E. coli cells were spread on an agar plate, producing 1000 colonies.  The colonies are replica plated on two agar plates containing the antibiotic kanamycin and one agar plate without antibiotics.  All of the colonies are able to grow on the agar plate without antibiotic but only 4 colonies are able to grow on each of the agar plates containing kanamycin.  You notice that the four colonies that grew on each of the kanamycin containing plates are in the exact same position.  This demonstrates

#Question id: 639

#Unit 1. Molecules and their Interaction Relevant to Biology

Match the coenzymes in column I enzymes to class of enzymes in column II

#Question id: 640

#Unit 1. Molecules and their Interaction Relevant to Biology

The data in the table above were collected for an enzyme-catalyzed reaction. The Km for this enzyme is approximately

#Question id: 641

#Unit 1. Molecules and their Interaction Relevant to Biology

Which of the following does NOT describe a mechanism that cells use to regulate enzyme activities?

A. Cells control enzyme activity by phosphorylation and dephosphorylation.

B. Cells control enzyme activity by the binding of small molecules.

C. Cells control the rates of diffusion of substrates to enzymes.

D. Cells control the rates of enzyme degradation.

E. Cells control the rates of enzyme synthesis.

F. Cells control the targeting of enzymes to specific organelles. 

#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

#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: 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?