Question Type: Essay
Chapter: 2
Application
Difficulty: Moderate
14. Cysteine often plays an important role in stabilizing protein structure. Explain how this works.
Ans: Two adjacent sulfhydryl (SH) groups can oxidize to form a covalent disulfide (S–S) bond. Disulfide bonds can stabilize the structure of folded peptides or sometimes link two separate peptide chains together.
Question Type: Essay
Chapter: 2
Blooms: Understanding
Difficulty: Easy
15. Triacylglycerol and cholesterol esters are nonpolar; in contrast, phospholipids are amphipathic molecules. Biomembranes are based on phospholipids rather than on triacylglycerols. Why?
Ans: Biomembranes are based on phospholipids rather than on triacylglycerols because phospholipids as amphipathic molecules can form planar lipid bilayers, whereas the nonamphipathic nonpolar triacylglycerols cannot. Their amphipathic property, the presence of a polar and nonpolar domain at opposite ends of the same molecule, allows phospholipids to form hydrophilic associations with water at the same time as forming hydrophobic associations with each other through their hydrophobic tails. Triacylglycerols are strictly hydrophobic in nature and hence in an aqueous environment tend to associate with one another to form lipid droplets. This minimizes the contact of triacylglycerol with water. Recall the old adage: oil and water do not mix.
Question Type: Essay
Chapter: 2
Blooms: Evaluating
Difficulty: Difficult
16. A nucleotide can vary in _____.
a. the base
b. the sugar
c. the phosphate group
d. the sugar and the base
Ans: d
Question Type: Multiple Choice
Chapter: 2
Blooms: Understanding
Difficulty: Moderate
17. Which of the following is NOT one of the ways RNA differs from DNA?
a. Ribonucleotides have a hydroxyl group on the 2 carbon of their sugar subunit.
b. Ribonucleotides can have enzymatic activity.
c. Ribonucleotides contain a phosphate group.
d. Ribonucleotides can contain the base uracil.
Ans: c
Question Type: Multiple Choice
Chapter: 2
Blooms: Remembering
Difficulty: Moderate
18. What is the major structural difference between starch and cellulose?
a. the types of monosaccharide subunits in the molecules
b. the amount of branching that occurs in the molecule
c. that humans can only ingest starch
d. the type of glycosidic linkages in the molecule
Ans: d
Question Type: Multiple Choice
Chapter: 2
Blooms: Understanding
Difficulty: Moderate
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19. How do phospholipids interact with water molecules?
a. The polar heads interact with water; the nonpolar tails do not.
b. Phospholipids don't interact with water because water is polar and lipids are nonpolar.
c. The polar heads avoid water; the nonpolar tails attract water (because water is polar and opposites attract).
d. Phospholipids dissolve in water.
Ans: a
Question Type: Multiple Choice
Chapter: 2
Blooms: Remembering
Difficulty: Easy
20. Which of the following is the BEST explanation for why vegetable oil is a liquid at room temperature while animal fats are solid?
a. Vegetable oil has fewer double bonds than animal fats.
b. Animal fats have no amphipathic character.
c. Vegetable oil has longer fatty-acid tails than do animal fats.
d. Vegetable oil has more double bonds than do animal fats.
Ans: a
Question Type: Multiple Choice
Chapter: 2
Blooms: Understanding
Difficulty: Easy
Section 2.3
21. A 1-mL solution of 0.05 M H2SO4 is diluted to 100 mL at 25°C. What is the pH of the resulting solution?
a. 1
b. 2
c. 3
d. 4
Ans: c
Question Type: Multiple Choice
Chapter: 2
Blooms: Applying
Difficulty: Moderate
22. An Archaea cell living in an abandoned mine is found to contain a very high concentration of protons. It is likely that this cell:
a. has a high ph and is acidic.
b. has a high ph and is alkaline.
c. has low ph and is acidic.
d. has a low pH and is alkaline.
Ans: c
Question Type: Multiple Choice
Chapter: 2
Blooms: Understanding
Difficulty: Easy
23. A 1-mL solution of 0.1 M NaOH is diluted to 1 L at 25°C. What is the pH of the resulting solution?