CAIE A-Level Biology AS 2.1 Testing for Biological Molecules Questions

Many flowers produce a sweet solution called nectar. Bees provided with nectar use enzyme Q to change the nectar into honey.

After testing a sample of nectar for the presence of reducing sugar using standard laboratory reagents, the sample was blue. After testing a sample of honey in the same way, the sample was orange.

Which conclusion about the reaction catalysed by enzyme Q is consistent with these results?

Glucose is used in the synthesis of amylose. Glucose is first converted to glucose 1-phosphate (G 1-P).

Starch phosphorylase is an intracellular enzyme that can catalyse the synthesis of amylose from G 1-P, which is the substrate for the reaction:

n= a large number
Students used a colorimeter to investigate the progress of the reaction.
The students made a reaction mixture containing $0.01 \mathrm{~mol} \mathrm{dm}^{-3} \mathrm{G}$ 1-P in a buffer solution at pH6.0. A very small quantity of amylose was added to initiate the reaction.

A solution of starch phosphorylase was added to the reaction mixture and samples were taken at 1-minute intervals. Each sample was added to a dilute iodine solution, stirred and then poured into a cuvette. The absorbance of each solution was recorded.

The results of the investigation are shown in Fig. 2.1.

Explain why the absorbance increases, as shown in Fig. 2.1.

Which set of steps is the best method for conducting the emulsion test for lipids?