialysis;

I. The sulfhydryl groups of the denatured enzyme became reduced by air, and the enzyme spontaneously refolded into a catalytically active form.

II. These experiments showed that the information needed to specify the catalytically active structure of ribonuclease is contained in its amino acid sequence.

III. The 105 wrong pairings have been picturesquely termed “scrambled” ribonuclease.

IV. He found that scrambled ribonuclease spontaneously converted into fully active, native ribonuclease when trace amounts of b -mercaptoethanol were added to an aqueous solution of the protein.

Choose incorrect options;

#Unit 1. Molecules and their Interaction Relevant to Biology
  1. I & III

  2. I,II & III

  3. Only III

  4. III & IV

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TLS Online TPP Program

#Question id: 2574

#Unit 2. Cellular Organization

Through a microscope, you can see a cell plate beginning to develop across the middle of a cell and nuclei forming on either side of the cell plate. This cell is most likely ________.

TLS Online TPP Program

#Question id: 2575

#Unit 2. Cellular Organization

NMR studies of the pectin molecules indicate that, which one is not true for pectin ?

TLS Online TPP Program

#Question id: 2576

#Unit 2. Cellular Organization

What effect will addition of AMP-PNP have on axonal transport?

TLS Online TPP Program

#Question id: 2577

#Unit 2. Cellular Organization

Which of the following occur(s) during prophase?

a. Kinetochores capture microtubule (+) ends.

b. Chromosomes move poleward.

c. Chromosomes align on the spindle equator.

d. Centrosomes separate and the spindle begins to form.

e. Chromosome condensation begins.

TLS Online TPP Program

#Question id: 2578

#Unit 2. Cellular Organization

Following statements are regarding to proteins which involve actin filament assembly.

A. To nucleate the assembly of branched actin, Arp2/3 needs to be activated by interacting with a nucleation promoting factor (NPF), in addition to associating with the side of a pre-existing actin filament.

B. The NPF WASp is inactive due to an intramolecular interaction that masks the WCA domain.

C. Two NPFs each bind an actin subunit at their WH2 domains, and together, they activate the Arp2/3 complex through its interaction with their connector and acidic domains.

D. The NPF WASp is activated by a coincidence detection mechanism by which intramolecular interaction in WASp is relieved, allowing the W domain to bind actin and the acidic A domain to activate the Arp2/3 complex.

Which of the following statements represents regulation of the Arp2/3 complex by NPF?

TLS Online TPP Program

#Question id: 2579

#Unit 2. Cellular Organization

Match the following proteins (Column I) with their functions (Column II) during cell organization and movement.

Column I

Column II

A. Profilin

i. Actin nucleating protein

B. Formin

ii. ADP-actin binding protein

C. WASp

iii. Capping protein

D. Gelsolin

iv. Nucleation promoting factor

Which of the following is correct?