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Biology 33, how was it?

How was it?

  • Easy

    Votes: 6 26.1%

  • Normal.

    Votes: 10 43.5%

  • Difficult

    Votes: 7 30.4%
  • Total voters
    23
I

Irfan1995

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xtremeforums: looking at mark schemes, they normally provide a range of values which are acceptable. However, if they required a very accurate answer, yours would be correct.
 
xtremeforums

xtremeforums

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Irfan1995 said:
xtremeforums: looking at mark schemes, they normally provide a range of values which are acceptable. However, if they required a very accurate answer, yours would be correct.
Click to expand...
What did you write for this question...How could you modify the experiment to find out the activity of enzymes at different temperatures?
 
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♥Яαηõõşḧ♥

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xtremeforums said:
What did you write for this question...How could you modify the experiment to find out the activity of enzymes at different temperatures?
Click to expand...
prepare 4 water baths ( 20, 40,60,80) using cold water ,hot water and a thermometer. Label four large test tubes accordinlgy and put 10 seeds of the same size in each test tube. and add to them 3 cc of sucrose solution. leave in the approriate water bath for 20 mins.. then extract 2cc of each solution and add to it 2cc of Benedicts. put in a boiling water bath and observe the first color change.... the least time taken for the color to change would mean the highest enzyme activity ( which would probably be at 40 degrees)
i wrote smth like that
 
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♥Яαηõõşḧ♥ said:
prepare 4 water baths ( 20, 40,60,80) using cold water ,hot water and a thermometer. Label four large test tubes accordinlgy and put 10 seeds of the same size in each test tube. and add to them 3 cc of sucrose solution. leave in the approriate water bath for 20 mins.. then extract 2cc of each solution and add to it 2cc of Benedicts. put in a boiling water bath and observe the first color change.... the least time taken for the color to change would mean the highest enzyme activity ( which would probably be at 40 degrees)
i wrote smth like that
Click to expand...
me too, and at the end i wrote, plot a graph of time taken for initial colour change against temp..
 
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Irfan1995

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Then both of you should receive full credit, although honestly, you didn't have to write all that. They asked for modifications of the original experiment, so you only have to write what did you change. But don't worry, you'll still get all the marks :)
 
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Irfan1995

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Umm, let's see:
Benedict's solution was supposed to be kept anywhere between 80 and 100 degrees (anything written in between would be acceptable)
You're supposed to take 2 cm3 from each solution and 2cm3 (or more) from benedict's
Table:
Headings: concentrations of R, volume of solution, volume of water
0.4---10---0.0
0.3---7.5---2.5
0.2---5.0---5.0
o.1---2.5---7.5
0.0---0.0---10

Describing trend of change in pH for leaves: sharply increases until pH of 5.3 then sharply decreases (although decrease is less steep than increase)
Explaining trend in activity between pH between 5.3 and 6.4: the relatively higher concentrations of OH- ions could interact with the protein structure (by forming hydrogen bonds with the polypeptides) and denature the enzymes. So activity decreases.

And I think that's all. Good luck to everyone on paper 1 this Monday. How are you guys preparing? I've killed the book already (more than 10 times) studying for paper 2, and right now I'm solving all past papers from 2007 - 2012, starting from the most recent. I'll try to be on the paper 1 thread as much as possible :)
 
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Irfan1995 said:
Umm, let's see:
Benedict's solution was supposed to be kept anywhere between 80 and 100 degrees (anything written in between would be acceptable)
You're supposed to take 2 cm3 from each solution and 2cm3 (or more) from benedict's
Table:
Headings: concentrations of R, volume of solution, volume of water
0.4---10---0.0
0.3---7.5---2.5
0.2---5.0---5.0
o.1---2.5---7.5
0.0---0.0---10

Describing trend of change in pH for leaves: sharply increases until pH of 5.3 then sharply decreases (although decrease is less steep than increase)
Explaining trend in activity between pH between 5.3 and 6.4: the relatively higher concentrations of OH- ions could interact with the protein structure (by forming hydrogen bonds with the polypeptides) and denature the enzymes. So activity decreases.

And I think that's all. Good luck to everyone on paper 1 this Monday. How are you guys preparing? I've killed the book already (more than 10 times) studying for paper 2, and right now I'm solving all past papers from 2007 - 2012, starting from the most recent. I'll try to be on the paper 1 thread as much as possible :)
Click to expand...
same here but i haven't rlly killed the book as many times as u :p mashallah
what abt the older years ( 2002-2006) are u gonna solve them??
and do u think its important that we finish the syllabus for p1 or do u think pps are enough??
 
Nishii

Nishii

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xtremeforums said:
On the x axis, pH... And on the y axis, Activity of enzyme...
and we were suppose to make two line graphs, and label each one clearly, eg. leaves or bark.

Did anyone else do this?
Click to expand...
me! but i joined the points by lines, i did not make a curve!
 
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Irfan1995

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The syllabus changed completely at 2007, so they're getting different questions starting May/June '07.
I'd recommend doing both past papers and studying the syllabus. If you don't have time to do both, then I would prefer if you study the syllabus rather than solving past papers. If you really have no time for that, then you'll have to read notes. Then just solve one or two past papers just so you could know what they could type of questions they could throw at you. Good luck :)
 
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♥Яαηõõşḧ♥ said:
same here but i haven't rlly killed the book as many times as u :p mashallah
what abt the older years ( 2002-2006) are u gonna solve them??
and do u think its important that we finish the syllabus for p1 or do u think pps are enough??
Click to expand...
That depends on whether u have ur concepts clear or not...
Revise the syllabus again if u have any doubts..

I personally think pastpapers are more important at this stage!
and im going to solve all pastpapapers... 2002-2012 inshAllah... In case they repeat a question.
 
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Irfan1995

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You're supposed to join the points by two lines (one going up and the other going down). I also made the line slightly curved near the top as I think the graph should be differentiable at all points (so no sharp corners).
 
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♥Яαηõõşḧ♥

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Irfan1995 said:
The syllabus changed completely at 2007, so they're getting different questions starting May/June '07.
I'd recommend doing both past papers and studying the syllabus. If you don't have time to do both, then I would prefer if you study the syllabus rather than solving past papers. If you really have no time for that, then you'll have to read notes. Then just solve one or two past papers just so you could know what they could type of questions they could throw at you. Good luck :)
Click to expand...
ok,, thanks for the advice
good luck to u too :)
 
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