Tbr bio q

[cloak25]

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If an azide (N3-) ion binds to the ferric iron in cytochrome oxidase, it blocks the last step of the mitochondrial electron transport chain. Immediately after the synthesis of ATP stops, the pH increases:


A. within the lumen of the stomach.
B. within the lumen of the duodenum.
C. outside the apical membrane.
D. within the parietal cell.
answer: C

Why is A wrong? isn't outside the apical membrane the lumen?

 

[Temperature101]

If an azide (N3-) ion binds to the ferric iron in cytochrome oxidase, it blocks the last step of the mitochondrial electron transport chain. Immediately after the synthesis of ATP stops, the pH increases:


A. within the lumen of the stomach.
B. within the lumen of the duodenum.
C. outside the apical membrane.
D. within the parietal cell.
answer: C

Why is A wrong? isn't outside the apical membrane the lumen?

Apical and lumen are kind of synonymous for inside....Basolateral is the outside. C is the correct answer since proton will stay inside the mitochondrial membrane. Inside will have a low pH and outside high pH.

 

[pm1]

Apical and lumen are kind of synonymous for inside....Basolateral is the outside. C is the correct answer since proton will stay inside the mitochondrial membrane. Inside will have a low pH and outside high pH.

wow.. I wouldn't know how to answer this question..
Wouldn't the increase in pH be in the mitochondria matrix?
My thought process being: if the last step is blocked than the protons wouldn't be able to go back from the inter membrane space to the matrix (making ATP in the process). Hence, less H+ in the matrix increasing it's pH. Is that wrong?

And how do you translate that into looking at the membrane of the cell?

I'm confused.. 😕

thank you!!

 

[FutureDoc2]

wow.. I wouldn't know how to answer this question..
Wouldn't the increase in pH be in the mitochondria matrix?
My thought process being: if the last step is blocked than the protons wouldn't be able to go back from the inter membrane space to the matrix (making ATP in the process). Hence, less H+ in the matrix increasing it's pH. Is that wrong?

And how do you translate that into looking at the membrane of the cell?

I'm confused.. 😕

thank you!!

I agree. Am I missing something? Someone care to chime in?

 

[Temperature101]

wow.. I wouldn't know how to answer this question..
Wouldn't the increase in pH be in the mitochondria matrix?
My thought process being: if the last step is blocked than the protons wouldn't be able to go back from the inter membrane space to the matrix (making ATP in the process). Hence, less H+ in the matrix increasing it's pH. Is that wrong?

And how do you translate that into looking at the membrane of the cell?

I'm confused.. 😕

thank you!!

Come to think of it, you might be right. I think A might be the right answer... Someone else should chime on it..

 

[Incontrol]

Bump, I know this is an old post. But I have the same question on this. Why C and not A? is it because C is a more immediate change than A? because outside the apical membrane is a reference to a relatively smaller location than the whole stomach lumen?

 

[image187]

if you poison the electron transport chain of a parietal cell, the cell eventually dies and can no longer perform its function of secreting H+ into the gastric lumen. This would first result in a local increase in pH outside of the apical membrane

 

[Incontrol]

if you poison the electron transport chain of a parietal cell, the cell eventually dies and can no longer perform its function of secreting H+ into the gastric lumen. This would first result in a local increase in pH outside of the apical membrane

whats the distinction between apical membrane and stomach lumen?

 

[image187]

apical means the side facing the outside, while the lumen is defined as the internal cavity bound byecho surrounding cells. If you look at the histology of the gastric mucosa, the parietal cells are located within "gastric pits", and their apical membranes don't actually make contact with the gastric lumen at all.

 

[Incontrol]

apical means the side facing the outside, while the lumen is defined as the internal cavity bound byecho surrounding cells. If you look at the histology of the gastric mucosa, the parietal cells are located within "gastric pits", and their apical membranes don't actually make contact with the gastric lumen at all.

Got it! thanks

 

[sdm33]

If an azide (N3-) ion binds to the ferric iron in cytochrome oxidase, it blocks the last step of the mitochondrial electron transport chain. Immediately after the synthesis of ATP stops, the pH increases:

Is this Q Part of a passage?? Because Sodium Azide can kill you by blocking the Mitochondria anywhere in the body, it does not have to be the stomach.

A. within the lumen of the stomach. even tho Lumen is too far, indirectly it will have less acid.
B. within the lumen of the duodenum.
C. outside the apical membrane. yes
D. within the parietal cell. but why D is wrong ???

 

[Incontrol]

If an azide (N3-) ion binds to the ferric iron in cytochrome oxidase, it blocks the last step of the mitochondrial electron transport chain. Immediately after the synthesis of ATP stops, the pH increases:

Is this Q Part of a passage?? Because Sodium Azide can kill you by blocking the Mitochondria anywhere in the body, it does not have to be the stomach.

A. within the lumen of the stomach. even tho Lumen is too far, indirectly it will have less acid.
B. within the lumen of the duodenum.
C. outside the apical membrane. yes
D. within the parietal cell. but why D is wrong ???

