Many of the carriers of Sucrose–H+ symporters in the phloem play various role in transport, most of the transporters are found in source, path, and sink tissues. Some carriers are characterized such as;

a) SUT1, has high-affinity / low-capacity transporter found in the minor veins of source tissues, appears to be important in phloem loading.

b) Important role of SUT1 in phloem loading appears to be complemented by SUT4, which is low-affinity/high-capacity carrier

c) SUT2, appears to function as a sucrose sensor. This is indicated by findings showing that SUT2 is more highly expressed in sink and path tissues than in source leaves.

d) The major sucrose transporters in phloem loading into the companion cells and final uptake into companion cells appears to be the function of SUT4

Which of the following combination is correct?

#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: 638

#Unit 1. Molecules and their Interaction Relevant to Biology

Match the following class of enzymes with them

#Question id: 637

#Unit 1. Molecules and their Interaction Relevant to Biology

Effect of temperature on enzymatic catalysis is analysed by the rate v of a chemical reaction varies with temperature according to the Arrhenius Equation which explains the sensitivity of enzyme reactions to temperature. A plot to determination of the activation energy Ea involves

#Question id: 636

#Unit 1. Molecules and their Interaction Relevant to Biology

DNA polymerase contains a lysine residue that is important for binding to DNA. Mutations were found that converted this lysine to either glutamate, glycine, valine, or arginine. Which mutations would be predicted to be the most and least harmful to the ability of the enzyme to bind DNA?

#Question id: 635

#Unit 1. Molecules and their Interaction Relevant to Biology

The enymatic rate constant (kcat/Km) of orotidine 5ʹ-phosphate decarboxylase is 6 x 10⁷ M^-1s^-1 and the nonenzymatic rate constant (kn) is 3 x 10^-16 s^-1.  What is the value of the enzymeʹs catalytic proficiency?

#Question id: 634

#Unit 1. Molecules and their Interaction Relevant to Biology

An enzyme has a Vmax of 50 micromol product formed (minute x mg protein)-1 and a Km of 10 microM for the substrate. When a reaction mixture contains the enzyme and 5 microM substrate, which of the following percentages of the maximum velocity will be closest to the initial reaction rate?