BIOL 319 COHN FINAL EXAM
QUESTIONS AND ANSWERS GRADED A+
2025/2026
What are cells that must conduct action potential? - ANS excitable cells
what is the resting membrane potential/voltage for muscles? - ANS -85 mv
what is the sodium potassium pump also called - ANS sodium potassium ATPase
what does the sodium potassium pump have the ability to do - ANS take TP and hydrolyze it
into ADP and Pi
which direction does the sodium potassium pump move - ANS move sodium and potassium
in their opposite concentration gradient directions
what direction is sodium moving and how many - ANS 3 Na out
what direction is potassium moving and how many - ANS 2 K in
where do sodium and potassium have higher concentrations in the cell - ANS more Na
outside and more K inside (not equal distribution of ions)
1 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
,what do leakage channels do - ANS allow a given ion to leak down their concentration
gradient
why is the membrane never in danger of losing the gradient - ANS the sodium potassium
pump
which ion has significantly more channles? - ANS K+
where is potassium leaking to and from - ANS leaking from inside the cell to the outside
what are Pr- - ANS small charged particles that can't leave the cell (too big)
what partially neutralized Pr- - ANS K+
when K+ has the option to move down its concentration gradient, what happens - ANS it
abandons the neutralization of Pr-
what happens when Pr- loses its neutralization - ANS there is a negative charge distribution
that becomes too intense, so Pr- sucks the K+ back into the cell
which channel is the most impactful to setting the resting membrane potential - ANS the K+
leakage channels
what does the K+ channels cause the voltage of the cell to be? - ANS -90 mV
what cancels out some of the -90 mV caused by the K+ channels - ANS the Na+ leakage
channels because allowing a (+) ion to move down its concentration gradient in opposite
direction
2 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
, what do excitable cells use resting membrane potential as - ANS a launching pad for action
potential
the membrane right against the motor end plate and NMJ is guaranteed to what - ANS get
depolarized to -55mV
which voltage gated channel opens up faster, Na+ or K+ - ANS Na+
electrical potential = ____________? - ANS voltage
what is chemical potential also? - ANS the concentration gradient
what is depolarization associated with - ANS Na+ channels opening first
what is repolarization associated with - ANS Na+ channels closing at the same time the K+
channels open, creating the back half of the wave
what pump is the master for all action potential - ANS Na+/K+ pump
why can T-tubules conduct action potential - ANS the tubular involutions are lined with all
the channels necessary for AP
-they establish the resting membrane potential here to then conduct AP
what is a monovalent ion - ANS single ion with respective charge
when there is an overshoot of K+ causing hyperpolarization, who takes care of it -
ANS Na+/K+ pump
when AP is doing its job, which types of channels are working? - ANS VOLTAGE gated
channels, not leakage channels
3 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
QUESTIONS AND ANSWERS GRADED A+
2025/2026
What are cells that must conduct action potential? - ANS excitable cells
what is the resting membrane potential/voltage for muscles? - ANS -85 mv
what is the sodium potassium pump also called - ANS sodium potassium ATPase
what does the sodium potassium pump have the ability to do - ANS take TP and hydrolyze it
into ADP and Pi
which direction does the sodium potassium pump move - ANS move sodium and potassium
in their opposite concentration gradient directions
what direction is sodium moving and how many - ANS 3 Na out
what direction is potassium moving and how many - ANS 2 K in
where do sodium and potassium have higher concentrations in the cell - ANS more Na
outside and more K inside (not equal distribution of ions)
1 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
,what do leakage channels do - ANS allow a given ion to leak down their concentration
gradient
why is the membrane never in danger of losing the gradient - ANS the sodium potassium
pump
which ion has significantly more channles? - ANS K+
where is potassium leaking to and from - ANS leaking from inside the cell to the outside
what are Pr- - ANS small charged particles that can't leave the cell (too big)
what partially neutralized Pr- - ANS K+
when K+ has the option to move down its concentration gradient, what happens - ANS it
abandons the neutralization of Pr-
what happens when Pr- loses its neutralization - ANS there is a negative charge distribution
that becomes too intense, so Pr- sucks the K+ back into the cell
which channel is the most impactful to setting the resting membrane potential - ANS the K+
leakage channels
what does the K+ channels cause the voltage of the cell to be? - ANS -90 mV
what cancels out some of the -90 mV caused by the K+ channels - ANS the Na+ leakage
channels because allowing a (+) ion to move down its concentration gradient in opposite
direction
2 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
, what do excitable cells use resting membrane potential as - ANS a launching pad for action
potential
the membrane right against the motor end plate and NMJ is guaranteed to what - ANS get
depolarized to -55mV
which voltage gated channel opens up faster, Na+ or K+ - ANS Na+
electrical potential = ____________? - ANS voltage
what is chemical potential also? - ANS the concentration gradient
what is depolarization associated with - ANS Na+ channels opening first
what is repolarization associated with - ANS Na+ channels closing at the same time the K+
channels open, creating the back half of the wave
what pump is the master for all action potential - ANS Na+/K+ pump
why can T-tubules conduct action potential - ANS the tubular involutions are lined with all
the channels necessary for AP
-they establish the resting membrane potential here to then conduct AP
what is a monovalent ion - ANS single ion with respective charge
when there is an overshoot of K+ causing hyperpolarization, who takes care of it -
ANS Na+/K+ pump
when AP is doing its job, which types of channels are working? - ANS VOLTAGE gated
channels, not leakage channels
3 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
