• 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
Noor Mohammad said:
And finally....
Click to expand...
Thank you for posting these.
Im sure alot of people might find them helpful.
You can also create a thread if you like.
OR have a link of this in your signature,because not many people may see the Bio doubts thread.
Just one small question are these for CIE A levels or umm general..because I think some topics have some extra information.:)
 
Last edited:
B

bakhita

Messages
237
Reaction score
266
Points
73
My Name said:
This is the old edition so the answer is No.This is because that there have been changes in syllabus,some topics have been removed for example Ecology and some have been added fro example a bit more about telomeres and stuff.

The latest edition is this one:http://assets.cambridge.org/97811076/36828/cover/9781107636828.jpg
But my teacher said she is not completely satisfied with it either.
I am currently using the 3rd edition and I was thinking of taking pictures of the pages that are not in my book from a friends book. :) Ive seen the 4th edition it is quite similar to the 3rd but obviously changes are there.
Click to expand...
that of course I could match the topics with the syllabus, and I've two or three other books as well, I could cover from there! don't you think it will be fine then?
 
M

My Name

Messages
4,988
Reaction score
23,955
Points
523
bakhita said:
that of course I could match the topics with the syllabus, and I've two or three other books as well, I could cover from there! don't you think it will be fine then?
Click to expand...
Yes, you can do that.If you have more than one book to refer to than thats great!You asked if that book was enough so that was a no.
Yes,you can In sha Allah it will be fine. :)
qwertypoiu and SadiaMaryam what do you say?
 
B

bakhita

Messages
237
Reaction score
266
Points
73
My Name said:
Yes, you can do that.If you have more than one book to refer to than thats great!You asked if that book was enough so that was a no.
Yes,you can In sha Allah it will be fine. :)
qwertypoiu and SadiaMaryam what do you say?
Click to expand...
haha...what will Sadia Maryam say? she is my sis and sitting in the next room to me! I could just go and ask her personally! She thinks I should first try this Mary Jones book and then see what's left and cover that from the other two books! Actually, I just want to focus on one book, so that I can revise that better and the rest I can cover from the other books!
 
SadiaMaryam

SadiaMaryam

Messages
233
Reaction score
307
Points
73
My Name said:
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_w12_qp_12.pdf
question 15
30 I just cant seem to remember this graph and when valves and stuff! :(
33 What about 2?
34
Click to expand...
#15. Pospholipid membrane is involved in cytokinesis to divide the cytoplasm of one cell into two. It is a controlling barrier for water, gases etc to get into or out of the cells. Phagocytosis occurs when membrane engulfs something by folding around the substance. So, only D is one which is not its function, I've never read it binds with water molecules for surface membrane stability ( cholesterol molecules are involved in membrane stability and fluidity)

#30
upload_2015-11-11_9-2-50.png

Blood comes to left atrium from pulmonary vein, this causes the atria to contract (atrial systole). Atrio-ventricular valves are valves between the atrium and ventricle. They are closed here because blood stays in atria for about 0.1 second.
Blood then flows into ventricles after the atrio-ventricular valves have opened (u can imagine it like a door between atrium and ventricle). Now the pressure must increase in ventricle, therefore there is a higher peak of curve at this point.
When there is a high pressure in the ventricle, it contracts (ventricular systole), it shuts the atrioventricular valves and along with that opens the semilunar valves to allow blood to flow to aorta and this the point where pressure in aorta begins to rise.
Ventricle muscle then relaxes (ventricular diastole), this causes pressure to drop and semilunar valves close because pressure is high in aorta now than in ventricle.
High pressure blood in pulmonary vein then again flows into ventricle and of course it can happen if atrio-ventricular valves are open.

#33: Heart failure is related to fatty materials deposit and blockage in "coronary artery", not in other arteries and veins
 
M

My Name

Messages
4,988
Reaction score
23,955
Points
523
bakhita said:
haha...what will Sadia Maryam say? she is my sis and sitting in the next room to me! I could just go and ask her personally! She thinks I should first try this Mary Jones book and then see what's left and cover that from the other two books! Actually, I just want to focus on one book, so that I can revise that better and the rest I can cover from the other books!
Click to expand...
Haha ohkay I had no idea about that. :p
If you're focusing on ONE book then let it not be an old edition one.But yes it is a good idea to finish up portions of syllabus from other books.
You can also use the revision guide for revision.But just make sure you cover up everything from the syllabus.
 
M

My Name

Messages
4,988
Reaction score
23,955
Points
523
SadiaMaryam said:
#15. Pospholipid membrane is involved in cytokinesis to divide the cytoplasm of one cell into two. It is a controlling barrier for water, gases etc to get into or out of the cells. Phagocytosis occurs when membrane engulfs something by folding around the substance. So, only D is one which is not its function, I've never read it binds with water molecules for surface membrane stability ( cholesterol molecules are involved in membrane stability and fluidity)

#30
View attachment 57591

Blood comes to left atrium from pulmonary vein, this causes the atria to contract (atrial systole). Atrio-ventricular valves are valves between the atrium and ventricle. They are closed here because blood stays in atria for about 0.1 second.
Blood then flows into ventricles after the atrio-ventricular valves have opened (u can imagine it like a door between atrium and ventricle). Now the pressure must increase in ventricle, therefore there is a higher peak of curve at this point.
When there is a high pressure in the ventricle, it contracts (ventricular systole), it shuts the atrioventricular valves and along with that opens the semilunar valves to allow blood to flow to aorta and this the point where pressure in aorta begins to rise.
Ventricle muscle then relaxes (ventricular diastole), this causes pressure to drop and semilunar valves close because pressure is high in aorta now than in ventricle.
High pressure blood in pulmonary vein then again flows into ventricle and of course it can happen if atrio-ventricular valves are open.