Why do you think the inside of parietal cells would have an increase in pH before the outside of the apical membrane?

and yes this is part of a passage and it has a figure where it showed a parietal cell and different channels /ports and their function.

 

[image187]

If an azide (N3-) ion binds to the ferric iron in cytochrome oxidase, it blocks the last step of the mitochondrial electron transport chain. Immediately after the synthesis of ATP stops, the pH increases:

Is this Q Part of a passage?? Because Sodium Azide can kill you by blocking the Mitochondria anywhere in the body, it does not have to be the stomach.

A. within the lumen of the stomach. even tho Lumen is too far, indirectly it will have less acid.
B. within the lumen of the duodenum.
C. outside the apical membrane. yes
D. within the parietal cell. but why D is wrong ???

If a cell is subjected to some insult that interfered with oxidative metabolism/aerobic respiration, such as messing around with the mitochondria or electron transport chains, the cell will switch to anaerobic respiration, reducing pyruvate to lactic acid. When starved from oxygen like this, this acidosis (decreased pH) will lead to altered cellular metabolism (as enzymes function optimally in a certain physiologic pH), disrupted Na/K pumps, dysfunctional electrolyte concentrations, and eventually cellular death.

 

[image187]

If an azide (N3-) ion binds to the ferric iron in cytochrome oxidase, it blocks the last step of the mitochondrial electron transport chain. Immediately after the synthesis of ATP stops, the pH increases:

Is this Q Part of a passage?? Because Sodium Azide can kill you by blocking the Mitochondria anywhere in the body, it does not have to be the stomach.

A. within the lumen of the stomach. even tho Lumen is too far, indirectly it will have less acid.
B. within the lumen of the duodenum.
C. outside the apical membrane. yes
D. within the parietal cell. but why D is wrong ???

If a cell is subjected to some insult that interfered with oxidative metabolism/aerobic respiration, such as messing around with the mitochondria or electron transport chains, the cell will switch to anaerobic respiration, reducing pyruvate to lactic acid. When starved from oxygen like this, this acidosis (decreased pH) will lead to altered cellular metabolism (as enzymes function optimally in a certain physiologic pH), disrupted Na/K pumps, dysfunctional electrolyte concentrations, and eventually cellular death.

 

[sdm33]

Thanks, Under normal Conditions the parietal cell, secretes HCl which can have a pH as low as 1.5. Parietal cells are acidophilic because they contain a large number of mitochondria. The mitochondria, which are needed to pump hydrogen ions against their concentration gradient, are acidophilic; therefore, parietal cells are acidophilic as well. If mitochondria is blocked then the parietal cell will become less acidic and will have a higher pH.
Are you saying D is wrong because the cell death??

 

[Incontrol]

Thanks, Under normal Conditions the parietal cell, secretes HCl which can have a pH as low as 1.5. Parietal cells are acidophilic because they contain a large number of mitochondria. The mitochondria, which are needed to pump hydrogen ions against their concentration gradient, are acidophilic; therefore, parietal cells are acidophilic as well. If mitochondria is blocked then the parietal cell will become less acidic and will have a higher pH.
Are you saying D is wrong because the cell death??

Let me take a stab at this.

function of Mitochondria in normal condition:

You pump H+ into inter-membrane space and H+ will come down through the gradient by ATP synthase and go back to mitochondria's matrix.

Function under cytchrome oxidase:

You pump H+ into inter-membrane space but since cytochrome oxidase is blocked the electrons can't complete the electron transport chain. This will cause the electron chain reaction to be blocked and it will back fill quickly (because you can't dispose of those e- into water). The mitochondria will no longer be able to pump H+ into the inter-membrane because you have too much of the product (e-) already in there (NADH ----> NAD+ + e- + H reaction CANNOT occur).

Overall this will stop the inter-membrane of having H+ gradiant, so ATP synthase can't do its job anymore. If you notice, this will not cause the mitochondria to be less acidic. In fact it might be a bit more acidic ( the reason why it's only a bit. because the overall inter-membrane space is smaller than the matrix, thus the effect is not on a grand level, as far as I know)).

Now, parietal cells pump H+ into the apical membrane by using H+/K+ pump (Which uses ATP). since you don't produce ATP anymore you can't pump those H+ outside. Which causes the cell to be EVEN more acidic.


Note: you don't need to know the specific H+/K+ pump it was explained in passage. But you do need to know that you use Active energy to pump H+ out.
You also need to know what happens in ETC exactly when you block different things (block ATP synthase vs blocking a cytochrome vs changing the inter-membrane space permeability)

I just woke up. Hopefully this will make sense.

 

[sdm33]

Crystal ..........
If I have seen further it is by standing on the shoulders of giants

 

[Incontrol]

Crystal ..........
If I have seen further it is by standing on the shoulders of giants

You make me blush. Now if I could only break a 30

 

[image187]

You make me blush. Now if I could only break a 30

You can!! don't give up