Part 1: Multiple Choice questions ( 1 point each) 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? a) b) c) d) Flasks I and II after 15 minutes Flasks II and III after 15 minutes Flasks I and III after 15 minutes Flask III at time zero and again after 15 minutes 2. 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? a) b) c) d) Changing substrate concentration Rate of formation of product Variation in temperature Change in pH 3. The graph shows the effect of increasing the substrate concentration on the rate of an enzymecatalyzed reaction. What is occurring during the phase indicated by section Y of the graph? a. b. c. d. The active site of the enzyme is saturated. The enzyme becomes denatured. The substrate concentration has risen too high. The optimum rate is reached 4. 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? a. Inhibited b. Immobilized c. Catalysed d. Activated 5. 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? a. Loss of body mass b. Muscle damage due to shivering c. Overactive metabolic enzymes or denaturing of enzymes d. Spread of infection 6. Why does exposure to high temperatures cause an enzyme to lose its biological properties? a) The substrate blocks the active site at high temperatures. b) Structure of the enzyme becomes changed. c) Chemical reactions cannot take place at high temperatures. d) High temperatures increase the activation energy of reactions. 7. How can the activity of a human amylase enzyme be increased during a laboratory experiment? a) Adding sugar to the mixture b) Decreasing the pH from 7 to 3 c) Increasing the temperature from 20 °C to 37 °C d) Adding water to the mixture 8. Which graph shows the effect of increasing substrate concentration on enzyme activity? 9. For what purpose is the enzyme lactase useful? a. b. c. d. Production of lactose-free milk so that more people can consume dairy products As a dietary supplement to aid in protein digestion of milk For use in coagulating milk protein to make cheese To improve protein consumption in developing countries that lack milk 10. In enzyme experiments, the rate of enzyme activity often gradually decreases. What is most likely to cause this decrease? a. The temperature decreasing b. The enzyme concentration decreasing c. The pH decreasing d. The substrate concentration decreasing 11. What is denaturation? a) b) c) d) A structural change of a protein that results in the loss of its biological properties A change in the genetic code of an organism A change in the amino acid sequence of a protein causing a disruption of its 3D shape The process by which amino acids are broken down and ammonia is released 12. Which variable has the least effect on enzyme activity? a. Temperature b. Light intensity c. pH d. Substrate concentration 13. How does an increase in temperature affect enzyme activity? 14. Which of the following statements is true about enzymes? a. They are used up in the reactions they catalyse. b. Allosteric inhibitors bind to the active site. c. They lower the energy of activation for a reaction. d. They supply the energy of activation for a reaction. 15. What happens as an enzyme becomes denatured? a. The enzyme works faster. b. The enzyme works slower. c. The enzyme can perform a new role. d. The enzyme can make the reverse reaction proceed faster. 16. For which discovery about DNA do Watson and Crick receive credit? a. DNA is the molecule that genes are made of. b. The amount of adenine equals the amount of thymine in an organism. c. Phosphate–pentose bonding along the nucleotide backbone is covalent. d. The shape of DNA is a double helix. 17. What is a similarity between DNA and RNA? a. Both are polymers of nucleotides. b. Both are composed of antiparallel strands. c. Both contain adenine, cytosine and thymine. d. Both contain ribose sugar. 18. What usually distinguishes DNA from RNA? 19. Which sequence shows increasing relative size? 20. The image shows a DNA nucleotide. 21. What is the type of bond between nucleotides? a. Phosphate ester b. Hydrogen c. Phosphodiester d. Peptidiesterase 22. The base sequence of a fragment of DNA is: ACC GTG CAG GAT What is the base sequence on the other strand? a. b. c. d. TGG CAC GTC CTA TGG CUC GTC CTU UGG CTC GUC CUT UGG CAC GUC CUA 23. What is correct for the DNA double helix? 24. What links the pairs of complementary bases in a DNA double helix? a. Covalent bonds b. Hydrogen bonds c. Ionic bonds d. Peptide bonds 25. The percentage of thymine in the DNA of an organism is approximately 30 %. What is the percentage of guanine? a) A. 70 % b) B. 30 % c) C. 40 % d) D. 20 % 26. What type of bond is labelled X? a. Ionic b. Peptide c. Covalent d. Hydrogen 27. The following diagram shows a short stretch of DNA. What bases are indicated by labels Y and Z? 28. Which molecules form the nucleotide marked in the diagram? a. b. c. d. phosphate, deoxyribose and nitrogenous base phosphorus, ribose and nitrogenous base phosphorus, deoxyribose and guanosine phosphate, ribose and guanine 29. What does the structure labelled Y represent? a. Ribose b. Thymine c. Guanine d. Deoxyribose 30. Which points to the 3′ end of a strand of DNA? a. b. c. d. I II III IV Part 2. (Points are shown for each question) 1. Draw graphs of 3 factors that affect enzyme reaction rate. (Do not forget to write axes) (3 points) 2. State two conditions that must be met in order the reaction to happen. (2 points) i) ii) 3. The minimum amount of energy needed for a reaction to start is called _______________________________________. (1 point) 4. Write three properties of enzymes: (eg: they are made up of, how they work, at what conditions they work….) (3 points) i) ii) iii) 5. I want to perform a chemical reaction with iron nails and water to make them rusty. Give three ways to make the reaction faster. (3 points) i) ii) iii) 6. Explain enzyme-substrate specificity. (2 points) 7. What happens to enzymes when human body temperature rises above critical point? (2 points) 8. Explain saturation point with drawing graph. Why enzyme rate cannot be increased after that? (2 points) 9. Define active site with drawing. (2 points) 10. Outline possible effects of acids on enzyme activity. (2 points) 11. Explain the production of lactose-free milk. (5 points) 12. Draw a labelled diagram of a section of DNA showing four nucleotides. (12 points) 13. Give 3 examples to organic and inorganic compounds. ( 6 points) Organic compounds Inorganic compounds 14. Write corresponding numbers of carbon items in the figure below: (1 points) 15. Monomers of nucleic acids are called ____________. (1 point) 16. Label the parts on nucleotide in the figure below. (3 points) 17. What is complementary base pairing? (1 points) 18. Phosphodiester formed by binding of _________________ to ______________. (2 points) 19. Erwin Chargaff discovered that: (4 points) Amount of _______ is equal to amount of ________, and Amount of _______ is equal to amount of ________. 20. Or we can say (referring to question 19): (4 points) ______ + ________ = ________+_________. 21. Write the complimentary DNA strand for the following: (1 point) AATTGCGCTACAT 22. DNA strands are called antiparallel because __________________________________________ ______________________________________________________________________________. (1 points) 23. Function of DNA and RNA is _______________________________. ( 1 points) 24. 3 parts of DNA are: ( 3 points) 25. 3 parts of RNA are: ( 3 points) 26. RNA has nitrogenous base _______ instead of __________ that is found in DNA. (2 points) 27. Fill the table below. (6 points) Difference Bases Pentose sugar Number of strands DNA RNA 28. Write names of two scientists who discovered the DNA structure and won Nobel Prize for biology. (2 points) Part 3: Essay writing. (15 points) Choose one of the options below and write an essay about the topic. a) How scientists discovered the structure of DNA without conducting any experiment. Indicate the advantaged of their method. b) How the smallest change in sequence of bases in DNA may affect the organism? Deduce the results.