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TLS Online TPP Program

#Question id: 2858

When lactose enters the cell, it is converted to allolactose. It is allolactose (rather than lactose itself) that controls the Lac repressor. Paradoxically, the conversion of lactose to allolactose is catalyzed by b-galactosidase, itself encoded by one of the lac genes. How is this possible? Which statement is incorrect according lac genes expressions?

#Unit 2. Cellular Organization

  1. The expression of the lac genes is leaky, even when they are repressed, because, allolactose binds to a part of the Lac repressor distinct from its DNA-binding domain.

  2. In the absence of allolactose, the repressor is present in a form that binds its site on DNA (and so keeps the lac genes switched off).

  3. Allolactose has altered the shape of the repressor, the protein can no longer bind DNA, and so the lac genes are no longer repressed.

  4. This leakiness ensures that there is a low level of b-galactosidase in the cell even in the absence of glucose, and so there is enzyme poised to catalyze the conversion of lactose to allolactose.

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TLS Online TPP Program

#Question id: 27631

#Unit 1. Molecules and their Interaction Relevant to Biology

Interactions between amino acid residues at the ends of the helical segment and the electric dipole inherent to the  helix so which of the following representing the actual dipole moment along the peptide bond atoms C=O– N-H
TLS Online TPP Program

#Question id: 27632

#Unit 1. Molecules and their Interaction Relevant to Biology

The two forms of poly(Pro) helix all cis (I) or all trans (II) peptide bonds with different no of amino acid per turn

(a) poly(Pro) I as a right-handed helix with 3.3 residues per turn 

(b) poly(Pro) I as a right-handed helix with 3 residues per turn 

(c) poly(Pro) II is a left-handed helix with 3 residues per turn.

(d) poly(Pro) II is a left-handed helix with 3.3 residues per turn.

Choose the correct options of the following
TLS Online TPP Program

#Question id: 27633

#Unit 1. Molecules and their Interaction Relevant to Biology

Amino acid and condtion/propensity of forming helix is given
(a) Polyleucine and polyalanine readily do not form a-helical structures.
(b) Polyleucine and polyalanine readily form a-helical structures.
(c) Below pH 12, polylysine chain, readily forms an a-helix
(d) At pH 12, polylysine chain, readily forms an a-helix
(e) Below pH 5olyGlu readily do not forms an a-helix.
(f) Below pH 5olyGlu readily forms an a-helix.
Choose the correct options of the following
TLS Online TPP Program

#Question id: 27634

#Unit 1. Molecules and their Interaction Relevant to Biology

Which of the following set of amino acid can form beta sheet
TLS Online TPP Program

#Question id: 27635

#Unit 1. Molecules and their Interaction Relevant to Biology

The arrangement of successive amide planes has a pleated appearance due to the
TLS Online TPP Program

#Question id: 27636

#Unit 1. Molecules and their Interaction Relevant to Biology

Each single strand of the beta-sheet structure can be pictured as a twofold helix, that is, a helix with