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A level Biology: Post your doubts here!
- Thread starter XPFMember
- Start date
"Over 60 % of candidates were able to correctly link a disease with the method of controlling spread, treatment and causative agent."
The cell surface membranes of plants adapted to cold conditions change as the weather gets colder, allowing the plants to carry out exocytosis. Which change occurs?
A a decrease in the ratio of proteins to saturated phospholipids
B a decrease in the ratio of unsaturated phospholipids to saturated phospholipids
C an increase in the ratio of proteins to unsaturated phospholipids
D an increase in the ratio of unsaturated phospholipids to saturated phospholipids
A a decrease in the ratio of proteins to saturated phospholipids
B a decrease in the ratio of unsaturated phospholipids to saturated phospholipids
C an increase in the ratio of proteins to unsaturated phospholipids
D an increase in the ratio of unsaturated phospholipids to saturated phospholipids
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No, A is the correct answer. In questions related to Inf diseases always think carefully, they are very tricky. Actually both are correct, but how is malaria transmitted in the first place(normally and directly), by the Female Anopheles Mosquito not by blood transfusions. Now, cholera is transmitted when some contaminated faeces
are in the water and you drink it, wash your food with it etc and therefore you literally ingest it
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Yes there is, if you study the structure of both of them you will realize how and why they bond together by 2 Hydrogen bonds. Luckily that in depth info is not there in our specification.
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Briefly, Purines are large (2 rings) and Pyrimidines small (1 ring).
Between the two DNA strands, there's space for three only, so the only possible bonding is 1 Purine + 1 Pyrimidine.
So that's why Adenine and Guanine, which are both Purines, cannot bond together (Too large)
However, this still does not explain other combinations we could think of which cannot occur, like adenine (purine) and cytosine (pyrimidine). [These two never bond, though they have "three ring width" together]
To explain those, you'll have to study their structures like Mahmood said above.
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It should be D, and I'm guessing people might've thought B.
Reason is, at B, the chromosomes split, but the centromeres never detached from the spindle fibre. After all, the spindle fibers have to be attached to the centromere for it to be able to pull them apart to opposite poles! Only at the end when they're done pulling them all the way can they let go.
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I'm confused because it's supposed to be A!!
"Over half of all candidates realised that the presence of a nuclear membrane in eukaryotes and its
breakdown during mitosis would result in a slower division than in prokaryotes."
could it be related to the size ....i mean...more genes...so slower ...however, thats only possible in D
Mahmood Magdy do u have any ans?
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What I mean is isn't the answer supposed to be A? You're saying it's either C or D??
D says bigger size but this probably means physical size, you're talking about size of genome...
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HELP
i did A in the prev paper and the MS stated its D.
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Not really sure but It can't be related to size of chromosomes etc because that takes place in during the S Phase not 'division'. I guess C is incorrect becuz centrioles speed up eukrayotic division coz of the movement of organelles etc, they are saying prokaroytes are faster, so it can't be a reason . But to why D is wrong, the only logical explanation would be becuz as the cells are smaller maybe everything will be relative, for ex small conc of enzymes etc.
But A is correct becuz the eukaryotes still have to break down the nuclear membrane whereas Prokaryotes can just replicate their DNA and divide directly.
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The Answer is A I guess. Simply because carcinogens have to react with the DNA first and that causes mutation, therefore D is wrong. Now why B and C are wrong is because the accumulation of the mucus does not cause inflammation, but when bacteria get trapped in it and they start reproducing and producing toxins etc which then causes inflammation and attracts Phagocytes.
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Thanks bro
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It should be D, since in cold conditions, fluidity of the cell membrane decreases.
Unsaturated phospholipids have unsaturated fatty acid tails, which have a "kink" in their shape, and make the bilayer more fluid.
