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Biology; Chemistry; Physics: Post your doubts here!

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Awesome12

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Laibaaa said:
Okay this is probably a stupid question but this has been bothering me since day1.

When testing for importance of chlorophyll in a leaf,
we first remove chlorophyll from the leaf by putting it in ethanol. This means that the leaf doesn't have chlorophyll and can not photosynthesise.
Then no starch should be there right? But when we test with iodine, it says blueblack colour :/
Do check this question;

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Biology (5090)/5090_s08_qp_6.pdf
On pg8, Q2) .
Click to expand...
Consider there is an animal A. It has died. Now since it has died, it cannot feed neither produce energy. But decomposers still feed on it. How? It already has a reserve of food in it. Like this plants already have a reserve of starch and cannot photosynthesize when we de-chlorophyll it
 
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Fate0

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Laibaaa said:
Okay this is probably a stupid question but this has been bothering me since day1.

When testing for importance of chlorophyll in a leaf,
we first remove chlorophyll from the leaf by putting it in ethanol. This means that the leaf doesn't have chlorophyll and can not photosynthesise.
Then no starch should be there right? But when we test with iodine, it says blueblack colour :/
Do check this question;

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Biology (5090)/5090_s08_qp_6.pdf
On pg8, Q2) .
Click to expand...

We removed the chlorophyll AFTER the photosynthesis had taken place. :p
 
ciesgetoveralready

ciesgetoveralready

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Laibaaa said:
Okay this is probably a stupid question but this has been bothering me since day1.

When testing for importance of chlorophyll in a leaf,
we first remove chlorophyll from the leaf by putting it in ethanol. This means that the leaf doesn't have chlorophyll and can not photosynthesise.
Then no starch should be there right? But when we test with iodine, it says blueblack colour :/
Do check this question;

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Biology (5090)/5090_s08_qp_6.pdf
On pg8, Q2) .
Click to expand...
It means that the leaf can not photosynthesise further. But since before the treatment , photosynthesis was occuring in the plant so starch will be present!
 
Mahnoorfatima

Mahnoorfatima

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What is the difference between accuracy and reliability of teh result. In the examiner report they say students who mentioned that taking three counts will increase accuracy than reliability. Why is it wrong? o_O
 
kirann

kirann

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Fate0 said:
Eliminate the answers.
It cant be (a) because if X was more reactive than Cu and Mg then it should also displace Zn. But they have said that the deposit is in 2 tubes only.
It cant be (c) because if X was more reactive than Na and Mg then it should displace Zn and Cu aswell.
It cant be (d) because if X was more reactive than Mg then it should also displace Cu.

(b) is the correct answer because if X is after Na and Mg in reactivity series but before Cu and Zinc it will only displace those two.
Click to expand...
got it :D didnt know i need to look in reactivity series for this question :p
 
ciesgetoveralready

ciesgetoveralready

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Mahnoorfatima said:
What is the difference between accuracy and reliability of teh result. In the examiner report they say students who mentioned that taking three counts will increase accuracy than reliability. Why is it wrong? o_O
Click to expand...
First you will get to know that the result is accurate. Then you can rely on it "yes its correct and I can use it for further investiagtions!"
 
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Fate0

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Accuracy is the precision of the experiment; how precise it is.
Reliability is how right/correct the experiment is?

For example if the students conduct the experiment in a wrong manner, their answer is not reliable (it cannot be counted upon for investigation) but they can still improve it's accuracy.
 
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Fate0

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kirann said:
at what temp amylase breakdown starch? 35-37?
Click to expand...

There is no specific temperature.
It will breakdown starch at any temp but the rate will be different.
Yes you can say that at 35 it will break maximum starch as it is most reactive at this optimum temperature.
 
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