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AS Biology P1 MCQs Preparation Thread

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Hey guys, this is a J/11/11 question 14
Some inhibitors of enzyme reactions bind to the enzyme/substrate complex.
which statements about this type of inhibtion are correct?
1 The active site changes shape
2 The inhibitor is non competitive
3 The initial rate of reaction is reduced
4. The maximum rate of reaction is increased
A. 1 and 2 only B. 1 and 3 only C 2 and 3 only D. 2, 3, 4
The answer is C, which includes 2 and 3. Why 1 is not included? Pls help
 
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Hey guys, this is a J/11/11 question 14
Some inhibitors of enzyme reactions bind to the enzyme/substrate complex.
which statements about this type of inhibtion are correct?
1 The active site changes shape
2 The inhibitor is non competitive
3 The initial rate of reaction is reduced
4. The maximum rate of reaction is increased
A. 1 and 2 only B. 1 and 3 only C 2 and 3 only D. 2, 3, 4
The answer is C, which includes 2 and 3. Why 1 is not included? Pls help
there are 2 types of non competitive inhibition
one is by binding to the allosteric site (ie. anywhere not on active site) and change the structure of active site. this type of inhibition only occurs when the substrate is NOT bond to enzyme yet.

The question states that the inhibitor binded to the enzyme/substrate complex, this is the second type of non competitive inhibition.
This inhibition can occur either like a competitive inhibitor by binding on the enzyme active site but permanently, or by binding on to the enzyme substrate complex and stop formation of product (the complex can only revert back to reactants, or an enzyme inhibitor complex).
Active site shape is not changed in this way.
 
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there are 2 types of non competitive inhibition
one is by binding to the allosteric site (ie. anywhere not on active site) and change the structure of active site. this type of inhibition only occurs when the substrate is NOT bond to enzyme yet.

The question states that the inhibitor binded to the enzyme/substrate complex, this is the second type of non competitive inhibition.
This inhibition can occur either like a competitive inhibitor by binding on the enzyme active site but permanently, or by binding on to the enzyme substrate complex and stop formation of product (the complex can only revert back to reactants, or an enzyme inhibitor complex).
Active site shape is not changed in this way.
Your explanation is really helpful. Thank you! :D
 
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#18 answer is A because mitosis is a form of asexual reproduction
characteristics: daughter cell and parent cells are identical ie. same jobs, DNA unchanged
so B,C,D is all correct
and semi conservative replication occurs before mitosis during interphase so A is wrong

#40
we find the energy transferred to tertiary, so we deduct all energy loss 23000 - 8000 - 10500- 4200=300
300/23000 x100% = 1.3%
 
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Hey anyone? For question 21 in June 2005 exam,
How could I identify metaphase?
 

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Hey anyone? For question 21 in June 2005 exam,
How could I identify metaphase?
firstly question states its either anaphase or metaphase
metaphase is when the chromosomes line up at equator ie. not separated
anaphase is when its separated to chromatids

in the picture they're not separated so it must be metaphase
 
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Thank you very much! If possible, could you pls help me another onE?
Nov 2007 Q19
Shouldn't statement 4 chromosomes uncoil be in the first order?
 

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Thank you very much! If possible, could you pls help me another onE?
Nov 2007 Q19
Shouldn't statement 4 chromosomes uncoil be in the first order?
no, at prophase the chromosomes coil up
and at the end of telophase they uncoil to get ready to be replicated via semi conservative replication in interphase (which is not part of mitotic cycle)
 
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Hello, anyone could explain Q21 in Nov 2006 for me?
DNA is semi conservative replication, DNA has 2 strands
at the start it is all made of 15N. so 15N - 15N DNA
it grows replicate under 14N
so all 15N will pair with a 14N so 15N-14N DNA with a overall weight of 14.5, this is lighter so this is at Y after centrifuge.

and for next generation still growning under 14N
half of the original strands are now 14N, and half are 15N
so 14N combines with 14N forming 14N-14N, and 15N combines with 14N forming 15N-14N. so 50% at X which is lightest 14N-14N strand, and 50% at Y which is 14N-15N
 
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