AS Biology P1 MCQs Preparation Thread

[egy]

okazaki fragments?? i kinda understand what ur getting at but could u explain this term?

OK
in DNA replication the DNA both strands act as a template , one DNA strand will be catalyzed continuously and the other strand incontinuous

in incontinuous replication small sections of the DNA is formed by DNA polymerase enzyme (( which catalyzes replication ))
and those sections will be linked by the enzyme DNA ligase and finally two DNA molecules is formed (( semi conservative replication )) .

 

[kinglynx]

https://fbcdn-sphotos-a.akamaihd.ne...6933426535_664491534_12390334_548868376_n.jpg

Can anyone explain why the answer is B and not A ?

(Red blood cell question)

THANK YOU

 

[kinglynx]

never mind i know now haha

 

[JulyMei]

Can anyone explain this graph? I don't really get it.. Thanks in advance.

anyone????

 

[00tanveer]

It's A bro.... Anyone else wanna give a try??

 

[rogue94]

anyone????

Xylem transports water and mineral ions so the sucrose concentration in xylem is insignificant (some surcrose may entered xylem by diffusion.) The graph/lines of phloem and leaves are identical indicating the active loading of sucrose from leaves to phloem. From 0 00 to 06 00 no photosynthesis takes place so no sucrose is formed and the sucrose already present in the plant is stored or hydrolysed. From 06 00 to 18 00 photosynthesis takes place, and sucrose is manufactured. Thus, the concentration of sucrose in leaves increases, and as this sucrose is loaded into phloem sieve tubes the concentration of sucrose in the phloem also increases within the same time period. The concentration peaks at 21 00 for both phloem and leaves after which it decreases as no photosynthesis is taking place (the concentration keeps on increasing till 21 00 even after there is no photosynthesis taking place, since the glucose manufactured from photosynthesis is still being used to form sucrose).

 

[Jaf]

https://fbcdn-sphotos-a.akamaihd.ne...6933426535_664491534_12390334_548868376_n.jpg

Can anyone explain why the answer is B and not A ?

(Red blood cell question)

THANK YOU

Dude, atleast take the picture right. -_- It's tilted and not even complete.

 

[SalamH]

Can you upload this book if possible please?

ya pleeeeeez it wud be of use to many of us

 

[JulyMei]

Xylem transports water and mineral ions so the sucrose concentration in xylem is insignificant (some surcrose may entered xylem by diffusion.) The graph/lines of phloem and leaves are identical indicating the active loading of sucrose from leaves to phloem. From 0 00 to 06 00 no photosynthesis takes place so no sucrose is formed and the sucrose already present in the plant is stored or hydrolysed. From 06 00 to 18 00 photosynthesis takes place, and sucrose is manufactured. Thus, the concentration of sucrose in leaves increases, and as this sucrose is loaded into phloem sieve tubes the concentration of sucrose in the phloem also increases within the same time period. The concentration peaks at 21 00 for both phloem and leaves after which it decreases as no photosynthesis is taking place (the concentration keeps on increasing till 21 00 even after there is no photosynthesis taking place, since the glucose manufactured from photosynthesis is still being used to form sucrose).

but how do i know the answer? the answer is B though.. about active transport..

 

[JulyMei]

View attachment 11918
It's A bro.... Anyone else wanna give a try??

I think we can use "elimination" to get the answer..

B, it's planting of leguminous crops, it can help in nitrogen fixing
C, animal waste is nitrogenous waste, it can increase amino acids and undergo deamination, nitrification and form nitrates
D, urea, same explanation as C..

Did i guessed that? hahaha..

 

[rogue94]

but how do i know the answer? the answer is B though.. about active transport..

Elimination can be employed here. Option D is factually incorrect whereas options A, B and C are factually correct. However, the conclusions in options A and C cannot be drawn from the results/graph. Only the statement in option B can be drawn as a conclusion from the results/graph. This is because the graph/lines of leaves and phloem are identical.

 

[JulyMei]

Elimination can be employed here. Option D is factually incorrect whereas options A, B and C are factually correct. However, the conclusions in options A and C cannot be drawn from the results/graph. Only the statement in option B can be drawn as a conclusion from the results/graph. This is because the graph/lines of leaves and phloem are identical.

Oh.. I see.. Ok.. Thanks a lot!

Can I ask this too?
Why can't the answer be C?

 

[rogue94]

Oh.. I see.. Ok.. Thanks a lot!

