does the real DAT have dumb questions like this?

[polkadds]

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During the early phase of an action potential A. Na+ moves out of cell and K+ moves in.
B. Na+ moves into the cell and K+ moves out.
C. Only Na+ moves
D. Only K+ moves
E. Only Ca+ moves



The Best answer is C, but in all reality B is also correct because K+ is always moving.



Does the real DAT have answers that are clear as mud like this, or do they usually have 1 clear answer.

 

[slm266]

Sounds pretty straight forward from what I learned in physiology.

I learned that na entering and k exiting were distinct phases when it comes to fast response in cardiac muscle
phase 0: rapid upstroke (na influx)
phase 1: early depolarization (k efflux)
phase 2: plateau (balance of ca influx/k efflux)
phase 3: final repolarization
phase 4: normal resting potential

 

[polkadds]

yea, but it is a little misleading due to the fact that K+ is permeable to the membrane so it is always moving in/out to a certain degree.

 

[nyr201]

im with you polk, K+ always moves in and out through K+ leakage channels keeping the membrane at the resting potential, that question is terrible i hope the real dat isn't like this lol.

 

[slm266]

For the action potential, we are talking about a voltage gated k-channel, and the key phrase is EARLY PHASE. Google search "action potential graph". Campbells also has a good explanation of action potentials. The other choice is close to being correct because both gates begin to open once it reaches threshold, but the k+ gate opens very slowly. Thus, na rushes in "first", and once the k+ gate opens more over time, it allows k+ to efflux.

The question seems very fair. What is the source of the question?

 

[mprs]

did you hack into my DAT test?

 

[achilles2]

lulz at all the people in this thread who understand so little cell bio they can't comprehend what the op is annoyed about.


OK here it goes....

at ALL times the cell is SLIGHTLY perm to K+ (K+ leak channels) these leak channels establish the resting membrane potential of a cell (and the constant activity of the Na/K ATPase)

NOW during the early phase of an AP voltage gated Na+ channels open....BUT since the cell is ALWAYS perm to K+ it means Na+ is rushing in and K+ is leaving, however, since the K+ leak level is so insignificant to the Na+ influx is can basically be ignored.

Now this questions most likely correct answer is only Na+ channels are open, however, if you actually understand cell bio you would be rightfully confused because you would want to take into account the K+ leak channels thus making this a frustrating question.


To the op:

On my DAT I didn't see any borderline questions like that but its possible that they may put something in that could have a gray area answer. I wouldn't worry about it to much odds are the questions will be straight forward. And since you understand what K+ leak channels are it sounds like your molecular bio is on point. I'd start reviewing all the general random things like taxonomy to get on point.

 

[polkadds]

lulz at all the people in this thread who understand so little cell bio they can't comprehend what the op is annoyed about.


OK here it goes....

at ALL times the cell is SLIGHTLY perm to K+ (K+ leak channels) these leak channels establish the resting membrane potential of a cell (and the constant activity of the Na/K ATPase)

NOW during the early phase of an AP voltage gated Na+ channels open....BUT since the cell is ALWAYS perm to K+ it means Na+ is rushing in and K+ is leaving, however, since the K+ leak level is so insignificant to the Na+ influx is can basically be ignored.

Now this questions most likely correct answer is only Na+ channels are open, however, if you actually understand cell bio you would be rightfully confused because you would want to take into account the K+ leak channels thus making this a frustrating question.


To the op:

On my DAT I didn't see any borderline questions like that but its possible that they may put something in that could have a gray area answer. I wouldn't worry about it to much odds are the questions will be straight forward. And since you understand what K+ leak channels are it sounds like your molecular bio is on point. I'd start reviewing all the general random things like taxonomy to get on point.

Thanks achilles, thats just what I was looking/hoping for!

 

[slm266]

no need to attack with arrogance

When you talk about "leak channels" are you talking voltage gated channels or chemically gated ion channels. There are a few K channels that open/close throughout the action potential period: the Transient Out channel that opens slowly at threshold, the Inward Rectifier which sets the resting membrane potential, and the Delayed Rectifier.

I refer to the voltage-gated channels which open once the cell reaches threshold potential, Transient Out. (The k+ voltage-gated channel is not always open, but only opens during depolarization). Once it opens, k+ trickles out as Na gushes in due to wide Na+ gates. The distinct Na (depolarization) and then K (repolarization) peaks is due to the speed of the inactivation gates. The slow response of the K inactivation gate ultimately results in hyperpolarization.

I understand that at an intermediate phase you have both Na rushing in as K rushes out, but the former defines the early phase of action potential.

 

[slm266]

The initial upward spike in membrane potential is due only to the influx of Na. As the activation gates are open, the potassium channels remain closed.

Campbells Bio 6e p1030

 

[DeathNote]

During the early phase of an action potential A. Na+ moves out of cell and K+ moves in.
B. Na+ moves into the cell and K+ moves out.
C. Only Na+ moves
D. Only K+ moves
E. Only Ca+ moves



The Best answer is C, but in all reality B is also correct because K+ is always moving.



Does the real DAT have answers that are clear as mud like this, or do they usually have 1 clear answer.

You are just looking too deep into the question--- the questions will be straightforward and I believe this is a fair question--Na rushes in first read it every time I learned about action potentials

 

[nyr201]

lulz at all the people in this thread who understand so little cell bio they can't comprehend what the op is annoyed about.


OK here it goes....

at ALL times the cell is SLIGHTLY perm to K+ (K+ leak channels) these leak channels establish the resting membrane potential of a cell (and the constant activity of the Na/K ATPase)

NOW during the early phase of an AP voltage gated Na+ channels open....BUT since the cell is ALWAYS perm to K+ it means Na+ is rushing in and K+ is leaving, however, since the K+ leak level is so insignificant to the Na+ influx is can basically be ignored.

Now this questions most likely correct answer is only Na+ channels are open, however, if you actually understand cell bio you would be rightfully confused because you would want to take into account the K+ leak channels thus making this a frustrating question.


To the op:

On my DAT I didn't see any borderline questions like that but its possible that they may put something in that could have a gray area answer. I wouldn't worry about it to much odds are the questions will be straight forward. And since you understand what K+ leak channels are it sounds like your molecular bio is on point. I'd start reviewing all the general random things like taxonomy to get on point.

thanks for expanding on the leakage channels lol good stuffs

 

[achilles2]

no need to attack with arrogance

When you talk about "leak channels" are you talking voltage gated channels or chemically gated ion channels. There are a few K channels that open/close throughout the action potential period: the Transient Out channel that opens slowly at threshold, the Inward Rectifier which sets the resting membrane potential, and the Delayed Rectifier.

I refer to the voltage-gated channels which open once the cell reaches threshold potential, Transient Out. (The k+ voltage-gated channel is not always open, but only opens during depolarization). Once it opens, k+ trickles out as Na gushes in due to wide Na+ gates. The distinct Na (depolarization) and then K (repolarization) peaks is due to the speed of the inactivation gates. The slow response of the K inactivation gate ultimately results in hyperpolarization.

I understand that at an intermediate phase you have both Na rushing in as K rushes out, but the former defines the early phase of action potential.

I apologize.

I just got annoyed when people were saying how it was a obvious simple problem and didn't see where the op was coming from.

My bad =/

 

[KittySquared]

I think this is pretty straightforward too. My answer was C before I saw you posted the answer. At first ONLY Na+ moves. I know that K+ moves too, but Na+ goes FIRST.