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A2 Biology | Post your doubts here

L

larina

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I've got a big confusion about proximal convoluted tubule
Please tell me if i'm correct. This is what I think
-Sodium ions are actively pumped out from the basal membrane of tubule into the blood capillary
-This creates a concentration gradient between the lumen of the tubule and the blood capillary
-Na+ diffuses from the lumen to the capillary(by facilitated diffusion) through a cotransporter that carries glucose as well
-So glucose and Na+ diffuse into the blood capillary and the concentration of ions decrease in the tubule, so water follows by osmosis..


...And this is what mark scheme says...
Na+ actively transported (out of cell) into blood ;
creates concentration gradient ;
Na+ enters cell by diffusion ;
through cotransporter / symporter proteins ;
glucose cotransported / facilitated diffusion (from lumen to cells) ;
glucose diffuses into blood capillaries ;

I dont get what is 'cell' over here, is it the tubule or the blood capillary???
 
angelgirl:)

angelgirl:)

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user said:
angelgirl:) hassam alphabravocharlie

firstly, assalamoalaikum wr wb to u all..

Well you people asked about describing graphs.
Just remember one thing.. ‘describing a graph’ is the best part cuz u just have to tell what the graph shows and u need not worry about why it is so [unless they ask you to explain]...so u get 3-4 marks for free ;) (y)
Now remember these points when describing a graph
-state the general trend—increases/decreases as **** increases

-give atleast 2 readouts from your graph to support your statement

-one important point is, mention the units. Despite the fact that mark schemes say [ignore units], there are places where they say condone if no units...so better you ALWAYS write the units

-state any points/exceptions that do not fit the general trend

-sometimes...it’s like the curve is divided into two sets...like for the first few readings it decreases less steeply and for the next few..it’s more steeper or vice versa....include this point in your answer, and use data to support your answer....

-If the question mentions ‘with reference to the graph/figure..’ note that u might lose marks if you don’t do so. Read the question carefully..

P.S. This is all based on my understanding, after I did pastpapers, and hope it helps you all..
Remember me in your prayers..
O Allah give us all success in both worlds, Aameen..!!
Click to expand...
Ameeen///
 
angelgirl:)

angelgirl:)

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larina said:
I've got a big confusion about proximal convoluted tubule
Please tell me if i'm correct. This is what I think
-Sodium ions are actively pumped out from the basal membrane of tubule into the blood capillary
-This creates a concentration gradient between the lumen of the tubule and the blood capillary
-Na+ diffuses from the lumen to the capillary(by facilitated diffusion) through a cotransporter that carries glucose as well
-So glucose and Na+ diffuse into the blood capillary and the concentration of ions decrease in the tubule, so water follows by osmosis..


...And this is what mark scheme says...
Na+ actively transported (out of cell) into blood ;
creates concentration gradient ;
Na+ enters cell by diffusion ;
through cotransporter / symporter proteins ;
glucose cotransported / facilitated diffusion (from lumen to cells) ;
glucose diffuses into blood capillaries ;

I dont get what is 'cell' over here, is it the tubule or the blood capillary???
Click to expand...
tubule cell ofcourse...
 
Asha Tabassum

Asha Tabassum

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user said:
angelgirl:) hassam alphabravocharlie

firstly, assalamoalaikum wr wb to u all..

Well you people asked about describing graphs.
Just remember one thing.. ‘describing a graph’ is the best part cuz u just have to tell what the graph shows and u need not worry about why it is so [unless they ask you to explain]...so u get 3-4 marks for free ;) (y)
Now remember these points when describing a graph
-state the general trend—increases/decreases as **** increases

-give atleast 2 readouts from your graph to support your statement

-one important point is, mention the units. Despite the fact that mark schemes say [ignore units], there are places where they say condone if no units...so better you ALWAYS write the units

-state any points/exceptions that do not fit the general trend

-sometimes...it’s like the curve is divided into two sets...like for the first few readings it decreases less steeply and for the next few..it’s more steeper or vice versa....include this point in your answer, and use data to support your answer....

-If the question mentions ‘with reference to the graph/figure..’ note that u might lose marks if you don’t do so. Read the question carefully..

P.S. This is all based on my understanding, after I did pastpapers, and hope it helps you all..
Remember me in your prayers..
O Allah give us all success in both worlds, Aameen..!!
Click to expand...



Thanks ................................. :) Ameen
 
Asha Tabassum

Asha Tabassum

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larina said:
But why does Na+ enters the cell?
Is it this way that when Na+ is diffused into the tubule, the glucose is diffused out into the blood capillary?
Click to expand...

its the mechanism that follows....
first the Na ion will enter into the blood via active transport... this reduces the conc. of Na ion in the tubule cell... so from the fluid of the lumen, through carrier protein Na ion will enter the tubule cell down the conc gradient along with a cotransport molecule eg glucose ... than glucose will b absorbed back into the blood.
 
Asha Tabassum

Asha Tabassum

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Asha Tabassum said:
its the mechanism that follows....
first the Na ion will enter into the blood via active transport... this reduces the conc. of Na ion in the tubule cell... so from the fluid of the lumen, through carrier protein Na ion will enter the tubule cell down the conc gradient along with a cotransport molecule eg glucose ... than glucose will b absorbed back into the blood.
Click to expand...

this is how reabsorption takes place at PCT......
 
angelgirl:)

angelgirl:)

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larina said:
But why does Na+ enters the cell?
Is it this way that when Na+ is diffused into the tubule, the glucose is diffused out into the blood capillary?
Click to expand...
lol u r totally confused...
ok see
1-in the cell of the pct Na+/K+ pumps takes place using ATP prodused from mitocondria...means Na+ out of the cell of pct and into the RBC and K+ pumps inside the cell of pct..
2-so the concentration of Na+ inside the pct decreases..and this comes back to normal when Na+ passively diffuses from the lumen of the pct down its conc.. gradient into the cell of pct acting as co-transporter for glucose,and amio acids...
hope u get it:)
 
Asha Tabassum

Asha Tabassum

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angelgirl:) said:
ya !! so how does it occure...give me some information about it...
Click to expand...


leave abscission

= useful substances are withdrawn from the leaves to the stem.... like pigments for which the colour of the leaves turn green to yellow.... the abscission zone is made up of sepaation layer and protective layer.... the enzyme breaks the cellwall of the separation walls and cause the patiole to b disattached from the stem... the protective layer remain the same bt scar is formed at it..​
 
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