#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
#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: 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: 639
#Unit 1. Molecules and their Interaction Relevant to Biology
Match the coenzymes in column I enzymes to class of enzymes in column II
| Enzyme | Reaction Type |
| A. Phosphofructokinase | 1. Redox reaction |
| B. Enolase | 2. Phosphoryl shift |
| C. Phosphoglycerate mutase | 3. Dehydration |
| D. Glyceraldehyde 3 Phosphate dehydrogenase | 4. Phosphoryl transfer |
#Question id: 638
#Unit 1. Molecules and their Interaction Relevant to Biology
Match the following class of enzymes with them
| Enzyme | Class of enzyme |
| A. Hexokinase | 1 |
| B. Phosphoglucoisomerase | 2 |
| C. Glyceraldehyde 3-phosphate dehydrogenase | 3 |
| D. Phosphoglycerate mutase | 4 |
| E. Enolase | 5 |
| F. Aldolase |