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TLS Online TPP Program

#Question id: 1260

Which of the following statement regarding RTK/Ras pathway is incorrect?

#Unit 4. Cell Communication and Cell Signaling

  1. Receptor activation leads to re-localization of Sos from the cytosol to the membrane, which brings Sos close to its substrate, Ras∙GDP, which is already bound to the plasma membrane by means of a covalently attached lipid.

  2. Binding of Sos to Ras∙GDP leads to conformational changes in the switch I and switch II segments of Ras, thereby opening the binding pocket for GDP so it can diffuse out.

  3. The SH2 domains in GRB2 selectively bind to proline-rich sequences in Sos; different SH3 domains in other proteins bind to proline-rich sequences distinct from those in Sos.

  4. Ras is activated by the exchange of GDP for GTP. Active Ras∙GTP binds to the N-terminal regulatory domain of Raf, a serine/threonine kinase, thereby activating its kinase activity.

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TLS Online TPP Program

#Question id: 33240

#Unit 1. Molecules and their Interaction Relevant to Biology

Metal ions participate in the catalytic process
A. By binding to substrates to orient them properly for reaction.
B. By mediating oxidation–reduction reactions through reversible changes in the metal ion’s oxidation state.
C. By electrostatically stabilizing or shielding negative charges.
Which is/are correct statement
TLS Online TPP Program

#Question id: 33241

#Unit 1. Molecules and their Interaction Relevant to Biology

Carbonic anhydrase contains an essential Zn2+ ion which is involved in
TLS Online TPP Program

#Question id: 33242

#Unit 1. Molecules and their Interaction Relevant to Biology

Reactants must come together with the proper spatial relationship for a reaction to occur in the active site of enzymes called as
TLS Online TPP Program

#Question id: 33243

#Unit 1. Molecules and their Interaction Relevant to Biology

Enzyme’s proximity and orientation effects alone can enhance reaction rates by 
TLS Online TPP Program

#Question id: 33244

#Unit 1. Molecules and their Interaction Relevant to Biology

Charged groups may help stabilize the transition state of the reaction, a phenomenon termed as 
TLS Online TPP Program

#Question id: 33245

#Unit 1. Molecules and their Interaction Relevant to Biology

   

Reaction catalyzed by proline racemase from Clostridium sticklandii is thought to occur via a planar transition state as shown above. The compound can affect reaction significantly as