14. The diagram shows a model cell that transports
substance X across the cell membrane. The cell is
equipped with a Na-K-ATPase pump as shown.
Substance X enters the cell by a coupled transport
mechanism and exits the cell by carrier-mediated
diffusion. Treatment with a substance that inhibits the
Na-K-ATPase pump inhibits the transport of X by
which of the following mechanisms?
A. Decreasing intracellular K+ concentration
B. Decreasing intracellular Na+ concentration
C. Increasing intracellular K+ concentration
D. Increasing intracellular Na+ concentration
15. The diagram shows a bag (with permeability characteristics similar to
that of a normal cell) that contains a 100 mM solution of urea at time
zero. The bag is placed in a beaker containing 100 mM glucose.
Which of the following best describes the tonicity and osmolarity of
the glucose solution as well as any changes in bag volume (assume
that the bag volume is infinitely small compared to beaker volume)?
Osmolarity Tonicity Bag volume
A. Hyperosmotic Hypertonic Decreases
B. Hyperosmotic Hypotonic Increases
C. Hyperosmotic Isotonic No change
D. Hypoosmotic Hypotonic Decreases
E. Hypoosmotic Isotonic Increases
F. Hypoosmotic Hypertonic No change
G. Isoosmotic Hypertonic Decreases
H. Isoosmotic Hypotonic Increases
I. Isoosmotic Isotonic No change