2.5 – Enzymes

1.Three flasks were prepared for an analysis of the activity of amylase. At time zero, each of the substances indicated in the diagrams was added. Which flask(s) could provide support for the hypothesis that heat denatures enzymes?

2. The graph shows the effect of increasing the substrate concentration on the rate of an enzyme-catalysed reaction. What is occurring during the phase indicated by section Y of the graph?

3. Cladograms can be created by comparing DNA or protein sequences. The cladogram on the left is based on DNA sequences and the cladogram on the right is based on comparing protein sequences. What is the reason that cladograms based on DNA sequences are more reliable predictors of the phylogenetic relationship of species than cladograms based on protein sequences?

4. In an experiment the effect of changing pH on an enzymatic reaction is tested. Which could be a dependent variable in this kind of experiment?

5. The bacterium Neisseria gonorrhoeae causes infections related to the human reproductive system. The graph shows the percentage of samples in which this bacterium showed resistance to six antibiotics over a period of ten years. What is a possible explanation for the total percentage resistance being larger than 100% in 2010?

6. A fever in a normally healthy adult during an illness is not usually a problem and can be regarded as a defence mechanism. However, a fever higher than 41°C might be dangerous. What is the cause of the possible damage due to a high fever?

7. It is possible to attach β-galactosidase to alginate beads for use in the production of lactose-free milk. What are enzymes that have been attached in this way called?

8. What is decreased when lactase is added to milk?

9. How can the activity of a human amylase enzyme be increased during a laboratory experiment?

10. Why does exposure to high temperatures cause an enzyme to lose its biological properties?

11. Which is the activation energy of a reaction when it is catalysed by an enzyme?

12. In enzyme experiments, the rate of enzyme activity often gradually decreases. What is most likely to cause this decrease?  

13. What contributes to the structure of an enzyme?

14. Which graph shows the effect of increasing substrate concentration on enzyme activity?

15. What is produced when the enzyme lactase is added to milk?  

16. For what purpose is the enzyme lactase useful?  

17. How does an increase in temperature affect enzyme activity?

18. Which graph shows the effect of increasing the substrate concentration on enzyme activity?

19. What is denaturation?

20. The graph below shows the effect of substrate concentration on enzyme activity. What conclusion can be drawn about section X of the graph?

21. Which variable has the least effect on enzyme activity?

22. What happens as an enzyme becomes denatured?

23. Which of the following statements is true about enzymes?