A2 Biology | Post your doubts here

[smartangel]

can someone please explain the hill reaction?

 

[angelgirl:)]

can someone please explain the hill reaction?

The Hill reaction is formally defined as the photoreduction of an electron acceptor by the hydrogens of water, with the evolution of oxygen. In vivo, or in the organism the final electron acceptor is NADP+. We can measure the rate of the Hill reaction in isolated chloroplasts. This procedure uses a dye as an artificial electron acceptor that changes color as it is reduced. DCIP (2,6-dichlorophenolindophenol) is a dye which is blue in its oxidized form and colorless in its reduced form.

 

[smartangel]

how are you guys preparing for p5??

 

[hm12]

how are you guys preparing for p5??

exactly i am so scared of p5 i am still not satisfied after doing all the past papers

 

[MysteRyGiRl]

exactly i am so scared of p5 i am still not satisfied after doing all the past papers

me tooo

 

[MysteRyGiRl]

can smbdy explain da use of a respiratory inhibitor??

 

[MysteRyGiRl]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s09_qp_5.pdf
one more ques.
for Q no 2,why arent snails an independant variable? i mean we cant control da predation by birds right??

 

[angelgirl:)]

exactly i am so scared of p5 i am still not satisfied after doing all the past papers

solved all the papers...still not satisfied????

 

[hm12]

solved all the papers...still not satisfied????

didnt exactly solve them just read the question made up an answer in mind and read the marking schemes to check if my ideas were correct.....the thing is i dont come up with the required number of points to get full marks:/

 

[angelgirl:)]

can smbdy explain da use of a respiratory inhibitor??

respiratory chain inhibitors affect the production of ATP by uncoupling the process of ATP production that is linked to the respiratory event, i.e., stops oxidative phosphorylation . The active transport of sugars uses ATP as part of a sodium /K ATPase pump.Without the ATP being supplied this active transporter will NOT work..thus one would expect that if aborption of sugars were strongly dependent on an ATP based system then the use of a respiratory inhibitor would significantly reduce the rate of absorption for those sugars .

 

[angelgirl:)]

didnt exactly solve them just read the question made up an answer in mind and read the marking schemes to check if my ideas were correct.....the thing is i dont come up with the required number of points to get full marks:/

its simple..u just have to divide the 8 marks for 6 points...just say
1----the independent variable..how its controlled
2----dependent variable...how its controlled and standardised
3----the variables that have to be kept constant
4----little procedure is needed for some Qs
5----safty precautions
6----how to make it more accurate and reliable
if u answer this much correctly 6 to 7 marks for sure u will gain...

 

[user]

its simple..u just have to divide the 8 marks for five points...just say
1----the independent variable..how its controlled
2----dependent variable...how its controlled and standardised
3----the variables that have to be kept constant
4----little procedure is needed for some Qs
5----safty precautions
5----how to make it more accurate and reliable
if u answer this much correctly 6 to 7 marks for sure u will gain...

AsSalamoAlaikum wr wb!

That's exactly what I do...I mean what I understood when I once did pastpapers...!!

 

[user]

its simple..u just have to divide the 8 marks for five points...just say
1----the independent variable..how its controlled
2----dependent variable...how its controlled and standardised
3----the variables that have to be kept constant
4----little procedure is needed for some Qs
5----safty precautions
5----how to make it more accurate and reliable
if u answer this much correctly 6 to 7 marks for sure u will gain...

to add...
for accuracy...=> always some better apparatus...

for reliability => like if u have concentration as independent vaariable, say, take atleast 5 different concentrations....and with each ....repeat at least "three times" [yup not less than that, or u wont get the mark..] , take average, and plot..

 

[angelgirl:)]

AsSalamoAlaikum wr wb!

That's exactly what I do...I mean what I understood when I once did pastpapers...!!

w/s wr wb...
i know i just solved hardly 3 to 4 papers and i understood this much is needed for the first Q...
2nd Q is different every year..its like kind of research you have to do...but u should be familiar with those x^2, t.test. standerd deviation.standered error,signeficant and non signeficant meanings etc...

 

[angelgirl:)]

to add...
for accuracy...=> always some better apparatus...

for reliability => like if u have concentration as independent vaariable, say, take atleast 5 different concentrations....and with each ....repeat at least "three times" [yup not less than that, or u wont get the mark..] , take average, and plot..

yes exactly...thats how to make it accurate and reliable..

 

[hm12]

its simple..u just have to divide the 8 marks for 6 points...just say
1----the independent variable..how its controlled
2----dependent variable...how its controlled and standardised
3----the variables that have to be kept constant
4----little procedure is needed for some Qs
5----safty precautions
6----how to make it more accurate and reliable
if u answer this much correctly 6 to 7 marks for sure u will gain...

i know this i learnt it from the past papers i was talking about some random 2-3 marks parts of the questions which come up sometimes anyways i hope we all do really well in p5 and come up with a good result Ameen!

 

[angelgirl:)]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s09_qp_5.pdf
one more ques.
for Q no 2,why arent snails an independant variable? i mean we cant control da predation by birds right??

equal no. of banded and unbanded snails were released into both areas...means 1 area without bird and the other area with birds living there...so investigating the presence and absence of birds on the no. of snails...of course it will be the independent variable...

 

[angelgirl:)]

i know this i learnt it from the past papers i was talking about some random 2-3 marks parts of the questions which come up sometimes anyways i hope we all do really well in p5 and come up with a good result Ameen!

InshaAllah...

 

[hassam]

http://www.xtremepapers.com/papers/...nd AS Level/Biology (9700)/9700_w09_qp_51.pdf
question 2 d......we have 10 samples each fot Y and no Y ....and again ms says insufficient replicates???
and one rule for paper 5.........use the rounded up value obtained too calculate subsequent ansers...........bloody examiners give an ecf for calculator values carried forward

 

[hassam]

http://www.xtremepapers.com/papers/...nd AS Level/Biology (9700)/9700_w09_qp_52.pdf
3 b (ii)
there are 5 repeats at each temp. and conc.................still insufficient data??????