Enzymes

With reference to Fig. 3.1, Fig. 3.2 and Fig. 3.3, describe and explain the similarities between the progress of the two reactions.

Suggest two advantages of using a colorimeter to investigate the progress of reactions such as those shown in Fig. 3.1.

Calculate the Michaelis–Menten constant, $K_m$, for the enzyme VpSP37 using the information in Fig. 3.4.

Show your working.

$K_m$ = ______

The scientists discovered other enzymes that were suitable for the industrial process. These enzymes had higher $K_m$ values than VpSP37.

Explain the advantage of using the enzyme VpSP37 in the industrial process rather than one of these other enzymes with higher $K_m$ values.

Describe the induced-fit hypothesis of enzyme action.

With reference to the data in Fig. 3.2, discuss whether subtilisin A is effective in preventing the attachment of the larvae.

The scientists extended their investigation by applying the polymer with immobilised subtilisin A to the outside of the bottom of small ships.

Two factors that need to be taken into consideration in this type of investigation are the temperature and pH of the sea water.

Outline two other factors that need to be taken into consideration when investigating the suitability of immobilised subtilisin A as an anti-fouling agent for ships.

Before the induced fit hypothesis was proposed in 1958, scientists believed that the lock and key hypothesis explained how lysozyme catalyses the hydrolysis of peptidoglycan to its products.

Draw labelled and annotated diagrams in the space provided to show how the lock and key hypothesis was used to explain the mechanism of action of lysozyme on peptidoglycan.

Lysozyme and penicillin can be described as antibacterial agents.

Compare lysozyme and penicillin to show the similarities and differences between these two antibacterial agents.

When the concentration of trypsin increases from 2.0% to 4.0%, the time taken for the milk to become transparent decreases by 48%.

Calculate the percentage decrease in the time taken for milk to become transparent when the concentration of trypsin increases from 0.25% to 0.5%.

Write your answer to the nearest whole number.

percentage decrease = ______

Explain the results shown in Fig. 5.1.

State a reason for the difference in percentage of maximum activity of immobilised trypsin and trypsin free in solution at 25°C.

Suggest and explain why the percentage of maximum activity of immobilised trypsin at 55°C is higher than the percentage of maximum activity of trypsin free in solution at 55°C.

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

The students took their final sample at 12 minutes.

Predict the results for absorbance if the students had continued to take samples for a further 10 minutes. Explain your answer.

prediction ______

explanation ______

State an advantage of using a colorimeter in determining the progress of the reaction.

The reaction catalysed by starch phosphorylase occurs at the ends of amylose molecules.

Describe the sequence of events that occurs when starch phosphorylase catalyses the addition of a molecule of glucose to the end of an amylose molecule.

Most enzymes are specific to one reaction.

With reference to Fig. 3.1, explain how the structure of an enzyme provides its specificity.

The drug GNF-5 is used in the treatment of some cancers. GNF-5 affects the activity of TKR by binding to the enzyme component of the complex.

Researchers investigated the effect of GNF-5 on the activity of TKR using different concentrations of ATP solution. In an experiment the activity of TKR was measured with no GNF-5 and with GNF-5.

The results are shown in Fig. 3.2.

The researchers concluded that GNF-5 acts as an inhibitor of the enzyme component of TKR and that it is a competitive inhibitor.

Use Fig. 3.2 to provide evidence for these conclusions.

State how the activity of T315L differs from TKR when no GNF-5 was present.

State how the effect of GNF-5 on T315L differs from the effect of GNF-5 on TKR.

The results of the investigation showed that the product collected in the beaker contained reducing sugar and starch.

With reference to Fig. 6.1, describe a method that would allow the student to use the immobilised amylase to collect a product that contains only reducing sugar.

One standardised variable in the investigation is the size of the alginate beads.

Suggest one reason why using larger or smaller alginate beads in the column would affect the results obtained.

Calculate the initial rate of the reaction.

initial rate of reaction = ______

The procedure was repeated to find the effects on the activity of the pepsin using a competitive inhibitor at the same temperature, $20^{\circ}\text{C}$.

Predict the results that will be obtained using the competitive inhibitor.

The procedure was repeated without the competitive inhibitor but at the higher temperature of $30^{\circ}\text{C}$.

Predict the results that will be obtained at $30^{\circ}\text{C}$.

The students extended their investigation by using pepsin from a different species of mammal. The experiments were carried out at $20^{\circ}\text{C}$ and without a competitive inhibitor.

With reference to Fig. 2.1, explain the advantage of calculating the initial rate of reaction in each experiment.

Suggest and explain why measuring the absorbance of the reaction mixture over 100 s is a suitable method for determining the activity of Neutrase®.

With reference to Fig. 3.1:

• describe the effects of copper sulfate solution and potassium sulfate solution on the activity of Neutrase®
• suggest explanations for the effects that you have described.

Neutrase® can be immobilised in alginate. Immobilised Neutrase® is used in the food industry to produce foods with high nutritional content.

Explain the advantages of using immobilised enzymes, such as Neutrase®, compared with using the same enzymes free in solution.

Suggest how the progress of the reaction could be measured.

In the second experiment, the student cut each of the three remaining pieces of potato to obtain six pieces, each measuring $10\ \text{mm} \times 10\ \text{mm} \times 10\ \text{mm}$.

Using exactly the same conditions, the student measured the progress of the reaction and obtained different results to the first experiment.

Explain why the results of the second experiment were different from the results of the first experiment.

The student then investigated the effect of temperature on the activity of catalase.

On Fig. 6.3, sketch a curve to show how temperature affects the activity of an enzyme such as catalase.