A level Biology: Post your doubts here!

[joanna omar]

HELP !
Nov 2013 v1/3

Q1 , 7 , 8 and 17 ?

 

[DeViL gURl B)]

http://papers.xtremepapers.com/CIE/...nd AS Level/Biology (9700)/9700_s13_qp_12.pdf

Question no. 22 ??
What is the difference btw base pairs and nucleotides??

 

[Busy Buddy]

22) A length of double-stranded DNA contains 120 nucleotides and codes for polypeptide X.
What is the maximum length of polypeptide X?
A. 20 amino acids
B. 40 amino acids
C. 60 amino acids
D. 120 amino acids

correct answer : A

My doubt : how is it A?

Source : 2012 may - june paper_11

 

[Snowysangel]

They bind to the mast cells for triggering them to release histamine and cause inflammation. Then an immune response is stimulated, attracting nearby neutrophils to the antigen.the neutrophil recognize and then attach to the antigen, engulf it by phagocytosis, then it is digested and released out of neutrophil by exocytosis, it can also act as antigen presenting cell, then if the antigen is in body-cells, cell mediated response stimulated(t-cells), but if outside cells in tissue fluid then humoral response stimulated(b-cells)
T-cells with complementary receptors to the antigen is activated then and divide by mitosis, then action is taken depending on its type.
In b-cells, those with specific antibody receptors are only selected(clonal selection), then they divide differentiating into plasma cells (that secrete antibodies) and memory cells.
Only alveolus, alveolar duct is involved in gaseous exchange.

But you just said that the bronchus is involved in gaseous exchange...that's why they're inner membrane is folded to allow expansion :S also don't the antibodies attach to the mast cell AFTER encountering a pathogen (the antigen would've have bonded to them to make that happen)

 

[thats_me]

22) A length of double-stranded DNA contains 120 nucleotides and codes for polypeptide X.
What is the maximum length of polypeptide X?
A. 20 amino acids
B. 40 amino acids
C. 60 amino acids
D. 120 amino acids

correct answer : A

My doubt : how is it A?

Source : 2012 may - june paper_11

For a single strand of DNA 3 nucleotides would form 1 amino acid
Here it's a double stranded DNA so 120/2 =60 nucleotides
Now cross multiply if 3 nucleotide give 1 amino acid
60 nucleotides will give how many amino acids? 60/3=20

 

[thats_me]

Base is part of a nucleotide
Nucleotide is made of sugar,phosphate & nitrogenous base

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s13_qp_12.pdf

Question no. 22 ??
What is the difference btw base pairs and nucleotides??

 

[Busy Buddy]

20) A peptide consists of ten amino acids of four different kinds.
What is the theoretical minimum number of different tRNA molecules required to translate the
mRNA for this peptide?
A. 4
B. 10
C. 12
D. 30

Answer : A

My doubt : how is it an A ?

source : may-june paper_12

 

[thats_me]

20) A peptide consists of ten amino acids of four different kinds.
What is the theoretical minimum number of different tRNA molecules required to translate the
mRNA for this peptide?
A. 4
B. 10
C. 12
D. 30

Answer : A

My doubt : how is it an A ?

source : may-june paper_12

One tRNA has One amino acid so 4 different types of amino acid will need 4 different tRNA

 

[cool.hamza3]

how was the paper guys??

 

[ZaqZainab]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s13_qp_12.pdf

Question no. 22 ??
What is the difference btw base pairs and nucleotides??

when was your exam
i was done with mine by this time

 

[joanna omar]

Anyone please I've got some doubts over here !

Nov 2011 v2 -----> Q16
june 2012 v2 ----->Q27
Nov 2012 v2-----> Q17 and Q38
Nov 2012 v3 ----->Q39

HELP !
Nov 2013 v1/3

Q1 , 7 , 8 and 17 ?

http://server-poddarh.rhcloud.com/paper.html
ZaqZainab

areebaization

 

[ZaqZainab]

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

its given the question 100 cm^3 has 19 cm^3 oxygenated.....

 

[GCE As and a level]

its given the question 100 cm^3 has 19 cm^3 oxygenated.....

hey how was ur exam ???

 

[Busy Buddy]

Why is the answer C ?

 

[joanna omar]

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

Can u explin it to me how did u get the 950 and 625 by using the ratio how?

 

[areebaization]

View attachment 41660
Why is the answer C ?

40 EPG=10 micro metres (0.1mm=10 micrometres)
so radius is (50x10)/40 = 12.5 micrometres

Area of a circle=pi x r x r
=pi x 12.5 x 12.5
= 490 micrometres
=4.9 x 10^2 micrometres

 

[MiniSacBall]

Explain this shit CIE:

http://papers.xtremepapers.com/CIE/...nd AS Level/Biology (9700)/9700_s13_qp_13.pdf
Q39 ms answer D

http://papers.xtremepapers.com/CIE/...nd AS Level/Biology (9700)/9700_w13_qp_12.pdf
Q40 ms answer C

Which freaking retards make the question paper. I am more likely to lose marks because of your shit rather than my own shit.
I am pissed like hell? I find my mistakes/confusions because you make a thousands of mistakes in your god dawm English in the question paper itself.
In many past paper you ask us to name the cells in the figure while those are simple structures, like nucleus.
Da faq CIE. Hope you guys won't go retard while making my qp.
CIE is horrible at English! You guys just freaking have dumb accents, not proper English, You guys need to retake IELTS, go to kinder-garden and start learning.

Any one here explain this, hopefully i have not committed a mistake in reading, or may be i can't read. You guys Try?
Anyone :/// ?

 

[ZaqZainab]

Anyone please I've got some doubts over here !

Nov 2011 v2 -----> Q16
june 2012 v2 ----->Q27
Nov 2012 v2-----> Q17 and Q38
Nov 2012 v3 ----->Q39

HELP !
Nov 2013 v1/3

Q1 , 7 , 8 and 17 ?

http://server-poddarh.rhcloud.com/paper.html
ZaqZainab

Nov 2011 v2 -----> Q16 As temperature decreases(getting colder) the membrane gets less fluid
less fluid means more the unsaturated bonds
and so unsaturated increasing and saturated decrease
june 2012 v2 ----->Q27 all of them are tiny enough to leak from blood to the lymph and all of them are present in the tissue fluid too
Nov 2012 v2-----> Q17 and Q38 q17 what do they mean by an equilibrium? means equal no of molecules on both sides
Diffusion ----> you perfume in a corner of a room at the end of the day you will be able to smell the odor all over the room
Osmosis------> add a drop of color to water in a corner after a while you will see all of the water is colourised
Facilitated diffusion---> same thing as diffusion just with bigger molecules
Active transport--> from lower to higher this is trying to oppose the equilibrium
Q38 if you remove X the primary producer will have 1 less animal feeding on it means it will be more in number
and D will have 1 less animal to feed on D will decrease now A has 1 less animal to eat from but it still has B so it will eat more of B and so A B D are decreasing
where as C increases as it gets most of the food as B is no more there
Nov 2012 v3 ----->Q39 Even idk

Nov 2013 v1/3

Q1 , 7 , 8 and 17 ? which variant?

 

[ZaqZainab]

Can u explin it to me how did u get the 950 and 625 by using the ratio how?

Cross multiplication "
if 100:19
how much will 5000(50dm^3) be
5000*19 /100 do the same for veins

 

[ZaqZainab]

hey how was ur exam ???

Awesome