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Q.
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Rationale
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1. A
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Proteins
make up 50% of the dry weight of a cell.
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2. B
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Remember
CHNOPS!
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3. D
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The two
molecules shown are both amino acids -- they form a peptide bond.
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4. B
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Fatty
acids are the "monomers" for triglycerides, not hydrocarbons.
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5. E
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Rotate
molecule (a) upside down and it becomes (b); no isomers here!
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6. B
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Eukaryotes
are defined by the presence of a nucleus.
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7. C
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C-14 must
have two more heavy nuclear particles than C-12; if there were two extra
protons, this would no longer be Carbon but Oxygen.
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8. E
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Definition
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9. E
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Definition
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10. B
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Water
dissociates only weakly into H+ and OH-
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11. A
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pH is
a logarithmic scale; each downward step (e.g. 7 to 6) corresponds to
a tenfold increase in H+ ions.
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12. D
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This example
was discussed in class.
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13. A
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Structural
isomers because the carbonyl group is in a recognizably different position
(like moving one blue bead in an otherwise red chain from the end to
an interior position).
Note: the right figure in the exam included an unintended typo, an extra H atom attached to the keto group. This was corrected during the exam in the AS 55 classroom. Unfortunately, one of the proctors didn't show up, so I had to stay in AS 55 and couldn't go back to TLS 154 to announce the correction. |
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14. A
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Molecule
B is a triglyceride containing 3 fully saturated fatty acids.
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15. D
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Fats have
approximately 2x the energy content of sugars
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16. D
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Molecule
A is clearly a sugar; counting the carbons shows 5, a pentose.
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17. A
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Definition.
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18. B
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Example
discussed in class.
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19. D
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Definition
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20. A
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This is
a buffer. When OH- ions are added, more carbonic acid and bicarbonate
will dissociate to release H+, to combine with OH- and keep pH stable.
As this happens, the % of carbonate ion must increase.
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21. A
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Hydrolysis
is defined as the process of breaking covalent bonds by adding water.
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22. C
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Starch
is the common plant soluble polysaccharide, similar to animal glycogen.
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23. A
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Definition.
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24. C
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Enzymes
work without needing an external energy source; by rearranging electrons
they lower activation energies that prevent reactions from ocurring
rapidly.
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25. E
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DNA is
the information transmitting molecule, not proteins.
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26. B
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There
are 5 amino acids here, as indicated by circling them in the figure
below:
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27. A
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No -SH
groups are present.
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28. A
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Definition
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29. C
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Since
there is a hydroxyl group, this will be a polar side chain
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30. B
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Definition
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31. B
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Allosteric
enzymes are more complex and "expensive" for the cell to build
-- they typically occur only in the first step of a series of enzyme-mediated
synthetic reactions.
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32. A
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Disulfide
bonds are important in helping to maintain the stability of both 3o
and 4o structure.
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33. A
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The size
of a delta G tells you nothing about how fast the reaction will proceed.
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34. A
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This structure
shows membranes studded with particles, the "classic" appearance of
rER
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35. A
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Letter
"l" is pointing to the big densely stained body in the nucleus; this
must be the nucleolus.
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36. E
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All these
are membrane-bounded structures, and all membranes contain phospholipids.
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37. D
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-CH3 groups
are nonpolar, as are all hydrocarbons.
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38. A
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Definition
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39. A
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Any cell
that secretes protein must have lots of rER.
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40. B
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The nuclear
membrane is a double membrane.
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41. A
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Definition
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42. C
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Definition
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43. C
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(c) is
the only molecule that looks 'funny' - it doesn't appear to display
the correct valence for Carbon. The only way to account for this structure
is if there is a triple bond linking the two C atoms.
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44. A
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It's obviously
a fatty acid (hydrocarbon + carboxyl group), and since there's a double
bond it is by definition unsaturated.
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45. C
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Definition.
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