• We need your support!

    We are currently struggling to cover the operational costs of Xtremepapers, as a result we might have to shut this website down. Please donate if we have helped you and help make a difference in other students' lives!
    Click here to Donate Now (View Announcement)

A level Biology: Post your doubts here!

M

My Name

Messages
4,988
Reaction score
23,955
Points
523
http://papers.xtremepapers.com/CIE/...nd AS Level/Biology (9700)/9700_w10_qp_22.pdf
question1 part c-ii
I don't understand this !

http://papers.xtremepapers.com/CIE/...nd AS Level/Biology (9700)/9700_s10_qp_22.pdf
question5 part d
I don't understand this

http://papers.xtremepapers.com/CIE/...nd AS Level/Biology (9700)/9700_s11_qp_21.pdf
question3 part c ( I know the answer I think but I think I'm not exactly sure ....I need to explain translation in this right?)

http://papers.xtremepapers.com/CIE/...nd AS Level/Biology (9700)/9700_s11_qp_22.pdf
question 5 part b -ii

Is this alright to score three marks?

The phospholipids form a bilayer.It provides fluidity to the membrane and has hydrophilic heads which face outwards into the water and hydrophobic tails which act as a barrier to water soluble substances.
 
A

Awesome12

Messages
2,188
Reaction score
5,558
Points
523
My Name said:
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_w10_qp_22.pdf
question1 part c-ii
I don't understand this !

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s10_qp_22.pdf
question5 part d
I don't understand this

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s11_qp_21.pdf
question3 part c ( I know the answer I think but I think I'm not exactly sure ....I need to explain translation in this right?)

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s11_qp_22.pdf
question 5 part b -ii

Is this alright to score three marks?

The phospholipids form a bilayer.It provides fluidity to the membrane and has hydrophilic heads which face outwards into the water and hydrophobic tails which act as a barrier to water soluble substances.
Click to expand...
1) - Proteins can be modified in several ways. They are usually slightly modified in the Rough E.R, whereas most of the modification occurs in the Golgi Apparatus. Its like proteins are blocks of wood. Now the wood can be modified to make a tree house, or a basic plank consisting of several blocks of wood. Now how exactly does modification occur, or what change occurs that tells us that the protein has been modified? Well, proteins can be modified by

- Addition of prosthetic group (like in Hameoglobin)
- Removal of amino acid
- CIE has been lenient over here, allowing the candidate to mention that the secondary or tertiary structure has been disrupted.


2) - There is no 5 (d)


3) - Yeah exactly. The function of mRNA after it is formed is to act as an auxiliary in the formation of proteins, that is its codon is complementary to the anticodon on the tRNA.


4 - Yeah you could say that, with a slight addition of "The hydrophillic head forms H-bonds with the water"
 
Last edited:
F

fatimarehman

Messages
54
Reaction score
46
Points
28
I want to ask a question regarding the experiment of serial dilution in biology. In this we have to calculate the rate at which the colour change is affected by the dilutions 0.8% of reducing sugar. Please tell me how should we proceed in this experiment. I performed this experiment but it took me 8 min to note the first color change my teacher said that it should take 2-3 min . I added equal amounts of Benedict reagent for standardization. Please also give me tips regarding biology practicals.
 
A

Awesome12

Messages
2,188
Reaction score
5,558
Points
523
Mahnoorfatima said:
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s03_qp_1.pdf
Mcq 4?
Click to expand...
If it has the same water potential, then the length of the strip before and after immersion will be the same (ie, no change in length). Thus the ratios of their lengths will be equal to 1. (Assume that the initial length was 5 cm, then the final length is also 5 cm. 5/5 = 1). Thus by looking from the graph, find the sucrose concentration that corresponds to 1.0
 
princess Anu

princess Anu

Messages
1,229
Reaction score
740
Points
123
Q How can increase in stroke volume and hence cardiac output + RBC count help to compensate the low partial pressure of O2 at high altitudes?
Q How does mixing of oxygenated and deoxygenated blood lead to reduced O2 uptake at the lungs ? The book says,' Supply of O2 to tissues would be inadequate & there would be a reduced diffusion gradient in the lungs, limiting the rate of O2 uptake.'
What exactly does that mean?
 
Last edited:
princess Anu

princess Anu

Messages
1,229
Reaction score
740
Points
123
Can someone suggest an answer for this
Q An interventricular septal defect is an opening in the wall ( septum) that separates the left and right ventricles. Suggest and explain the effect of this defect on blood flow through the heart.
 
ZaqZainab

ZaqZainab

Messages
1,764
Reaction score
3,472
Points
273
C

cool Hassan

Messages
91
Reaction score
93
Points
28
rexsun said:
Hello everybody. I have been confused by the following question for a long time...Please help
The answer for this question is D.
But why can't C be right? I thought that stomata are open because of guard cells but not transpiration.
View attachment 49685
Click to expand...
fact is that transpiration doesnot maintain the water potential... if u say transpiration maintains the water potential then why wilting occurs??
as a matter of fact a plant usually transpires most of the water absorbed in the transpiration
>the most important reason for this is to maintain the temperature..
>then comes the purpose of keeping the stomata open for the gaseous exchange
>however it also does maintain the water potential but to the least extent..
So, thats why most suitable is D.. hope u got the point :)
 
P

Princess1997

Messages
60
Reaction score
86
Points
28
Shada Mohammed said:
what is the chi squared test and the null hypothesis?
Can anyone explain what it's purpose?
Click to expand...
the chi square test is a test that allows us to compare our observed results with our expected one and decide whether or not there is a significant difference between them. we usually take a probability of 0.05 as the critical value, so if the chi answer is less than 0.05 then the differences are significant and we must reconsider our assumptions but if it is greater than 0.05 then the differences are significant and due to chances
 
Shada Mohammed

Shada Mohammed

Messages
110
Reaction score
166
Points
53
Princess1997 said:
the chi square test is a test that allows us to compare our observed results with our expected one and decide whether or not there is a significant difference between them. we usually take a probability of 0.05 as the critical value, so if the chi answer is less than 0.05 then the differences are significant and we must reconsider our assumptions but if it is greater than 0.05 then the differences are significant and due to chances
Click to expand...

thanks a lot but I think in the last part you really have meant that if the chi square value is greater than the 0.05 (the critical value) this means that the differences are not significant and the null hypothesis is to be accepted and we will reconsider our assumptions when the chi square value is less than 0.05 so ; as a result, the hypothesis would be rejected.
 
You must log in or register to reply here.
Top