A level Biology: Post your doubts here!

[Doggybros]

I keep seeing "Kupffer cells" in the old past papers....was this portion removed from the syllabus or should I go further into it?

 

[sagystu]

does any body have like summery or revision notes for the A2 bio thanksss alot

 

[Thampi4]

I keep seeing "Kupffer cells" in the old past papers....was this portion removed from the syllabus or should I go further into it?

I keep seeing "Kupffer cells" in the old past papers....was this portion removed from the syllabus or should I go further into it?

They r removed

 

[Thampi4]

Questions where they ask with reference to fig. Something such as a graph

What points r the examiners looking for other than mentioning figures?

 

[megamind]

What about NAD being a co enzyme so if base pairing is wrong due to mutation then an incorrect co enzyme is synthesized in protein synthesis so NAD won't be a good hydrogen carrier hence respiration cant take place.

dude my question on importance of base pairing had nothing to do with NAD

 

[megamind]

U know, the fact that Hydrogen bonding is known to be strong, i don't think that by keeping bases inside would 'protect' the latter, i don't think its a strong argument here. However, what i have said previously, is an answer accepted by examiners. try to see other people's opinions about what you have said.

thanks anyway, i lack self confidence

 

[PANDA-]

ive got another question

explain the importance of base pairing pleeasee?

Not sure about this, but I'll try...

Base pairing helps to keep the DNA molecule stable, as if the bases were exposed, and not paired inwards in the way they are, they would react with cellular fluids, which would cause the loss of the DNA information. Also, base pairing occurs with hydrogen bonding, and individual hydrogen bonds are easy to break (mind that many hydrogen bonds are strong, but few or individual can be broken easily), this helps when the DNA must split for DNA replication or protein synthesis.

 

[raamish]

hey guys what is the purpose of toxins produced by the malarial parasites. Do they cause any of the symptoms of malaria. Culdnt understand from the markscheme.

QP:http://www.freeexampapers.com/index... Level/Biology/CIE/2002 Nov/9700_w02_qp_2.pdf
MS:http://www.freeexampapers.com/index... Level/Biology/CIE/2002 Nov/9700_w02_ms_2.pdf

 

[raamish]

Hey guys has the syllabus changed from 2012 to 2013 because im giving bio retake so if some change has occured can somebdy let me know

 

[PANDA-]

hey guys what is the purpose of toxins produced by the malarial parasites. Do they cause any of the symptoms of malaria. Culdnt understand from the markscheme.

QP:http://www.freeexampapers.com/index.php/directory/download?location=A Level/Biology/CIE/2002 Nov/9700_w02_qp_2.pdf
MS:http://www.freeexampapers.com/index.php/directory/download?location=A Level/Biology/CIE/2002 Nov/9700_w02_ms_2.pdf

Did you mean the question that says...
"Outline the likely effects..."?

Please state the question number, makes everything easier.

 

[raamish]

Did you mean the question that says...
"Outline the likely effects..."?

Please state the question number, makes everything easier.

Its qs 5c.

And w03 QP: http://papers.xtremepapers.com/CIE/...and AS Level/Biology (9700)/9700_w03_qp_2.pdf
MS: http://papers.xtremepapers.com/CIE/...A and AS Level/Biology (9700)/9700_w03_ms.pdf
qs 4b) when starch hydrolysed by amylase will amylase be formed or maltose be formed? and how is benedicts reaction being carried out. Dont we have to heat the solution for brick red ppt to be produced. But in this exp. we have to keep the temp at 25'c

 

[Amy Bloom]

thanks anyway, i lack self confidence

Don't worry, get a good grasp of the topic, u'll be good

 

[PANDA-]

hey guys what is the purpose of toxins produced by the malarial parasites. Do they cause any of the symptoms of malaria. Culdnt understand from the markscheme.

QP:http://www.freeexampapers.com/index.php/directory/download?location=A Level/Biology/CIE/2002 Nov/9700_w02_qp_2.pdf
MS:http://www.freeexampapers.com/index.php/directory/download?location=A Level/Biology/CIE/2002 Nov/9700_w02_ms_2.pdf

For this first question... The answer is pretty clear in the MS.
When the malarial parasite invades an RBC, it makes it more rigid, making it harder for the RBC to move through blood vessels, so eventually it will rupture, this causes the number of RBC's to reduce, and therefore the number of haemoglobin molecules, so less oxygen can be carried around the body, causing anaemia.

For the second question...
The rate can be measured by measuring the amount of products produced per time. Starch must be placed in a test tube and a few drops of enzyme must be added, then quickly after, a few drops of Benedict's solution must be added, and start the stopwatch, the time taken for the starch to fully hydrolyse is the time taken for the solution to turn brick red (a colorimeter must be used for accurate results). Then time must be substituted in 1/time to get the rate of reaction.

 

[kaushar]

need help for serial dilution plzzz....

 

[littlecloud11]

need help for serial dilution plzzz....

http://toolboxes.flexiblelearning.n...oratory/studynotes/SNHowToPerfrmSrlDilutn.htm
this might help.

 

[kaushar]

thnks i have view the site just before u send me the link hihi

 

[Doggybros]

Do I need to study the Ornithine cycle or was it removed from syllabus? Only answer if you're sure please.

 

[Shreeram]

please help!! do we draw double circle when drawing the xylem vessels while drawing the vascular bundle

 

[MKh@lid]

Hey guys has the syllabus changed from 2012 to 2013 because im giving bio retake so if some change has occured can somebdy let me know

Why not check it out for yourself?? http://papers.xtremepapers.com/CIE/...A and AS Level/Biology (9700)/9700_y13_sy.pdf

 

[megamind]

Not sure about this, but I'll try...

Base pairing helps to keep the DNA molecule stable, as if the bases were exposed, and not paired inwards in the way they are, they would react with cellular fluids, which would cause the loss of the DNA information. Also, base pairing occurs with hydrogen bonding, and individual hydrogen bonds are easy to break (mind that many hydrogen bonds are strong, but few or individual can be broken easily), this helps when the DNA must split for DNA replication or protein synthesis.

I asked my teacher told me this-

Purines with prymidines, ocuppy same space between the backbone strands,space constant more stable
complementary base-pairing(ATCG,hydrogen bond)is crucial to for replication and gene expression.,DNA is semi-conservative