Download Unit 2 Practice Questions

Unit 2 Practice Questions
1. Imagine an elongated cell (such as a nerve cell) that measures 125x1x1 arbitrary units. Predict how its surface
area-to-volume ratio would compare with those in Figure 6.7 (pg. 99). Then calculate the ratio and check your
prediction.
2. Describe the role of transport vesicles in the endomembrane system.
3. The carbohydrates attached to some proteins and lipids of the plasma membrane are added as the membrane is
made and refined in the ER and Golgi apparatus. The new membrane then forms transport vesicles that travel to
the cell surface. On which side of the vesicle membrane are the carbohydrates?
4. What happens to a cell placed in a hypertonic solution? Describe the free water concentration inside and out.
5. If a Paramecium caudatum cell swims from a hypotonic to an isotonic environment, will its contractile vacuole
become more active or less? Why?
6. As a cell grows, its plasma membrane expands. Does this involve endocytosis or exocytosis? Explain.
7. An experiment is designed to study the mechanism of sucrose uptake by plant cells. Cells are immersed in a
sucrose solution, and the pH of the solution is monitored with a pH meter. Samples of the cells are taken at
intervals, and the sucrose in the sampled cells is measured. The measurements show that sucrose uptake by the
cells correlates with a rise in the pH of the surrounding solution. The magnitude of the pH change is proportional
to the starting concentration of sucrose in the extracellular solution. A metabolic poison known to block the ability
of cells to regenerate ATP is found to inhibit the pH changes in the extracellular solution. Based on this
information which of the following statements would you predict is correct?
a. Sucrose uptake is the result of simple diffusion.
b. Hydrogen ion movement is the result of facilitated diffusion.
c. Sucrose moving through the membrane forces hydrogen ions in to the cell.
d. Sucrose and Hydrogen ions are transported in opposite directions across the membrane.
e. Sucrose transport is the result of a hydrogen ion cotransporter.
8. An artificial cell consisting of an aqueous solution enclosed in a selectively permeable membrane has just been
immersed in a beaker containing a different solution. The
membrane is permeable to water and to the simple sugars glucose
and fructose but completely impermeable to the disaccharide
sucrose.
a. Which solute(s) will exhibit a net diffusion into the cell?
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b. Which solute(s) will exhibit a new diffusion out of the cell?
c. Is the solution outside the cell isotonic, hypotonic, or
hypertonic?
d. In which direction will there be a net osmotic movement of
water?
e. After the cell is placed in the beaker, which of the following
changes will occur? (choose all that apply)
i. The artificial cell will become more flaccid.
ii. The artificial cell will become more turgid.
iii. Some water molecules will flow out of the cell, but the majority will flow into it.
iv. The membrane potential will decrease.
v. In spite of the inability of sucrose to cross the membrane, eventually the two solutions will have
the same solute concentrations.
9. The solutions in the arms of a U-tube are separated at the bottom
of the tube by a selectively permeable membrane. The
membrane is permeable to sodium chloride but not to glucose.
Side A is filled with a solution of 0.4 M glucose and 0.5 M sodium
chloride (NaCl), and side B is filled with a solution containing 0.8
M glucose and 0.4 M sodium chloride. Initially, the volume in both
arms is the same. Refer to the figure to answer the following
questions.
At the beginning of the experiment, side A
A) is hypertonic to side B.
B) is hypotonic to side B.
C) is isotonic to side B.
D) is hypertonic to side B with respect to glucose.
E) is hypotonic to side B with respect to sodium chloride.
If you examine side A after three days, you should find
A) a decrease in the concentration of NaCl and glucose and an increase in the water level.
B) a decrease in the concentration of NaCl, an increase in water level, and no change in the
concentration of glucose.
C) no net change in the system.
D) a decrease in the concentration of NaCl and a decrease in the water level.
E) no change in the concentration of NaCl and glucose and an increase in the water level.
10. You observe plant cells under a microscope that have just been placed in an unknown solution. First the cells
plasmolyze; after a few minutes, the plasmolysis reverses and the cells appear normal. What would you conclude
about the unknown solute?
a. It is hypertonic to the plant cells, and its solute can not cross the pant cell membranes.
b. It is hypotonic to the plant cells, and its solute can not cross the pant cell membranes.
c. It is isotonic to the plant cells, but its solute can cross the plant cell membranes.
d. It is hypertonic to the plant cells, but its solute can cross the plant cell membranes.
e. It is hypotonic to the plant cells, but its solute can cross the plant cell membranes.
QuickTime™ and a
decompressor
are needed to see this picture.
QuickTime™ and a
decompressor
are needed to see this picture.
QuickTime™ and a
decompressor
are needed to see this picture.