(Here you will find answer keys for homework or quizzes as well as unedited responses on exams from your classmates)




1.  The K ion channel is an example of how molecules are transferred across the phospholipid bilayer by the process of

            a.         simple diffusion

            b.         facilitated transport

            c.         secondary active transport

            d.         primary active transport



2.  If you placed one of your cheek cells (given: The ICF = 170 mM NaCl ) in a solution of 300 mM glucose, and you assume neither compound could permeate the PL bilayer, through the process of osmosis your cell would

            a.         crenate

            b.         lyse

            c.         be happy as a clam (normal cell volume)

            d.         cannot determine by the provided information



3.  The Na/K ATPase pump uses a method called __________________   __________________

or successive phosphorylation/dephosphorylation cycles to change its configuration and pump ions against their concentration gradients.

ANSWER:  Molecular Peristalsis


4.  T or F   (please circle)


If a cell has an electrical disturbance of at least 30 mV, it will always fire an action potential because of the ALL-or-NONE principle.



5.  Which of the following physiological processes requires no ATP expenditure?

            a.         endocytosis

            b.         exocytosis

            c.         osmosis

            d.         facilitated diffusion

            e.         two of the above



6.  Which of the following organic molecules would be classified as a protein?

            a.         molecules that are formed from dehydration reactions

            b.         molecules that contain free fatty acids

            c.         molecules that are produced from peptide bond formations

            d.         steroids

            e.         DNA

            f.          glycogen

            g.         ketone bodies


7.  If a cell had the following ionic concentrations and permeabilities, about at what voltage would you predict an action potential would change polarity (peak of the action potential spike)?

HINT: You can decide whether to use Nernst or Goldman.


PK = 10

PNa = 10,000

Assume mammalian temperature of 37 degrees.

[K+]o = 40 mM

[K+]i = 365 mM

[Na+]o = 420 mM

[Na+]i = 65 mM


Please show all calculations.                          Answer: ______________________________



ANSWER:  You can use either Nernst or Goldman, but of course the former is less time consuming.


ENa = 60 log (420/65) = 49 mV

Em = 60 log[ [(10,000)420 + 10(40)]/[(10,000)65 + 10(365)] = 49 mV      


8.  If the resting potential of the cell in #7 was -85 mV, at what voltage would this action potential begin to fire fully?     HINT: Threshold.




Please show all calculations.                          Answer: _________________________________


ANSWER:    Th = 0.15 (Amplitude)

Amplitude = -85  mV  to 49 mV = a delta of 134 mV

134 * 0.15 =  20 mV

If the resting potential is -85 mV and you have to  calculate the voltage at which the AP would fire fully, then  add 20 mV to -85 mV =  -65 mV



9.  Write one sentence describing the importance of the phospholipid bilayer for the physiologist =



ANSWER:  Many things here!


10.  T or F (please circle)


According to Fick’s Law of Diffusion, the diffusion rate or flux is greatest when the molecule to be transported has a high molecular weight and has to traverse a large cross-sectional area.




11.  If an action potential (AP) reaches threshold, where in the neuron will the AP “spike” be initiated?

            a.         the dendrite

            b.         the soma

            c.         the axon hillock

            d.         the synaptic terminals

            e.         the sodium/potassium ATPase pump