#33: Heart failure is related to fatty materials deposit and blockage in "coronary artery", not in other arteries and veins
Click to expand...
Thank you so much!
You wrote so much,like you typed put a para from the book.:p
Remembering all this is a tough job.In sha Allah I will do it.Thanks again.
 
SadiaMaryam

SadiaMaryam

Messages
233
Reaction score
307
Points
73
My Name said:
Thank you so much!
You wrote so much,like you typed put a para from the book.:p
Remembering all this is a tough job.In sha Allah I will do it.Thanks again.
Click to expand...
you'r welcome:)
hehe..not from any book, my own words and my own image:p
I was going to explain a bit more for question 30
like: you can first learn the names of the valves. There are only two types, atrio-ventricular and semilunar. Atrio-ventricular are two types (tricuspid and bicuspid) and they are between ventricle and atrium and semilunar are between atrium and vena cava on the right and between atrium and pulmonary vein on the left.
and yes you can this type of question by asking yourself which valve would open so that pressure would increase at a particular point.

#34:
100 cm3 is 0.1 dm3 (100/1000) carries 19cm3 of O2 in arteries. So 5 dm3 will carry 950 cm3 of O2
100 cm3, 0.1 dm3 carries 12.5 cm3 of O2 in veins. So, 5 dm3 will carry 625 cm3 of O2
But I can't understand clearly why, but the answer is when we subtract 625 from 950... may be because 950-625 = 325 is the amount of Oxygen which is neither in arteries, nor in veins but comes from lungs:p
 
M

My Name

Messages
4,988
Reaction score
23,955
Points
523
SadiaMaryam said:
you'r welcome:)
haha..not from any book.
I was going to explain a bit more for question 30
like: you can first learn the names of the valves. There are only two types, atrio-ventricular and semilunar. Atrio-ventricular are two types (tricuspid and bicuspid) and they are between ventricle and atrium and semilunar are between atrium and vena cava on the right and between atrium and pulmonary vein on the left.
and yes you can this type of question by asking yourself which valve would open so that pressure would increase at a particular point.

#34:
100 cm3 is 0.1 dm3 (100/1000) carries 19cm3 of O2 in arteries. So 5 dm3 will carry 950 cm3 of O2
100 cm3, 0.1 dm3 carries 12.5 cm3 of O2 in veins. So, 5 dm3 will carry 625 cm3 of O2
But I can't understand clearly why, but the answer is when we subtract 625 from 950... may be because 950-625 = 325 is the amount of Oxygen which is neither in arteries, nor in veins but comes from lungs:p
Click to expand...
Alright.Thanks again.
Best of luck!
 
SadiaMaryam

SadiaMaryam

Messages
233
Reaction score
307
Points
73
donewithtime80 said:
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_w14_qp_42.pdf

q:2, b

please explain the question and why the answer is VEGF?

TIA
Click to expand...
Question says VEGF is a growth factor released by tumors. It makes sources for nutrition of tumors and it does so by causing nearby blood vessels to grow branches into tumor.
Antibodies have specific shapes that can bind only to particular antigens, hence destroy them. One such antibody to destroy VEGF is Avastin.
Now, what substance will be used to produce this antibody by hybridoma in which we insert the foreign particle, say antigen into mouse and the mouse's lymphocytes produce antibodies specific to VEGF.
atibody specific to VEGF can only be produced by mouse if it has really encountered VEGF. So, to produce antibody specific to VEGF, VEGF itself is inserted into mouse.
 
SadiaMaryam

SadiaMaryam

Messages
233
Reaction score
307
Points
73
donewithtime80 said:
Can u please explain this also SadiaMaryam
Click to expand...
When I did this, I was able to make the rest points but not this. I'm not sure but I think this statement here means that as the humanized antibodies are not rejected by immune response they can work effectively without many side effects. And without risk of many side effects, we can use different treatments to find out the particular treatment which works for particular target cells.
 
qwertypoiu

qwertypoiu

Messages
924
Reaction score
1,096
Points
153
My Name said:
http://papers.xtremepapers.com/CIE/...and AS Level/Biology (9700)/9700_w04_qp_1.pdf
question
7.answer is A.I had marked B.In which conditions do we add HCl before the Bendicts test ?
Click to expand...
Benedict's test is used to test for REDUCING sugars. All monosaccharides are reducing sugars, but only SOME disachharides are reducing sugars. For example, maltose is a reducing sugar, but sucrose is not a reducing sugar.

So how do we test for such non-reducing disachharides? Just break them down! Once sucrose is broken down (hydrolysed), monosaccharides are formed (fructose and glucose), which ARE reducing.

So if you do the Benedict's test and nothing changed, and then you tried after hydrolysis by HCl and it gave you positive result, it's a confirmation of existence of non-reducing sugars.

Also, if you did the Benedict's test and it turned red, and then you did the test again after hydrolysis by HCl, and the solution turned a DARKER red, that means there must be reducing AND non-reducing sugar in the mixture.

So in your question, the main keyword is "only". B shows that there is a non-reducing sugar, but there is also a reducing sugar in that one! We don't want the reducing, we only want non-reducing (sucrose, as specified by the question)
So the answer should be A.
Hope that's clear.
 
You must log in or register to reply here.
Top