A level Biology: Post your doubts here!

[joanna omar]

Does methylene blue stain the DNA/chromosomes if mitosis is to be observed under a microscope?

Yeah ..I guess but better ethidum bromide

 

[DeViL gURl B)]

Because at the beginning of a reaction, there shouldn't be any free active sites because many substrate molecules are present, instead more E-S complex forming so answer is B

Thank u
And can u give a reason y isn't it C? Please

 

[anamta]

What is the logic behind this question?.--->Q14 http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s13_qp_12.pdf

the NUMBER OF BUBBLES can never be in decimals even if its the mean.... because there cant be 9.2 or 16.2 or 18.8 bubbles

 

[EmiraS]

q4? http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s13_qp_11.pdf

 

[Karim Nabil]

Thank u
And can u give a reason y isn't it C? Please

Because at the beginning of the reaction, there are many substrate molecules to bind to the active site, inhibition is reversible(temporary). So many E-S complex is formed.

 

[DeViL gURl B)]

http://papers.xtremepapers.com/CIE/...nd AS Level/Biology (9700)/9700_w10_qp_13.pdf

Question 38 and 40 please anyone??!!!

 

[MiniSacBall]

http://papers.xtremepapers.com/CIE/...nd AS Level/Biology (9700)/9700_s11_qp_11.pdf

Q14, when a non-competitive inhabitor acts it does changes the shape of active site doesn't it

 

[DeViL gURl B)]

Yes

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s11_qp_11.pdf

Q14, when a non-competitive inhabitor acts it does changes the shape of active site doesn't it

 

[DeViL gURl B)]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_w10_qp_13.pdf

Question 38 and 40 please anyone??!!!

Anyyyyoneeee??? :/:/:/

 

[MiniSacBall]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_w10_qp_13.pdf

Question 38 and 40 please anyone??!!!

Not sure about 39 but in question 40, they are asking about the total energy?
So you need to multiply all those values to get the total energy of each type organism, living in the area!
When you multiply all of them you will find your answer which is B
Hope you have got it!

And for my doubt, markscheme says that it doesn't. WHY ?

 

[DeViL gURl B)]

Not sure about 39 but in question 40, they are asking about the total energy?
So you need to multiply all those values to get the total energy of each type organism, living in the area!
When you multiply all of them you will find your answer which is B
Hope you have got it!

And for my doubt, markscheme says that it doesn't. WHY ?

Thank youu
Ohh well that question even confused me.. So I memorized it is the answer C?
Btw don't u think that when they said binds to an ES complex..there are many active sites on an enzyme not only one plus if it's a non competitive inhibitor then ... The reaction rate is reduced ...
I'm sorry but even I got confused....

 

[joanna omar]

State a reason why t-test used ?

and

State a reason why chi-sq test used ?

 

[MÁťT PŭמҚ]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_w11_qp_53.pdf

somebody plz solve Q2 from this and tell me how they have calculated the expected ratios...!!

do the cross for the data given in cross 1 and then find out the ratio of offspring and then multiply it with the total observed number!
cross 1 without tail x without tail
will give 3 without tail offspring and 1 with tail
so the ratio of offspring is 3:1
and now for offspring with tail 1/4 multiply with the total observed number that is 112 1/4 x 112 = 28
and without tail 3/4 x 112 = 84

 

[MÁťT PŭמҚ]

State a reason why t-test used ?

and

State a reason why chi-sq test used ?

t-test is used bcoz data is continuous and chi-sq bcoz data is discontinuous!

 

[Shada Mohammed]

http://papers.xtremepapers.com/CIE/...nd AS Level/Biology (9700)/9700_s13_qp_13.pdf
Q19 ,23, 34,39

 

[joanna omar]

t-test is used bcoz data is continuous and chi-sq bcoz data is discontinuous!

but how in m.s they say both are discrete ?

 

[DeViL gURl B)]

http://papers.xtremepapers.com/CIE/...nd AS Level/Biology (9700)/9700_w12_qp_12.pdf

Question 34 please!!!!!!

 

[MÁťT PŭמҚ]

but how in m.s they say both are discrete ?

t-test is not discrete!

 

[ZaqZainab]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_w12_qp_12.pdf

Question 34 please!!!!!!

Arteries blood leave heart so the oxygenated blood in it too
Veins blood enters the heart so the oxygenated blood it too
Oxygen in 5 dm^3 of blood in arteries is 950 (using ratio 100:19)
Oxygen in 5dm^3 of blood in the veins is 625 (using ratio 100:12.5)
Total uptake the used oxygen by heart = 950-625=325

 

[DeViL gURl B)]

Arteries blood leave heart so the oxygenated blood in it too
Veins blood enters the heart so the oxygenated blood it too
Oxygen in 5 dm^3 of blood in arteries is 950 (using ratio 100:19)
Oxygen in 5dm^3 of blood in the veins is 625 (using ratio 100:12.5)
Total uptake the used oxygen by heart = 950-625=325

Thank u
But ... How do u get the ratio?