A chemiosmotic model  has been proposed  to explain Polar transport , following steps are involve in the transport of auxin polarly;

a) IAA enters the cell either passively in the undissociated form (IAAH) or by secondary active cotransport in the anionic form (IAA–)

b) The cell wall is maintained at an acidic pH by the activity of the plasma membrane H+- ATPase

c) In the cytosol, which has acidic pH, the IAAH form predominates

d) The anions exit the cell via auxin anion efflux carriers that are concentrated at the basal ends of each cell in the longitudinal pathway

Which of the following is the correct statements about the polarly transporting of auxin?

#Question id: 647

#Unit 1. Molecules and their Interaction Relevant to Biology

For the hypothetical reversible reaction where S is converted to P, the rate constant for the forward reaction is 10⁵ s^-1 while that of the backward reaction is 10¹ s_-1. If the reaction is catalyzed by an enzyme, the rate constant for the forward reaction increases 100-fold. What will be the equilibrium constant of the enzyme catalyzed reaction?

#Question id: 646

#Unit 1. Molecules and their Interaction Relevant to Biology

Many biosynthetic pathways are regulated by feedback inhibition of enzymes. In a particular type of feedback inhibition, two endproducts individually do not inhibit an enzyme upstream in the pathway at all, but when both are present they inhibit the same enzyme significantly. What type of feedback inhibition do these inhibitors represent?

#Question id: 645

#Unit 1. Molecules and their Interaction Relevant to Biology

Which of the following is the correct combination of marker enzymes used to identify different organelles during subcellular fractionation of eukaryotic tissue?

#Question id: 644

#Unit 1. Molecules and their Interaction Relevant to Biology

Enzyme X and Enzyme Y are both involved in monosaccharide metabolism. Enzyme X uses glucose as a substrate while Enzyme Y uses fructose as a substrate. At pH=7.0, Enzyme X has a Vmax of 10 μM/s while Enzyme Y has a Vmax of 20 μM/s. Both enzymes have a Km of 3.0 mM for their respective substrates. Which aspects of its reaction will be changed by Enzyme Y?

#Question id: 643

#Unit 1. Molecules and their Interaction Relevant to Biology

The hydrolysis of lactose is catalysed by b-galactosidase as given below

Which of the following could be correct mechanism for this hydrolysis reaction?

A. Nucleophilic attack by the carboxylate group of Glu/Asp on the C-1 carbon atom of the galactose moiety within glucose, releasing glucose and forming an intermediate with the galactose linked to the enzyme through an ester linkage. Water then attacks this carbon atom, displacing the glutamate carboxylate and releasing galactose.

B. Electrophilic attack by the carboxylate group of Glu/Asp on the C-1 carbon atom of the galactose moiety within glucose, releasing glucose and forming an intermediate with the galactose linked to the enzyme through an ester linkage. Water then attacks this carbon atom, displacing the glutamate carboxylate and releasing galactose.

C. Nucleophilic attack by the carboxylate group of Lys/Arg/His or bivalent cation on the C-1 carbon atom of the galactose moiety within glucose, releasing glucose and forming an intermediate with the galactose linked to the enzyme through an ester linkage. Water then attacks this carbon atom, displacing the glutamate carboxylate and releasing galactose.

#Question id: 642

#Unit 1. Molecules and their Interaction Relevant to Biology

The graphs P, Q and R show the variation of rate constant (k) with temperature. The reactions represented by P, Q and R, respectively, are