The diagram below represents a hypothetical operon in the bacterium E. coli.  The operon consists of two structural genes (A and B) that code for the enzymes A-ase and B-ase, respectively, and also includes P (promoter) and O (operator) regions as shown.

 When a certain compound (X) is added to the growth medium of E. coli, the separate enzymes A-ase and B-ase are both synthesized at a 50-fold higher rate than in the absence of X (which has a molecular weight of about 200).  Which one of the following statements is true of such an operon?

#Question id: 905

#Unit 1. Molecules and their Interaction Relevant to Biology

Which of the following is correct about chaperones

A) renature and denatured proteins.

B) help cells repair damage due to heat shock.

C) assist protein self assembly.

D) donot use ATP to fold proteins.

#Question id: 906

#Unit 1. Molecules and their Interaction Relevant to Biology

Which of the following is least likely to result in protein denaturation?

#Question id: 907

#Unit 1. Molecules and their Interaction Relevant to Biology

Thermodynamics of protein folding is depicted as a free energy vs folding process:

Choose the correct match for regions mentioned in the figure

#Question id: 908

#Unit 1. Molecules and their Interaction Relevant to Biology

Molecular chaperones are a class of proteins that play a role

#Question id: 909

#Unit 1. Molecules and their Interaction Relevant to Biology

Most proteins denature at both high and low pH. At high pH, the ionization of internal tyrosines is thought to be the main destabilizing influence, whereas at low pH, the protonation of buried histidines. A titration curve for the unfolding of the enzyme ribonuclease is shown in Figure. Given the relation between the titration curves for protein unfolding and histidine protonation, which of the following conclusion can be drawn correctly?

A. The sharp transition in graph indicates a highly cooperative process; when the protein starts to unfold, it completes the process rapidly

B. The sharp transition in graph indicates a highly noncooperative process

C. Several buried histidines can ionize when the chain starts to unfold, so that when one goes, they all go together due to cooperative behaviour of protein folding

D. Buried histidine (pK of 4 in this example) becomes accessible to solvent, its pK will shift toward its normal value of 6, significantly steepening its titration curve.

#Question id: 910

#Unit 1. Molecules and their Interaction Relevant to Biology

Experiments on denaturation and renaturation after the reduction and reoxidation of the —S—S— bonds in the enzyme ribonuclease (RNase) have shown that: