A level Biology: Post your doubts here!

[Karim Nabil]

june 8
q.27...C....First of all remove those options which contain PRESENT in lignification of cell wall....now low solute potential means very negative water potential, that's why the water flows into the cells, during loading of sucrose.
Nov 8
Q.4 B.....the magnification is given, so calculate the distance from the air space to rbc...use the formula of magnification, you'll get the answer
Q.31 D...i don't have any explaination for these....just remember that tidal volume is 500 cm3, the vital capacity is 3750 cm3.
june 9
Q.12 D...when lactose is hydrolysed, u get glucose....which can then be used for respiration......
q.14 ..Draw a tangent from 0 to calculate the initial rate of the reaction...
Q 34..A...T cell recognises the graft cells as abnormal cells, and they will destroy them....if you read other options carefully, they don't seem to be orrect...
And there are 2 variants in Nov 09....which one do u want?

dude low solute potential means less solute,hence more water
if not, then be more specific !

 

[sumeru]

dude low solute potential means less solute,hence more water
if not, then be more specific !

Don't get confused because of the words......Low solute potential means more negative.......and more the negative low the water potential..thus, this means that low solute potantial means more solute molecules and hence, lower the water potential...

 

[Snowysangel]

Don't get confused because of the words......Low solute potential means more negative.......and more the negative low the water potential..thus, this means that low solute potantial means more solute molecules and hence, lower the water potential...

No actually low solute potential means less solute molecules. Google it

 

[sumeru]

No actually low solute potential means less solute molecules. Google it

Ahh...you are really confusing me........a highly concentrated solution has lowest solute potential, which means that it has more solute molecules and less water molecules.....that's why concentrated solutions are higly negative...

 

[Snowysangel]

Ahh...you are really confusing me........a highly concentrated solution has lowest solute potential, which means that it has more solute molecules and less water molecules.....that's why concentrated solutions are higly negative...

A high solute potential has a low water potential

 

[sumeru]

A high solute potential has a low water potential

You actually are now making me confused.....high solute means low water potential.....but in terms of potential, pure water will have the highest solute potential......

 

[Snowysangel]

You actually are now making me confused.....high solute means low water potential.....but in terms of potential, pure water will have the highest solute potential......

No who told you that? Pure water has the highest water potential and lowest solute potential

 

[Snowysangel]

You actually are now making me confused.....high solute means low water potential.....but in terms of potential, pure water will have the highest solute potential......

Solute potentials the same as osmotic pressure if that clarifies things

 

[sumeru]

Solute potentials the same as osmotic pressure if that clarifies things

Yes, pure water has high water potential and higher solute potential...which bio book do you use?.....if you use the Cambridge's one, look at it........ln it, it has clearly written that, a solution with more solutes has lower solute potential, and a solution with less solutes has higher solute potential...

 

[mehria]

june 8
q.27...C....First of all remove those options which contain PRESENT in lignification of cell wall....now low solute potential means very negative water potential, that's why the water flows into the cells, during loading of sucrose.
Nov 8
Q.4 B.....the magnification is given, so calculate the distance from the air space to rbc...use the formula of magnification, you'll get the answer
Q.31 D...i don't have any explaination for these....just remember that tidal volume is 500 cm3, the vital capacity is 3750 cm3.
june 9
Q.12 D...when lactose is hydrolysed, u get glucose....which can then be used for respiration......
q.14 ..Draw a tangent from 0 to calculate the initial rate of the reaction...
Q 34..A...T cell recognises the graft cells as abnormal cells, and they will destroy them....if you read other options carefully, they don't seem to be orrect...
And there are 2 variants in Nov 09....which one do u want?

solute potential is represented by -ve sign.. the more negative a solution is, the more concentrated it will be...i.e. solute potential will b more...
dnt cnfuse urself by readng the textbook... still if u have any doubt then look at this question...it clearly says that less negative means high water potential n less solute potential

 

[@yesha]

your're welcome. Well, solve a full year papers theory like May/June - Oct/Nov 2013 with the help of marking scheme. underline those questions which you don't understand because there are few students who are great at theory but their question COMPREHENSION is weak. Try to understand what the examiner wants. When you've done with it, solve the rest of the papers.
I hope it will be helpful! Please pray for me as well.

Thank u soo much
I'll pray for ur success ^_^

 

[@yesha]

Anyone tell me how to calculate magnification ?

 

[asma tareen]

Anyone tell me how to calculate magnification ?

Image size/actual size

 

[@yesha]

Okay thanks

 

[joanna omar]

june 8
q.27...C....First of all remove those options which contain PRESENT in lignification of cell wall....now low solute potential means very negative water potential, that's why the water flows into the cells, during loading of sucrose.
Nov 8
Q.4 B.....the magnification is given, so calculate the distance from the air space to rbc...use the formula of magnification, you'll get the answer
Q.31 D...i don't have any explaination for these....just remember that tidal volume is 500 cm3, the vital capacity is 3750 cm3.
june 9
Q.12 D...when lactose is hydrolysed, u get glucose....which can then be used for respiration......
q.14 ..Draw a tangent from 0 to calculate the initial rate of the reaction...
Q 34..A...T cell recognises the graft cells as abnormal cells, and they will destroy them....if you read other options carefully, they don't seem to be orrect...
And there are 2 variants in Nov 09....which one do u want?

THANKS ALOT !!
Nov 2009 v1

 

[joanna omar]

June 08 Q 27:_ Phloem tubes are not lignified and solute potential of companion cells are more than sieve tube cells.
Nov 08 Q4:_ check the attachement

Thankss aloot for that attachment and the it is more clear (great idea girl)

 

[joanna omar]

solute potential is represented by -ve sign.. the more negative a solution is, the more concentrated it will be...i.e. solute potential will b more...
dnt cnfuse urself by readng the textbook... still if u have any doubt then look at this question...it clearly says that less negative means high water potential n less solute potential

Guysss this is true low solute potential means ,less -ve water potential so water potential high

And in june 08 Q27 .......Isnt the solute.P suppose to be high dude to presence of sucrose ?

 

[mehria]

Guysss this is true low solute potential means ,less -ve water potential so water potential high

And in june 08 Q27 .......Isnt the solute.P suppose to be high dude to presence of sucrose ?

but i think most of sucrose is converted to starch in phloem sieve tube cells...that is then unloaded to the sink/storage organs

 

[joanna omar]

but i think most of sucrose is converted to starch in phloem sieve tube cells...that is then unloaded to the sink/storage organs

okay but stillf precence of sucrose makes solute potential high in phloem ?
AM I right ?

 

[mehria]

okay but stillf precence of sucrose makes solute potential high in phloem ?
AM I right ?

yes