exam Q's

Question 1

explain why enzymes are essential in all living things

Answer 1

-they are biological catalysts
-they lower activation energy
-and catalyse reactions

Question 2

enzymes digest insects that fall into heliamphora traps. is the mode of action of these enzymes extracellular or intracellular?

Answer 2

extracellular
enzymes are released by plant cells into the trap
digestion doesn’t occur inside the cells.

Question 3

The student wished to determine the mass of enzyme in 250 cm3 of an enzyme solution of unknown concentration. To determine the concentration of this enzyme solution, the student first carried out the biuret test on three enzyme solutions of known concentration: * solution 1 * solution 2 * solution 3 0.5mgcm-3 of enzyme 1.0mgcm-3 of enzyme 2.0mgcm-3 of enzyme 0.0 0.60 0.40 0.20 0.00 0.80 After completing the biuret tests, the absorbance of light by each solution was measured using a colorimeter. The student plotted a graph of the results. The graph is shown in Fig. 3.1.

Answer 3

mass= concentration x volume

1.4 x 0.25= 0.35

Question 4

The student then carried out the same procedure on the enzyme solution of unknown concentration. The absorbance reading on the colorimeter was 0.8 arbitrary units. Using the line drawn by the student in Fig. 3.1, determine the concentration of the enzyme solution. Calculate the mass of enzyme, in grams, in 250 cm3 of the enzyme solution. Show your working. Give your answer to two decimal places. [2]

Answer 4

test more (known) , concentrations / solutions ; between 1.0 and 2.0 / near 1.4

Question 5

Outline the practical procedures the student would have taken to generate the point on the graph at the origin (0.0, 0.00). [2]

Answer 5

carry out Biuret test ; (using) no enzyme

Question 6

how would this calculated rate differ from the true initial rate of reaction?

Answer 6

it would be higher

because of higher concentration of substrate at the start.