Can I ask this too?
Why can't the answer be C?

0 kPa is the water potential of pure water, whereas water in xylem contains dissolved mineral ions so it has a lower (less than o) water potential.
The question asks about salty water which is unsuitable for growth. Water moves from the xylem to the soil water (which is why it is unsuitable for growth, since water is being lost from the roots.) As water moves from less negative to more negative water potential, the correct option is D (from -700 to -1800). Options A and C are easily eliminated since both xylem and soil water can't have a water potential of o kPa (only pure water does) whereas option B indicates movement of water from soil water to xylem which is the opposite of what the question asks.

 

[xxfarhaxx]

pls do solve ths fr me..its frm sum old ppr i gues..

Q1. the DNA code for glumatic acid is CTC or CTT.the code for valine is CAA or CAT. In sickel cell heamoglobin , valine is present instead of glumaic acid. Assuming a single base pair substitution has occured, what is the mRNA code in the affected mutant?
A. CUU
B. GAA
C.GAG
D.GUA
E. GUU
ans: D


Q2. Compared with single ribosomes, polyriboseomes increase the efficiency of protien synthesis. how is ths achieved?
A.different protein molecules can be made simultaneously.
B. each copy of a protein can be made rapidly.
C. more than one copy of the mRNA can be read at the same time.
D.many copies of the same protein can be made simultaneously from one mRNA molecule.
ans: ???

 

[rogue94]

pls do solve ths fr me..its frm sum old ppr i gues..

Q1. the DNA code for glumatic acid is CTC or CTT.the code for valine is CAA or CAT. In sickel cell heamoglobin , valine is present instead of glumaic acid. Assuming a single base pair substitution has occured, what is the mRNA code in the affected mutant?
A. CUU
B. GAA
C.GAG
D.GUA
E. GUU
ans: D


Q2. Compared with single ribosomes, polyriboseomes increase the efficiency of protien synthesis. how is ths achieved?
A.different protein molecules can be made simultaneously.
B. each copy of a protein can be made rapidly.
C. more than one copy of the mRNA can be read at the same time.
D.many copies of the same protein can be made simultaneously from one mRNA molecule.
ans: ???

For Q1. options A, B and C are easily eliminated since they are not complementary to the DNA codes for valine. Both option D and E are complementary to the DNA codes for valine, but since the question asks about mutation in which single nucleotide/base has been substituted (from CTT of glutamic acid to CAT of valine, with single substitution of second T by A). So, the mRNA codon has to be complementary to CAT (GUA-option D) and not CAA (GUU-option E), therefore D is correct!

For Q2. option D is correct, since it is a fact that many ribosomes (also known as polyribosomes or polysomes) move along one mRNA molecule to synthesis many copies of the same protein/polypeptide.

 

[KurayamiKimmi]

OK
in DNA replication the DNA both strands act as a template , one DNA strand will be catalyzed continuously and the other strand incontinuous

in incontinuous replication small sections of the DNA is formed by DNA polymerase enzyme (( which catalyzes replication ))
and those sections will be linked by the enzyme DNA ligase and finally two DNA molecules is formed (( semi conservative replication )) .

thanks ^^

 

[Ahmed Ali Akbar]

https://fbcdn-sphotos-a.akamaihd.ne...6933426535_664491534_12390334_548868376_n.jpg

Can anyone explain why the answer is B and not A ?

(Red blood cell question)

THANK YOU

king.....sodium ions doesnt pass through phospholipid but instead pass through hydrophilic channel.....therefore statement 2 is wrong...

 

[Knight]

Q;2, 3, 10, 16, 30
help needed......answers with description plz

 

[KurayamiKimmi]

http://www.xtremepapers.com/papers/...and AS Level/Biology (9700)/9700_s06_qp_1.pdf
q no 30 -the ans ic C
i dont need help in explaining-the logic behind-the answer but simply how the calculation is done
i get 0.04 s and when u divide it by 0.6 u get 0.07 -->C (which is the ans )....but why do you divide it ?

 

[rogue94]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s06_qp_1.pdf
q no 30 -the ans ic C
i dont need help in explaining-the logic behind-the answer but simply how the calculation is done
i get 0.04 s and when u divide it by 0.6 u get 0.07 -->C (which is the ans )....but why do you divide it ?

You don't carry out any division, u simply add the time between 1 and 2, and the time between 3 and 4. This sum is approximately equal to 0.07 s