Reference no: EM13893549

1. The inner membranes of cyanobacteria are very similar to those of the thylakoid membrane of chloroplasts. This similarity supports the hypothesis that chloroplasts evolved from symbiotic cyanobacteria. Which other organelles may have originated in the same way? Explain, providing evidence for your choice.

2. Proviruses can be converted from the lysogenic to the lytic pathway under certain circumstances.

a. What circumstances can lead to this shift?

b. Can a virus in the lytic pathway become a provirus? Explain.

3. Some people are born with or develop a condition known as lactose intolerance that causes them to suffer intestinal discomfort when they eat lactose-containing dairy products. This occurs because the lactose that can normally be metabolized and the cleavage products that can then be passed through the intestinal lining cannot be metabolized in these individuals. Can you suggest an explanation for this?

4. Which of the following tripeptides (only one) would be most likely to be soluble in an organic (hydrophobic) solvent like benzene. Explain.
- N - phenylalanine - alanine - glycine - C
- N - leucine - alanine - lysine - C
- N - proline - phenylalanine - alanine - C
- N - arginine - lysine - proline - C
- N - glutamine - asparagine - glycine - C

5. What level of structure in DNA would be disrupted by a reagent that breaks apart hydrogen bonds? Explain.

6. Which of the four classes of amino acids has the following characteristics:

a. Side chains with the greatest hydrogen-bond-forming potential

b. The greatest potential to form ionic bonds

c. Hydrophobic interactions

7. DNA is isolated from two species. Both DNA samples are found to be of the same size (i.e. equal quantities). The samples have G+C/A+T ratios of 2.0 and 2.5.

a. Which DNA sample has a higher G+C content? Explain.

b. Which sample contains the smaller number of H bonds between strands? Explain.

8. What electron or light microscopy technique would you use to observe the following?

a. The fine detail of the outer surface of hair cells in the inner ear.

b. The interior and exterior of surfaces of the plasma membrane to support the fluid-mosaic model of membrane structure. (Hint: it is a procedure used in conjunction with Transmission Electron Microscopy.)

c. Structures in living cells.

9. Why is resolution in electron microscopes so much better than that in light microscopes? (Hint: think about wavelength size)

10. What technique would be used to determine the arrangement of atoms within a protein? (This technique has also been used to detect and locate the spatial arrangement of the atoms of DNA.)

11. Enzymes greatly decrease the activation energy. Explain two of the ways they do this and be specific in terms of chemical mechanisms.

12. You are observing an enzyme-driven reaction. To the reaction mixture, you add a chemical, X, that inhibits the reaction. You suspect that X is a competitive inhibitor. What two pieces of evidence might lead you to this conclusion?

13. You have isolated a new enzyme and have determined the velocity of reaction at three substrate concentrations. You find that the slope of the product-versus-time curve is the same for all three concentrations. What can you conclude about the conditions in the reaction mixture?

14. The ΔG of the following reaction is -2.8 kcal/mol.acetyl phosphate + ADP ?? acetate + ATP
Is the free energy difference per molecule of acetyl phosphate, relative to that of acetate, greater than, lesser than, or equal to that of ATP relative to its dephosphorylated counterpart?

15.a. What is the source of pyruvic acid in the cell? Explain briefly.

b. What is the importance of ADP levels within the mitochondrion, particularly with respect to respiratory rate?

16. Determine which of the substances ubiquinone, NAD+, NADH, O2, and H2O is:

a. the strongest reducing agent ___________________

b. the strongest oxidizing agent ___________________

c. an electron carrier ___________________

17. Refer to Figure 6.7 on page 220 in the textbook. The absorption spectrum indicates the relative light absorption of various pigments in the chloroplast. Which colours of the spectrum are absorbed most strongly by

(a) the chlorophylls and

(b) β-carotene?

18. a. What do plants do to prevent water loss in a hot, dry climate?

b. How would this cause photorespiration in a C3 plant?

c. Why are C4 plants protected? i.e. why are C4 plants immune to photorespiration?

Experiment 1: Effect of Temperature on Amylase Activity

The data for this activity are in Table 1.

Table 1. V of the enzyme amylase at different temperatures, [S] and pH

Environ-mental Conditions: pH = 7
[S] = 90 mM pH = 7
[S] = 60 mM pH = 7
[S]=120 mM pH = 5
[S] = 90 mM pH = 9
[S] = 90 mM

19. Develop a hypothesis to predict the effect of an increase in temperature on amylase activity. Test your hypothesis using the data provided in Table 1. State your hypothesis.

20. Using the data in Table 1.

a. What is the optimal temperature for amylase activity? __________

b. Would amylase isolated from any two organisms (for example, fish amylase vs. amylase from the small intestine of humans) show the same temperature optimum? Explain your answer.

21. Explain why a temperature lower or higher than the optimum would cause decreases in amylase activity. (What is happening to the enzyme to produce these decreases in activity?)

22. If you were to carry out these temperature experiments at a higher or lower [S], what effect would [S] have on the temperature optimum for amylase? Formulate a hypothesis. Using the data from Table 1, test your hypothesis. Explain your results. (Note: Do not submit your plotted graph.)

23. If you were to carry out these temperature experiments at a higher or lower pH value, what effect would this have on the temperature optimum for amylase? Formulate a hypothesis and then, using the data in Table 1, test your hypothesis. Explain your results. (Note: Do not submit your plotted graph.)

Experiment 2: Effect of Substrate Concentration on Amylase Activity

The data for this experiment are in Table 2.

Table 2. V (mM/min) at different [S] (mM) of the enzyme amylase at 37ºC and pH = 7.0

24. Using the data in Table 2, examine the relationship between [S] and amylase activity. To answer the questions, plot the data: V vs [S] and 1/V vs 1/[S] (Lineweaver-Burk). (Note: Do not submit your plotted graphs.)

a. Explain the relationship and your results. What are the Vmax and KM for amylase for this experiment?

25. Compare the values for Vmax and KM derived from each of the two plots (V vs [S] and Lineweaver-Burke).

a. Were these values similar or different? How?

b. If the values were different, explain possible reasons for these differences.

c. Which plot did you find easier to use for determining these values?

26. What do you think would happen if you carried out an experiment with concentrations of starch greater than 400 mM?

27. Briefly compare the effects of a competitive versus a non-competitive inhibitor on an amylase-catalyzed reaction i.e. how would these inhibitors respectively affect KM and Vmax?