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AS Biology P1 MCQs Preparation Thread

Jaf

Jaf

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00tanveer said:
View attachment 12170
The answer is A in the mark scheme, but why is it not C?? Heart is one of the chapters giving me a tough time. :(
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It's not C because athletes, who have greater cardiac outputs, have a lower blood pressure. Hence it can't be C or D. Also, greater cardiac output = more oxygen supplied to muscles = more carbon dioxide taken in.
I don't know why the impulses in the vagus nerve wouldn't increase. :oops: The vagus nerve decreases the heart rate.
 
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geek101

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Jaf said:
It's not C because athletes, who have greater cardiac outputs, have a lower blood pressure. Hence it can't be C or D. Also, greater cardiac output = more oxygen supplied to muscles = more carbon dioxide taken in.
I don't know why the impulses in the vagus nerve wouldn't increase. :oops: The vagus nerve decreases the heart rate.
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the cardiac output is sort of a long term thing, like when a person exercises regularly their cardiac output increases but not for that instant its for a long time. so the vagus nerve causes only a temporary change in the heart rate, this is instantaneous and does not affect the cardiac output.
 
Jaf

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geek101 said:
the cardiac output is sort of a long term thing, like when a person exercises regularly their cardiac output increases but not for that instant its for a long time. so the vagus nerve causes only a temporary change in the heart rate, this is instantaneous and does not affect the cardiac output.
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Ufff genius! :D
Thanks!
 
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Paparazzi478 said:
CAN SOMEONE PLEASE HELP ME WITH THIS QUESTION
http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Biology (9700)/9700_w05_qp_1.pdf
QUESTION NO. 23 !!!!!
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ok here the trick or rule or whatever.....that the DNA and tRNA will have the same triplet code, BUT DNA has T instead of U, so replace the Us in tRNA codes with T to get the DNA code..... ok in this question...the first a.acid is glycine, which is either CCA or CCU, so apply the rule, the DNA molecule will either have CCA or CCT, therefore C and D are eliminated. next is the arg thing, which is either UCC or GCG, so the DNA molecule will have either TCC or CGC, both A and B have it. Next is lysine which is either UUC or UUU...sooo again, the DNA could either have TTC or TTT...and B has it A doesnt! tadaa :)

ps. you can even find the complementary mRNA codons and then find DNA...theres more chance of error there.
 
Oliveme

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Soldier313 said:
Can someone please help me with qn 14, 16, 25, 31 and 40
Qn Paper: http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Biology (9700)/9700_w11_qp_11.pdf
ms: http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Biology (9700)/9700_w11_ms_11.pdf
Tx and God bless
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16) endocytosis involves proteins and cholesterol as well as lipids. it's when the cell membrane curves inwards which requires flexibility and is gained by cholesterol molecules within the plasma membrane. Osmosis does not only involve proteins, the whole plasma membrane is involved in the process. so 2 and 4 are definitely wrong which leaves 1 and 3. so answer is C.
25) arteries have thick elastic layers for evening out blood flow and avoiding bursting. so B because if arteries didn't have this thick layer, the blood would flow in disproportion, less in some places and too much blood clogged in another place. it would not be able to withstand the high pressure if there wasn't a tough layer and would probably burst.
31) tar doesn't deposit in arteries, it reaches the respiratory system, the trachea and the bronchioles and gets deposited there. nicotine causes high blood pressure and increases the production of fibrogen which causes lumen of blood vessels to get small as plaque gets clogged up there. carbon monoxide binds irreversibly with hemoglobin. so answer is C.
I'm sorry I can't help with the others as my concepts about them are very clear. hope, though, that I helped. :)
 
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geek101

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Soldier313 said:
Can someone please help me with qn 14, 16, 25, 31 and 40
Qn Paper: http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Biology (9700)/9700_w11_qp_11.pdf
ms: http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Biology (9700)/9700_w11_ms_11.pdf
Tx and God bless
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14 - this is a crazy question :p actually the plant cell walls form hydrogen bonds with water molecules so sort of forming a layer of water around them...and so they sort of restrict the movement of water inside the cells...the second part of D is understandable.

40 - the curves for producers and primary consumers will rise simultaneously so thats C and D. now the producer population will rise before the rise in the population of p. consumers so the graph of producers will be behind the p. consumer graph and C is behind D so C is producers and D is primary consumers. so the answer is D.
otherwise B is light intensity apparently...and A is nutrients...they rise in winters cuz there are less decomposing bacteria and so they remain in the lake...
 
JulyMei

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Nibz said:
Low pulse rate = stronger heart, i.e person A's heart can pump more blood and more oxygen out with one pump than the other three persons with comparatively higher pulse rates.
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how do you know low pulse rate = stronger heart?
 
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