Biology/Physics ATP Preparation Thread

[intelnehalem]

You are given a solution of starch,pepsin and glucose in three different unlabelled test-tubes. Carry out a detailed experiment to show which test tube contains which sample. Include any safety precautions that you might need.

 

[izzahzainab]

Anyone?

Last part of this paper... Draw on the FIGURE and post the image back...PAPER

i cant write on image but in 1st it will be rectangle... n 2nd it will be an inverted triangle

here is another option. this one is an eraser, with two small pieces of strings carrying a balanced wight (two small erasers)

 

[CaptainDanger]

Izzah Zainab I don't get what you exactly mean ?

 

[sksuriza]

me neither

 

[sksuriza]

You are given a solution of starch,pepsin and glucose in three different unlabelled test-tubes. Carry out a detailed experiment to show which test tube contains which sample. Include any safety precautions that you might need.

1st divide the contents of each testtube into 3 tubes to carry out three kinds of foood test
and make 3 set of experimental testubes

1st obtain 3 testtubes each wd different contents and test it wd iodine solution.... the one tht turns blue black wd iodine contains starch....

now get the other sample set
add 2cm cube of benedict solution and heat in a water bath.. the tube tht will give red-brown ppt wd it will contain glucose a reducing sugar...

now the final pepsin is an enzyme tht digest protein.....
so add 2cm cube of HCl to the last set and any protein ie 2cm cube egg albumen.... give it a temp of 35-40 degree and leave it for 3-6 hours... now test all 3 tubes with biuret solution... the one tht fails to give a violet ppt contains pepsin

 

[sksuriza]

in the 3rd test it fails to give violet cuz pepsin has digested protein

 

[intelnehalem]

You are given a solution of starch,pepsin and glucose in three different unlabelled test-tubes. Carry out a detailed experiment to show which test tube contains which sample. Include any safety precautions that you might need.

Take a small, equally sized sample from each test-tube into a white tile and add equal amounts of iodine solution (you have to do this once for each sample until you find the starch solution). The solution of starch will show a color change of Iodine from Red-brown to Blue-black. You have now identified the Starch solution! Isolate it and label it adequately.
Now,
you can either perform the Biuret test to prove the presence of Pepsin (enzymes are proteins) or you can do the benedict's test to prove the presence of glucose.
1.Biuret test-
Take a small equally sized sample from the remaining 2 test tubes into 2 separate test tubes, add 2cm3 of Sodium Hydroxide solution to each sample. Add a few drops of copper sulphate solution into each sample. The sample which shows a color change of blue to mauve/violet/lilac is Pepsin since pepsin is an enzyme and enzymes are proteins.
Label the test-tube and since only one other test tube remains, it has to be glucose

2. Benedict's test:
Take equal volumes of each sample into a separate BOILING TUBE , add equal volumes of Benedicts solution and heat over a water bath. The test tube which shows a colour change of Blue to brick rep (ppt) obviously contains a reducing sugar which is glucose. Label this appropriately and since there is only 1 more test tube remaining it has to be pepsin !

Precautions:
Use gloves/lab coat when handling Sodium Hydroxide and other substances
Use of a water bath

 

[intelnehalem]

You are given a solution of starch,pepsin and glucose in three different unlabelled test-tubes. Carry out a detailed experiment to show which test tube contains which sample. Include any safety precautions that you might need.

1st divide the contents of each testtube into 3 tubes to carry out three kinds of foood test
and make 3 set of experimental testubes

1st obtain 3 testtubes each wd different contents and test it wd iodine solution.... the one tht turns blue black wd iodine contains starch....

now get the other sample set
add 2cm cube of benedict solution and heat in a water bath.. the tube tht will give red-brown ppt wd it will contain glucose a reducing sugar...

now the final pepsin is an enzyme tht digest protein.....
so add 2cm cube of HCl to the last set and any protein ie 2cm cube egg albumen.... give it a temp of 35-40 degree and leave it for 3-6 hours... now test all 3 tubes with biuret solution... the one tht fails to give a violet ppt contains pepsin

This is correct but there is a much easier method I have just posted that

 

[Silent Hunter]

This is answer to the physics 2010 paper last question last part...........hope its correct

 

[Silent Hunter]

DONT KNOW WHATS the problem .......... acnt upload the photo only

 

[intelnehalem]

This is answer to the physics 2010 paper last question last part...........hope its correct

Yes

 

[Silent Hunter]

 

[VelaneDeBeaute]

sksuriza u wrote
now the final pepsin is an enzyme tht digest protein.....
so add 2cm cube of HCl to the last set and any protein ie 2cm cube egg albumen.... give it a temp of 35-40 degree and leave it for 3-6 hours... now test all 3 tubes with biuret solution... the one tht fails to give a violet ppt contains pepsin

while intelnehalem wrote
Take a small equally sized sample from the remaining 2 test tubes into 2 separate test tubes, add 2cm3 of Sodium Hydroxide solution to each sample. Add a few drops of copper sulphate solution into each sample. The sample which shows a color change of blue to mauve/violet/lilac is Pepsin since pepsin is an enzyme and enzymes are proteins.

Clearly, im confused wid which 2 go...perhaps im confused...o yeah.i am...!! Now explain, wudnt u 2..??!! :%)

 

[intelnehalem]

sksuriza u wrote
now the final pepsin is an enzyme tht digest protein.....
so add 2cm cube of HCl to the last set and any protein ie 2cm cube egg albumen.... give it a temp of 35-40 degree and leave it for 3-6 hours... now test all 3 tubes with biuret solution... the one tht fails to give a violet ppt contains pepsin

while intelnehalem wrote
Take a small equally sized sample from the remaining 2 test tubes into 2 separate test tubes, add 2cm3 of Sodium Hydroxide solution to each sample. Add a few drops of copper sulphate solution into each sample. The sample which shows a color change of blue to mauve/violet/lilac is Pepsin since pepsin is an enzyme and enzymes are proteins.

Clearly, im confused wid which 2 go...perhaps im confused...o yeah.i am...!! Now explain, wudnt u 2..??!! :%)

sksuriza probably forgot that pepsin is infact a protein that is why he took that approach. I directly tested for the protein (pepsin) while he took a long way to prove this

 

[CaptainDanger]

DONT KNOW WHATS the problem .......... acnt upload the photo only

That's okay... Thanks....

 

[RockStar15]

Nice work guys!!!
But plz concentrate on physics ATP after Bio...

 

[KarachiRocker]

RockStar, post some questions here and we will try to answer them, for practice

 

[RockStar15]

KarachiRocker thx buddy, I just wanted to revise important topics so that nothing is left...

 

[sksuriza]

hey intel ... i ws jxy confused whch one to do so i decided to do a detailed test...
well both ways we will get full marks rite/????

n if i m wrong do tell my mistakes i learn 4rm thm..
so whole revision done???
R there any more qs

 

[Muhammad Talha]

Hey plz help me Q3 of this ppr....http://www.xtremepapers.me/CIE/Cambridge O Levels/5090 - Biology/5090_s09_qp_6.pdf