Biology; Chemistry; Physics: Post your doubts here!

[Fallen316]

please explain q3 of http://www.xtremepapers.com/papers/...onal O Level/Biology (5090)/5090_s03_qp_1.pdf

 

[SALT]

it increases the rate maybe because it increases the movement of molecules.
Correct me if i'm wrong

its boiled and cooled and then placed in distilled water
so...how does it effect??

 

[Talhakhan]

What are nitrifying and de-nitrifying bacteria????? Plz help needed...

 

[SALT]

please explain q3 of http://www.xtremepapers.com/papers/...onal O Level/Biology (5090)/5090_s03_qp_1.pdf

its 0.5 mol cos tht is the conc where the change in length is constant

 

[Fallen316]

its 0.5 mol cos tht is the conc where the change in length is constant

thats my answer too but e.r says its 0.3 mol

 

[Talhakhan]

What are nitrifying and de-nitrifying bacteria????? Plz help needed...

 

[SALT]

thats my answer too but e.r says its 0.3 mol

oh my bad!
the y axis says PERCENT change in length....0.3mol is the point where it graph cuts the x axis(ie. the point where theres no change in length) so the conc of cell nd solution is the sameat dis point

 

[UziB]

thats my answer too but e.r says its 0.3 mol

It will be 0.3 mol as the percentage change in length of the potato at that time is ZERO according to the graph's corresponding value. That means the water potential in the potato and outside the potato is equal so no water is moving in or out of the potato, hence the potato will not increase or decrease in mass. This one was a little confusing but hope you got the concept

 

[Fallen316]

What are nitrifying and de-nitrifying bacteria????? Plz help needed...

- nitrifying bacteria convert ammonium ions first into nitrites then into nitrates

- denitrifying bacteria breaks down the nitrogen turning it back into N2 gas.​

 

[SALT]

Fallen316....
actually my question was the question 3 from the paper:
http://www.xtremepapers.com/papers/...nal O Level/Biology (5090)/5090_w10_qp_11.pdf

 

[Fallen316]

Fallen316....
actually my question was the question 3 from the paper:
http://www.xtremepapers.com/papers/CIE/Cambridge International O Level/Biology (5090)/5090_w10_qp_11.pdf

Boiling will damage the membrane proteins, so they are no longer partially permeable. The unboiled tissue will allow osmosis, so the distilled water will enter, swelling the cells.

 

[Talhakhan]

- nitrifying bacteria convert ammonium ions first into nitrites then into nitrates

- denitrifying bacteria breaks down the nitrogen turning it back into N2 gas.​

Thanks for the help buddy......

 

[SALT]

Boiling will damage the membrane proteins, so they are no longer partially permeable. The unboiled tissue will allow osmosis, so the distilled water will enter, swelling the cells.

copied nd pasted the examiner's report, huh?

 

[Fallen316]

Thanks for the help buddy......

you're welcome

copied nd pasted the examiner's report, huh?

you got the concept, didn't you ?

 

[SALT]

you got the concept, didn't you ? ​

not really...
plz explain

 

[snoonono]

lol hope it falls

 

[snoonono]

please explain q3 of http://www.xtremepapers.com/papers/CIE/Cambridge International O Level/Biology (5090)/5090_s03_qp_1.pdf

answer is C bcz rate of osmosis in equals out, so no change in length, so u look on u axis for zero, and check the conc, which will be 0.3(C)

 

[Talhakhan]

Guys need help is it necessary to do yearly past papers ....
P.S i have done all topical 1998-09 ......

 

[Spidey21]

how does boiling a sample of potato affect the rate of osmosis?? nd why?
just the general concept...

it makes the membrane more permeable

 

[Spidey21]

please explain q3 of http://www.xtremepapers.com/papers/CIE/Cambridge International O Level/Biology (5090)/5090_s03_qp_1.pdf

it has to be C cuz thats when there is not change in the size of the strip moreover i had done this in my pps and the answer there was 0.5 but it was WRONG!!