If there are “CUES” listed within the question, please USE them and UNDERLINE them in your answer!
Chapter 9
1.The basic formula for a carbohydrate is CH2O. Why, then, does glucose (C6H12O6) follow this formula but sucrose
(C12H22O11) does not? Explain. (CUES: water molecule, bond formation, dehydration synthesis)
2. The evolution of photosynthesizing organisms on Earth and the development of an oxygen-rich environment led
to a rapid diversification of life. Explain why there is an evolutionary advantage to an organism that requires
oxygen to live compared to one that does not require oxygen. (CUES: glucose, Krebs cycle, oxidative
phosphorylation, ATP, efficiency)
3. Use Figures 9.6 & 9.11 to answer the following questions. Under laboratory conditions muscle cells were broken
up and separated into fractions of mitochondria and cytoplasm in an attempt to learn more about cellular
respiration. Each fraction was incubated with glucose or pyruvate. Tests were carried out during incubation for
the presence of either carbon dioxide or lactic acid. The results are shown below:
Cell Fraction
CO2
Lactic Acid
Mitochondria incubated with glucose
Absent
Absent
Mitochondria incubated with pyruvate
Present
Absent
Cytoplasm incubated with glucose
Absent
Present
Cytoplasm incubated with pyruvate
Absent
Present
a. What does the presence of lactic acid in a sample indicate about what process is occurring in each cell
fraction?
b. Explain why lactic acid was produced by the cytoplasm fraction incubated with glucose, but not the
mitochondrial fraction.
c. Why was no carbon dioxide produced by either fraction incubated with glucose?
4. Explain how the two different membrane-embedded proteins in mitochondria—proton pumps and ATP synthase—
simultaneously influence the gradient of hydrogen ions and ATP synthesis. (CUES: NADH, FADH2, ATP, electrons,
H+, proton pump, oxygen, water, inner mitochondrial membrane, matrix, intermembrane space)
5. Compare the two mechanisms that generate ATP in cellular respiration—substrate-level phosphorylation and
chemiosmotic phosphorylation. In what stage(s) of cellular respiration does each occur? Where does each get the
energy for making ATP? Which produces the most ATP under aerobic conditions? Under anaerobic conditions?
(CUES: electron transport chain, ATP synthase, glycolysis, Krebs cycle, H +, enzyme, ATP, ADP)
6. Without oxygen, cellular respiration grinds to a standstill, although glycolysis can continue to make some ATP
anaerobically for a short time. When oxygen runs out, why does electron transport stop? Why does the Krebs
cycle stop? (CUES: electrons, electronegative, attract, NADH, FADH 2, NAD+, FAD)
7. Several units ago, we learned that membranes must be fluid to function properly. How does the operation of the
electron transport chain support that thought? (CUES: inner mitochondrial membrane, integral proteins,
phospholipid bilayer)
8. A typical, active young man requires 2,800 kilocalories of food energy a day to fuel metabolism, movement, active
transport, etc. The energy stored in the third phosphate bond of ATP is 0.0145 kcal/gram. If the energy from
the man’s food were all stored as ATP, how much ATP would be produced each day from ADP and Pi? The man
actually has about 50 grams of ATP. What does this mean in terms of ATP hydrolysis and synthesis?
9. Use p. 177 in your textbook to answer the following: Trace the biochemical pathway by which a carbon atom
from a starch molecule in rice eaten today can end up in a muscle protein tomorrow. (CUES: pyruvate, amino acid,
protein, Krebs cycle, glycolysis, glucose, starch)
10. Use Figure 9.15 to answer the following: In the absence of oxygen, what do you think would happen if you
decreased the pH of the intermembrane space of the mitochondrion. Explain your answer. (CUES: H+,
concentration gradient, chemiosmosis, ATP synthase, ATP)
11. A glucose-fed yeast cell is moved from an aerobic environment to an anaerobic one. Specifically, how would its
rate of glucose consumption change if ATP were to be generated at the same rate? Why?
12. Use Figure 9.19 to explain the following: During intense exercise, why can’t a muscle cell efficiently use fat as a
concentrated source of chemical energy? (CUES: glycolysis, Krebs’ cycle, oxidative phosphorylation, aerobic
respiration, anaerobic respiration, beta oxidation)
Chapter 21
1. What is a homeotic gene? Why does a mutation in a homeotic gene have a much more drastic effect on the
organism than a mutation in other genes? (CUES: body plan, segmentation, protein, activators, repressors)
2. Describe how liver, muscle, and salivary gland cells are specialized for different functions. How do their
differences reflect differences in gene expression? Suggest a gene that might be active in each of the cells but
none of the others. Suggest a gene that might be active in all the cells. Suggest a gene that is probably not active
in any of the cells. (CUES: activator proteins, repressor proteins, regulatory genes, shape, function)
3. Molecular biologists can attach genes to active promoters and insert them into cells. This results in higher than
normal expression (overexpression) of the genes. What do you think would happen in each of the following cases if
the genes listed would be overexpressed in the specified tissues. Explain your answers.
a. ced-3 in embryonic neuron precursors of C. elegans (Figure 21.18)
b. myoD in undifferentiated myoblasts (Figure 21.10)
4. The control of eye formation during the development of many animals is under the control of a genetic switch
involving a transcription factor. Partial DNA sequences for the control gene from two organisms are given below:
Mouse Pax6 gene:
5’-GTA TCC AAC GGT TGT GTG AGT AAA ATT-3’
Fruit fly eyeless gene:
5’-GTA TCA AAT GGA TGT GTG AGC AAA ATT-3’
a. Calculate the percentage of identity (the percentage of bases that are identical) between the two DNA
sequences.
b. Use the genetic code (page 314) to determine the amino acid sequences encoded by the two regions and
calculate the percentage of identity between the two amino acid sequences.
c. The fruit fly and the mouse diverged from a common ancestor about 500 million years ago. Comment on
your answers to ‘a’ and ‘b’ in terms of the evolution of developmental pathways. What type of mutations in
the gene are present? Why?
5. As you learned in Chapter 12, mitosis gives rise to two daughter cells that are genetically identical to the parent
cell. Yet you, the product of many mitotic cell divisions, are not composed of identical cells. Why? (CUES:
differentiation, stem cells, differential gene expression, activators)
6. In Figure 47.25 (Chapter 47), the transplanted dorsal lip caused the recipient tissue to become something else it
otherwise would not have become. What does this indicate? (CUES: ligand, receptor, transduction pathway,
transcription, translation, differentiation, induction)
7. Figure 21.14 shows the importance of morphogen gradients during development. Predict what would happen if
researchers injected bicoid mRNA into the anterior end of an egg from a female with a mutation disabling the
bicoid gene.