• We need your support!

    We are currently struggling to cover the operational costs of Xtremepapers, as a result we might have to shut this website down. Please donate if we have helped you and help make a difference in other students' lives!
    Click here to Donate Now (View Announcement)

A level Biology: Post your doubts here!

xxfarhaxx

xxfarhaxx

Messages
249
Reaction score
90
Points
38
confused123 said:
you can ask question related to AIDS in that way your chapter revision will be covered as well. still the cambridge endorsed book is the best for study
Click to expand...
wel i do hav a txt buk n da notes in it..bt its nt all clear enough!!!
 
confused_soul

confused_soul

Messages
278
Reaction score
189
Points
53
Hey can any 1 explain me how to measure number of stomatas using microscope
Ders dis question in p5
How do we measure stomatas / mm3
Please explain in detail
 
Saad (سعد)

Saad (سعد)

Messages
224
Reaction score
183
Points
53
As-Salaamu 'Alaykum.

Someone please explain to me the following stuff:

-how sucrose is transported in phloem. Active loading, source, sink, all that stuff... and be simple please. o-o'
-water potential, pressure potential, solute potential... what in the world are these things? o_O how can you deduce what's less negative or more negative or less positive or more positive, etc. I don't understand this at all...

Jazak Allah Khayr.
 
pearl angel

pearl angel

Messages
80
Reaction score
24
Points
18
confused123 said:
you
you can ask question related to immunity in that way your chapter revision will be covered as well. still the Cambridge endorsed book is the best for study
Click to expand...
i cant ask doubts if my concepts aren't clear...i have many problems with immunity chapter...really looking forward to some good notes.
 
confused123

confused123

Messages
576
Reaction score
308
Points
73
Saad (سعد) said:
As-Salaamu 'Alaykum.

Someone please explain to me the following stuff:

-how sucrose is transported in phloem. Active loading, source, sink, all that stuff... and be simple please. o-o'
-water potential, pressure potential, solute potential... what in the world are these things? o_O how can you deduce what's less negative or more negative or less positive or more positive, etc. I don't understand this at all...

Jazak Allah Khayr.
Click to expand...
FROM SOURCE TO CELL C-
consider the companion cell first,where there is active loading of sucrose taking place.
H+ ions are pumped from the companion cells to mesophyll cells containing sucrose by active transport using ATP as an energy source.
As a result the H+ conc builds up in the mesophyll cells generating a potential difference across the membrane.
The H+ ions then move back into the companion cell down a conc. gradient through carrier proteins co-transporting sucrose molecules.
The sucrose molecules then move through the plasmodesmata into the sieve tube element(cell C)

FROM CELL C TO SINK-
When the sugar enters the cell C, due to low water potential being set up water enters by osmosis.
This builds up hydrostatic pressure.
At sink sugar is being used up( for respiration, conversion of sucrose into glucose and fructose)
This creates a pressure gradient between the source and the sink, causing mass flow of solution in phloem sieve tubes from source to sink.
 
R

raamish

Messages
373
Reaction score
33
Points
28
guys are u learning the global distribution of heart disease, and also the global distribution of these diseases. Do any questions come on these in the paper.
 
littlecloud11

littlecloud11

Messages
844
Reaction score
2,495
Points
253
Saad (سعد) said:
As-Salaamu 'Alaykum.

Someone please explain to me the following stuff:

-how sucrose is transported in phloem. Active loading, source, sink, all that stuff... and be simple please. o-o'
-water potential, pressure potential, solute potential... what in the world are these things? o_O how can you deduce what's less negative or more negative or less positive or more positive, etc. I don't understand this at all...

Jazak Allah Khayr.
Click to expand...


Water potential is the tendency of water molecules to move from one region to another. They usually move from a region of high to low water potential. The water potential of pure water is considered to be 0.

Pressure potential can be explained relative to water potential. When you increase the pressure inside a cell, it increases the tendency of the molecules to move out of the cell. An increase in pressure therefore increases the water potential of a solution. the pressure potential is always positive as it increases the water potential.

Solute potential: Adding solute to water lowers it's water potential. As the water potential of pure water is already 0, lowering it will only make it negative. The more solute you add, the more negative the water potential becomes. The amount by which the solute lowers the water potential is called the solute potential.
when you have two solutions, one with more solute (more negative) and one with less solute (less negative), the water will move from the solution with less solute to the one with more solute i.e. less negative to more negative.
A easier way to think is that the water is moving from a less concentrated to more concentrated solution. More solute= more negative=more concentrated. less solute= less negative= less concentrated.

Hope you got this. :p
 
R

raamish

Messages
373
Reaction score
33
Points
28
littlecloud11 said:
Water potential is the tendency of water molecules to move from one region to another. They usually move from a region of high to low water potential. The water potential of pure water is considered to be 0.

Pressure potential can be explained relative to water potential. When you increase the pressure inside a cell, it increases the tendency of the molecules to move out of the cell. An increase in pressure therefore increases the water potential of a solution. the pressure potential is always positive as it increases the water potential.

Solute potential: Adding solute to water lowers it's water potential. As the water potential of pure water is already 0, lowering it will only make it negative. The more solute you add, the more negative the water potential becomes. The amount by which the solute lowers the water potential is called the solute potential.
when you have two solutions, one with more solute (more negative) and one with less solute (less negative), the water will move from the solution with less solute to the one with more solute i.e. less negative to more negative.
A easier way to think is that the water is moving from a less concentrated to more concentrated solution. More solute= more negative=more concentrated. less solute= less negative= less concentrated.

Hope you got this. :p
Click to expand...

guys are u learning the global distribution of heart disease, and also the global distribution of these diseases. Do any questions come on these in the paper.
 
Saad (سعد)

Saad (سعد)

Messages
224
Reaction score
183
Points
53
raamish said:
what is ADP. Is it similiar to ATP??
Click to expand...

Adenosine Diphosphate, yeah its similar to ATP (Adenosine Triphosphate) - only one phosphate is removed. ATP is broken down into ADP and a Phosphate group, which releases the energy stored in the ATP that keeps us alive. The ADP is then built back up into ATP for reuse.
 
littlecloud11

littlecloud11

Messages
844
Reaction score
2,495
Points
253
raamish said:
guys are u learning the global distribution of heart disease, and also the global distribution of these diseases. Do any questions come on these in the paper.
Click to expand...

No, i haven't seen any questions on distribution in any of the past papers. the eradication of diseases like small pox ect. is there but not the distribution.
 
littlecloud11

littlecloud11

Messages
844
Reaction score
2,495
Points
253
Saad (سعد)

Saad (سعد)

Messages
224
Reaction score
183
Points
53
Can someone please tell me what definitions are commonly asked in questions, so that I can prepare them? Jazak Allah.
 
You must log in or register to reply here.
Top