Practice Questions

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#Question id: 887

Polypeptides fold rapidly by a stepwise process, how does the polypeptide chain arrive at its native conformation?

#Unit 1. Molecules and their Interaction Relevant to Biology

proteins appear to fold in a hierarchical manner, with small local elements of structure forming and then to yield larger elements, which coalesce with other such elements to form yet larger elements and converted into its native conformation
A protein-folding pathway has been highly successful in predicting the three-dimensional structure of small proteins from their amino acid sequence atleast 156 amino acid residue that have acquired their final structure
Vander waal interaction play a significant role throughout the process, as the aggregation of nonpolar amino acid side chains provides an entropic stabilization to intermediates and, eventually, to the final folded structure
The native conformation of the protein folding by stepwise manner such as unfolded→transition state→molten globule→folded conformation by decreasing the free energy

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TLS Online TPP Program

#Question id: 12409

#Unit 6. System Physiology – Plant

The Chemical Structure of ABA Determines Its Physiological Activity, 15 carbon compound

a) The orientation of the carboxyl group at carbon 2 determines the cis and trans isomers of ABA. Nearly all the naturally occurring ABA is in the cis form

b) S enantiomer is the natural form; commercially available synthetic ABA is a mixture of approximately equal amounts of the S and R forms.

c) The S enantiomer is the only one that is active in fast responses to ABA, such as stomatal closure

d) In long-term responses, such as seed maturation, only R-enantiomers are active

e) In contrast to the cis and trans isomers, the S and R forms cannot be interconverted in the plant tissue

Which of the following is the correct prediction about the active form of ABA?

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#Question id: 12407

#Unit 6. System Physiology – Plant

ABA is synthesized via _____A________, the biosynthetic processes occur in_____B_____and ____C_____.

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#Question id: 12404

#Unit 6. System Physiology – Plant

Covalent conjugation of amino acids to IAA can result in___

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#Question id: 12401

#Unit 6. System Physiology – Plant

IAA enters the cell either passively in the undissociated form (IAAH) or by transporter in the anionic form (IAA-) , which one of the following transporter are involved in influx of the anionic form of auxin?

TLS Online TPP Program

#Question id: 12400

#Unit 6. System Physiology – Plant

Given some statements about auxin signal transduction pathway;

a) ARFs bind the AuxRE stably, must form dimers promote transcription by binding to two AuxREs arranged in a palindrome

b) inactive heterodimers may act to inhibit ARF–AuxRE binding, thereby blocking either gene activation or repression

c) Protein encodes the AUX/IAA gene family can inhibit the transcription of early auxin response genes by forming inactive heterodimers with ARFs

d) Auxin induces the transcription of the early response genes by promoting the proteolytic degradation of the inhibitory AUX/IAA proteins so that active ARF dimers can form

e) AUX/IAA turnover to involve ubiquitination by a ubiquitin ligase and proteolysis by the massive 26S proteasome complex

f) A negative feedback loop is introduced into the pathway by virtue of the fact that one of the gene families turned on by auxin is AUX/IAA, which inhibits the response.

Find out the correct sequence from the following above statements;

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#Question id: 12395

#Unit 6. System Physiology – Plant

In theory, auxin could increase the rate of proton extrusion by two possible mechanisms:

I) H+-ATPase activation

II) H+-ATPase synthesis

a) Auxin involves in the activation of ATP-driven proton-pump (H+-ATPase) indirectly

b) ABPs appear to be able to activate the plasma membrane H+-ATPase in the presence of auxin

c) Activity of the H+- ATPase is repressed by the C-terminal domain of the enzyme, which can block the catalytic site in absence of auxin

d) The protein is synthesized on the rough endoplasmic reticulum and targeted via the secretory pathway to the plasma membrane

Find out the correct explanation of given mechanisms.