CHAPTER 2 REVIEW SHEET
1. What percent of living things depend on water?
2. Water accounts for between 60% and 90% of a cell’s __________. Identify two
exceptions. How is water still important to them?
3. What four macromolecules assume their characteristic shape because of water?
4. Much of the _______________ machinery of cells operates in an _______________
environment because water is an essential _______________ and a _______________
for many cellular reactions.
5. Draw a 3D Lewis structure for water, and apply its net dipole. This makes water
_______________.
6. Label the parts of the given diagram.
H
H
O
O
_______________ __________ (Hf° = –460 kJ/mol)
H
H
_______________ __________ (Hf° = –20 kJ/mol)
7. When water is heated, which of the above breaks first?
8. H-bonding is a type of _______________ force; specifically, a ______________________________ force.
9. Provide an example as to the importance of H-bonding in biochemistry.
10. How does water’s specific heat compare to other liquids? _______________ Therefore,
a rather __________ amount of heat is required to change the temperature of water.
Therefore, since 60%-90% of a cell’s mass is water, this allows temperature fluctuations
to be _______________. This is a critical biological feature due to the fact that reaction
__________ is sensitive to temperature changes.
11. How does water’s heat of vaporization compare to other liquids? Why is this biologically
important?
12. The _______________ polar groups on a molecule, the more soluble it will be.
13. The _______________ the hydrocarbon chain on a molecule, the less soluble it will be.
14. Decide whether or not these molecules will dissolve in water.
a.
OH
b.
NH2
15. Briefly cite three reasons why the behavior of solutes in cytoplasm is different than how
they behave in water.
16. _______________ is the process by which a solvent will pass from a lower-concentrated
solution to a higher-concentrated solution.
17. What prevents the flow of solvent when a solvent-permeable membrane separates
compartments that have drastically different concentrations of dissolved particles?
18. What can cells do to avoid bursting due to osmosis?
19. What two critical processes result from the hydrophobic effect?
20. What does it mean to be amphipathic? Draw an example.
21. Draw a simple micelle. How do micelles work to remove greases and oils from
substances?
22. Identify two chaotropes, and describe what they do to nonpolar compounds in water.
23. Draw the hydrogen bonds likely to form between water and the following amino acid side
chains:
a. R
SH
O
b. R
NH2
24. Are the following compounds polar or amphipathic? Will they dissolve in water?
a. CH3(CH2)11COO–
b. CH3CH2NH3+
25. Water is _______________ because its __________ pairs attack _______________
during substitution or addition. It is a __________ nucleophile, but it’s concentration in
cells is so __________ that it could attack macromolecules, causing them to be
_______________.
26. Write an equation for the hydrolysis of the given dipeptide.
H
H
O
C
C
C
H
+
NH3
COO
N
C
H
H
-
CH2
27. Provide four reasons why all proteins are not destroyed by hydrolysis in the cell.
28. Write a mechanism for the self-ionization of water.
29. Calculate the concentration of pure water in 1 L of water. Use this and the ionization
constant for water (1.8 x 10–16 M) to calculate Kw.
30. Provide three examples of when the concentration of protons (_____) affects biochemical
processes.
31. What is physiological pH? What is the difference between acidosis and alkalosis?
32. Recalling that a strong acid completely _______________, calculate the concentration of
perchloric acid if the pH of the solution is 1.025.
33. Recalling that weak acids do not completely _______________, calculate the pKa of
carbonic acid if its Ka is 4 x 10–7.
34. Calculate the pH of 0.0500 M lactic acid (CH3CH(OH)COOH) if its pKa = 3.9.
35. Using the Henderson-Hasslebalch equation, explain the half-volume method of
determining pKa using titration.
36. Draw a generic titration curve of pH vs. volume of titrant for the titration of sulfurous
acid with potassium hydroxide. Sulfurous acid’s pKa values are 1.85 and 7.2.
37. When creating a buffer, the most effective buffering occurs when what two things are
equal?
38. Draw the equation for the buffer system that is responsible for regulating the pH of blood.
a. Explain how the buffer works when the pH of blood drops.
b. Explain how the buffer works when the pH of blood rises.
39. What two things help to buffer cells against pH changes? Other than the bicarbonate
system, what else helps to buffer the blood?
40. The pKa of 2-methoxybenzoic acid is 4.08. If 0.125 M of the acid and 0.125 M of the
conjugate base are available, calculate the volume of each required to make 250. mL of
buffer at a pH of 4.50.