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Q
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Rationale
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1. A
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This structure
shows membranes studded with particles, the "classic" appearance of
rER
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2. 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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3. E
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All these
are membrane-bounded structures, and all membranes contain phospholipids.
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4. D
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-CH3 groups
are nonpolar, as are all hydrocarbons.
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5. A
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Definition
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6. A
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Any cell that
secretes protein must have lots of rER.
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7. B
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The nuclear
membrane is a double membrane.
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8. A
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Definition
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9. C
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Definition
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10. 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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11. 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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12. C
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Definition.
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13. A
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Proteins make
up 50% of the dry weight of a cell.
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14. B
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Remember CHNOPS!
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15. D
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The two molecules
shown are both amino acids -- they form a peptide bond.
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16. B
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Fatty acids
are the "monomers" for triglycerides, not hydrocarbons.
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17. E
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Rotate molecule
(a) upside down and it becomes (b); no isomers here!
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18. B
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Eukaryotes
are defined by the presence of a nucleus.
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19. 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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20. E
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Definition
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21. E
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Definition
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22. B
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Water dissociates
only weakly into H+ and OH-
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23. 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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24. D
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This example
was discussed in class.
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25. 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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26. A
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Molecule B
is a triglyceride containing 3 fully saturated fatty acids.
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27. D
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Fats have
approximately 2x the energy content of sugars
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28. D
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Molecule A
is clearly a sugar; counting the carbons shows 5, a pentose.
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29. A
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Definition.
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30. B
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Example discussed
in class.
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31. D
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Definition
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32. 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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33. A
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Hydrolysis
is defined as the process of breaking covalent bonds by adding water.
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34. C
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Starch is
the common plant soluble polysaccharide, similar to animal glycogen.
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35. A
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Definition.
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36. 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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37. E
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DNA is the
information transmitting molecule, not proteins.
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38. B
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There are
5 amino acids here, as indicated by circling them in the figure below:
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39. A
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No -SH groups
are present.
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40. A
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Definition
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41. C
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Since there
is a hydroxyl group, this will be a polar side chain
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42. B
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Definition
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43. 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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44. 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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45. 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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