A level Biology: Post your doubts here!

[kareem22010]

can anyone pls pls give any guidance or notes for biology p5 i have my exams on Wednesday.
Thanks in advance

the only thing i do for paper 5 is revise the markscheme( or if you haven't finished all the past papers then you solve as much as you can) and revise the practical content in my coursebook and read examiner reports.

 

[wktang98]

Which xerophytic adaptations reduce the water potential gradient?
1 rolled leaves
2 hairy leaves
3 sunken stomata
4 fewer stomata
5 fleshy leaves

A 1,2,3,4,5 B 1,2 and 3 only C 1, 3 and 4 only D 2 and 5 only

 

[Nisini SIneka]

i don't remember having natural selection questions in paper 42 but the biodiversity questions in this paper were so indirect and tough.

My bad.

 

[Physicsneeded01]

Anybody know where i can get AS topical MCQs for BIO?

 

[saudi789]

O and A Levels Biology tuition offered by Cambridge Qualified Teacher at PIB Colony (near Bahadurabad), Karachi.
Saud Ahmed: 0334-2680886

 

[wolfestein99x]

Which xerophytic adaptations reduce the water potential gradient?
1 rolled leaves
2 hairy leaves
3 sunken stomata
4 fewer stomata
5 fleshy leaves

A 1,2,3,4,5 B 1,2 and 3 only C 1, 3 and 4 only D 2 and 5 only

B ?

 

[nehaoscar]

Here are complete AS and A2 notes for biology 9700!
The notes include each and every point of the syllabus

https://www.xtremepapers.com/community/threads/9700-biology-notes.44871/

Please like and share if you find them helpful
Check out my signature for more A level notes and revision resources!

 

[usef shahin]

would someone mind explaining to me the relationship between solute potential and water potential????

the only 2 similarities/relationship that i can link here is that both have negative values and they CANNOT be positive, however they can also be zero.
the more solute u add the more negative the solute potential becomes and this also causes the water potential to decrease and hence the water potential as well becomes more negative, so they are very related to each other.
remember:
MORE water potential (less solute potential) = LESS negative water potential and solute potential value
LESS water potential (more solute potential) = MORE negative water potential and solute potential value

 

[usef shahin]

When cylinders of potato tissue were immersed in a 0.35 mol dm–3 sucrose solution, they showed
no change in mass.
What will happen when cylinders are immersed in a 0.1 mol dm–3 sucrose solution?
A The pressure potential of the cells will become more positive.
B The solute potential of the cell will become more negative.
C The water potential of the cells will become more negative.
D The water potential of the solution will become less negative

This question requires a bit of a 3 min time to think it
anywho , B is not true cuz the sucrose will diffuse outside the cell due to the concenteration difference AND less solute means less negative not more negative
C is false as well cuz water will move inside the cell due to the potential difference and AGAIN more water means less megative
D is palse(false ) as bell bcz water will move to the cell and leave the poor solution so less water means more negative
IN CONCLUSION we only have A left which is true , now WHY , i cant really explain you unless u did some imaginary math and try to understant it urself the formulate to find the pressure potential is pressure potential = solute potential + water potential , and remember , its ALWAYS positive

 

[usef shahin]

okay, thank you so much
can you help me out and see another little doubt of mine? i just wanted to see if i can check the markscheme pretty well or not.
View attachment 59557 View attachment 59558
my answer:
the antibody has a variable binding region which is complementary to a specific antigen. it is a globular protein with peptide bonds to from a primary structure and hydrogen bonds to form a-helix and b-pleated sheets.

how many points would my answer earn?

A small tip i would like to hand out which is for such questions that relate to binding sites (enzymes questions as well) mention that the shape is SPECIFIC and also say that its COMPLEMENTARY, because sometimes they might reject either specific and accept the term complementary or vice versa , i dont know why they do this but this technique will make sure u get em marks
i hope this will help

 

[usef shahin]

ow, i see. but let's make it 2 marks to be safe( although it might sound inaccurate)
one last doubt for today( the same type of doubt):
Describe the structure of a chloroplast. [9]
My answer: it is a biconvex disc with a diameter of about 7 um. it is surrounded by a double membrane. each chloroplast contains thykaloids, which is arranged into grana and a stroma which contains lipid droplets and ribsomes. the grana contains atp synthase for manufacutre of ATP. the grana is arranged into light harvesting clusters.
View attachment 59560
how many marks should i get for my answer?

