AS Biology P1 MCQs Preparation Thread

[Nibz]

just checked the er and it said vital capacity cannot increase, it's just the tidal vol that increases

That's what I said.

"For TIDAL VOLUME to increase, X and Y will have to decrease."

 

[Soldier313]

Yes, that's how they are loaded at the source but the point is that the sources are the photosynthesising leaves, while the sinks are other parts of the plant, like the roots, storage organs. So, when the sugars are loaded into the sieve elements of the leaves, this means that there is more solute in the phloem sap. If you look at my answers above about solute potential is related to water potential, I have said solute potential is always negative, meaning more solute REDUCES/DECREASES water potential. The key here, to avoid confusion, is to understand that solute concentration is inversely proportional to water potential, and increasing it reduces water potential.

thanx, that really helped

 

[Soldier313]

It increases.

This is the part i am emphasizing on, the vital capacity cannot change

 

[stella123]

plz help me guys

 

[Nibz]

This is the part i am emphasizing on, the vital capacity cannot change

That was for Tidal Volume too.

 

[sarahnafea]

i replied but forgot to quote u perhaps my explanation helps?

just checked the er and it said vital capacity cannot increase, it's just the tidal vol that increases

 

[Soldier313]

During excercise tidal volume increases and this will decrease Inspiratory Reserve Volume (i.e. the volume of air which u could inhale but dont) - in this case, volume X. Same goes for volume Y. Thing of Reserve Volumes as a Bank of air. When u excercise u take loans of air from ur reserve and this loan is what increases ur tidal volume. Oh and thanks for ur reply up there

that really helped, jazakallah

 

[stella123]

ques 34 38 n 40 of nov 2010/13

 

[XPFMember]

aoa wr wb

need help with this plz

jazakAllah

 

[Ineedhelp]

can someone please answer my questionss
1) What to T killer and T helper cells do ?
2) does the loading of sucrose in the phloem seive tube require active transport? or massflow? :S

 

[XPFMember]

aoa

this one too....why wont it alter the active site shape?

 

[Soldier313]

urgent help for this one pleeeeeeeaaaaaseeeee

 

[sarahnafea]

If it's not too late does anybody understand the relationship between the girth (circumference) of a tree trunk and the cohesion-tension theory? It seems to be a recent favorite amongst the examiners. Thanks

 

[Nibz]

aoa

this one too....why wont it alter the active site shape?

View attachment 12860

Because it binds to the 'Enzyme-substrate' complex where the active site has already been occupied.

 

[Jaf]

help needed!!!!!! question 34, 38 and 40 of oct/nov/13/2010

34, fIrst you need to see that in sample 3, when uracil is 25, C is nil, which means C is THYMINE because the two are never found together. Once you have found that C is Thymine, whichever base is the same/nearly the same as C is adenine because, due to base pairing specificity, the two have to be equal. If you check, B is nearly the same as C in all cases and, so, the answer is B.

38, you may check above. I asked the same question on he last page, as 39 on paper 11, check the answer provided for that.

40, for this you need to understand basic mathematics. By mutipling the number of individuals with the biomass per individual, you will get the total biomass of the species in the ecosystem. When you multiply this by the energy per unit mass, you get the oral energy held by that species in the whOle foodchain. So,

Energy = number * mass per unit * energy per unit mass

Do that for Ll if them and you get:

P = 1000
Q = 100
R = 1.8
S = 450 000

In pyramids of energy, the species with most energy is at the base and those with the least are at the top. So, according to this, S should be at the base, followed by P and Q, and R at the top. This is only found in B so that's the answer.

 

[Soldier313]

If it's not too late does anybody understand the relationship between the girth (circumference) of a tree trunk and the cohesion-tension theory? It seems to be a recent favorite amongst the examiners. Thanks

i think the circumference decreases as the cohesion-tension forces decreases

 

[sarahnafea]

it binds to the allosteric site ! the active site is too busy spending quality time with its substrate

aoa

this one too....why wont it alter the active site shape?

View attachment 12860

ric

aoa

this one too....why wont it alter the active site shape?

View attachment 12860

s

 

[sarahnafea]

urgent help for this one pleeeeeeeaaaaaseeeeeView attachment 12861

to say i fully comprehend this question would be an overstatement but what i can tell u is that u pretty much get it by elimination. the other choices sound absurs. antibodies are SPECIFIC to one antigen ! so an antibody complementary to antigen X will never stimulate an immune response to Y. that's pretty much what mr.examiner is trying to say by this seemingly complicated (but really not) question

 

[Soldier313]

to say i fully comprehend this question would be an overstatement but what i can tell u is that u pretty much get it by elimination. the other choices sound absurs. antibodies are SPECIFIC to one antigen ! so an antibody complementary to antigen X will never stimulate an immune response to Y. that's pretty much what mr.examiner is trying to say by this seemingly complicated (but really not) question

yea i guess elimination would be the only way....thanx fr yr help

 

[XPFMember]

aoa

these 2 questions plz...