i would like to point out that for such large questions try to use better english , atleast better disriptive english grammar and my teacher always said me to link the points with each other (with the super duper moper enlish -.-) its annoying yes but if i showed your answer to my teacher he would give a 3 and i say you deserve a 5 or 4 due to the very poor linking u showed (biology A level is about how u write and how is your english too , writing points like that is not enough at all)

 

[kareem22010]

i would like to point out that for such large questions try to use better english , atleast better disriptive english grammar and my teacher always said me to link the points with each other (with the super duper moper enlish -.-) its annoying yes but if i showed your answer to my teacher he would give a 3 and i say you deserve a 5 or 4 due to the very poor linking u showed (biology A level is about how u write and how is your english too , writing points like that is not enough at all)

somehow, if we are describing the structure here, how is the answer supposed to be made longer when i already wrote the same points as the markscheme?

 

[usef shahin]

somehow, if we are describing the structure here, how is the answer supposed to be made longer when i already wrote the same points as the markscheme?

Here is a sample of how i write my answer :
Chloroplast is a organelle that is found inside plant cells only ,with a diameter of 4-10 micrometer. it has bimembranes , inner and outer membranes from which light passes through, it then has to pass through the stroma which is the cytoplasm of the chloroplast , the stroma consists of 70s ribosomes , the free circular DNA, lipid globules as well as the starch granules, there is also a membranous structure that are known as granum and these are made up of membranes called the thylakoid membranes that contain the photosynthetic pigment hence the light photons enters there and all the reactions go on mostly in that area.

 

[usef shahin]

somehow, if we are describing the structure here, how is the answer supposed to be made longer when i already wrote the same points as the markscheme?

somehow longer than urs but make sure to like something other than the structure only to make the examiner more interested and make the answer more fluid
btw , i dont know how many points i noted there cuz i wrote wat i know not from the markscheme
NOTE : u can add some tiny info from A2 knowledge to impress the examiner but dont go overboard xD

 

[kareem22010]

Here is a sample of how i write my answer :
Chloroplast is a organelle that is found inside plant cells only ,with a diameter of 4-10 micrometer. it has bimembranes , inner and outer membranes from which light passes through, it then has to pass through the stroma which is the cytoplasm of the chloroplast , the stroma consists of 70s ribosomes , the free circular DNA, lipid globules as well as the starch granules, there is also a membranous structure that are known as granum and these are made up of membranes calles thylakoid membranes that contain the photosynthetic pigment hence the light photons enters there and all the reactions go on mostly in that area.

the only thing i see about your answer is that it has more points than mine but there is not much of linking like you are trying to say but to be honest, in this question in particular, i don't think linking between answers is needed. i think linking is needed for questions like "how does ultrafiltration work" etc.

 

[usef shahin]

the only thing i see about your answer is that it has more points than mine but there is not much of linking like you are trying to say but to be honest, in this question in particular, i don't think linking between answers is needed. i think linking is needed for questions like "how does ultrafiltration work" etc.

got em , u r such a genius MaShaaAllah

 

[kareem22010]

got em , u r such a genius MaShaaAllah

thanks , no need to say that, i am not that smart or anything, it's just some careful observation besides i sat biology A2 twice so, i have some experience

 

[drowning-in-studies]

This question requires a bit of a 3 min time to think it
anywho , B is not true cuz the sucrose will diffuse outside the cell due to the concenteration difference AND less solute means less negative not more negative
C is false as well cuz water will move inside the cell due to the potential difference and AGAIN more water means less megative
D is palse(false ) as bell bcz water will move to the cell and leave the poor solution so less water means more negative
IN CONCLUSION we only have A left which is true , now WHY , i cant really explain you unless u did some imaginary math and try to understant it urself the formulate to find the pressure potential is pressure potential = solute potential + water potential , and remember , its ALWAYS positive

Thanks!.... tho posted this a long time ago, im done with my AS

 

[smiling star]

Can someone explain why it's option A and not option B?

 

[smiling star]

Can someone explain why it's option A and not option B?View attachment 61601