AS Biology P1 MCQs Preparation Thread

[confused123]

unsaturated fatty acids give fluidity to the membrane helping in movement of substances in and out of the membrane , C looks right as well bcz increase in proteins will aid in production of more exocytic vesicles......

aoa

why so?

View attachment 12752

to the membrane

 

[Peter Check]

HELP! How do i do this?? What exactly is net primary productivity??

 

[Soldier313]

Permeability is whether a substance is ALLOWED TO ENTER OR EXIT through a membrane. Since Cell wall is FULLY permeable( OL biology ) it allows ANYTHING TO PASS THROUGH IT. Whereas a cell membrane is PARTIALLY PERMEABLE which means of selective substances can enter and leave cell through it. I dont know anything COMPLETELY UNPERMEABLE but it means nothing can move across it ( like lignin i think ).

Free Entry is when something is ALLOWED to passed through a membrane.

Water is always allowed to enter or leave cell so cell wall is allows water to move across it and cell membrane also allows water to move across it.

thanx bro

 

[JulyMei]

What is the difference between sunken stomata and stomata located in the grooves?

 

[Just M]

w11_12 Q40. Why is it D?

In water-logged areas, there will be less amount of O2. Hence, this will contribute to anaerobic condition. Denitrifying bacteria lives well in anaerobic conditions. So, process of denitrification will increase (Y)

 

[Peter Check]

A pyramid of energy shows the energy of an organism in a trophic level. So to get that, you should multiply the biomass of one individual by the number of individuals (to get the total biomass)
The results are:
P: 1000
Q: 50
R: 1
S: 900000

Arrange them in a pyramid, and you'll find out that the answer is B

thnx a tonne

 

[Soldier313]

HELP! How do i do this?? What exactly is net primary productivity??View attachment 12754

net primary productivity = gross productivity - energy lost in respiration
gross productivity = total light energy - light reflected

 

[Nibz]

What is the difference between sunken stomata and stomata located in the grooves?

Both reduce transpiration, I think. And you only need to know this.

 

[Just M]

Aoa wr wb!

Why not 2?

View attachment 12746

The question is trying to troll us. Always remember, the colour changes from blue - green - yellow - brown - brick-red.

 

[Irfan1995]

The question is trying to troll us. Always remember, the colour changes from blue - green - yellow - brown - brick-red.

Technically, it can't just go from orange to green. So 2 is definitely out.

 

[Just M]

aoa

why so?

View attachment 12752

When it's getting colder, the membrane will be less fluid. Since unsaturated bonds are less saturated, i think they'll contribute to the fluid-ness of the membrane. Erm, how about cholesterol then ?? They also maintain the fluidity of the membrane right ?? What is the difference between the role of hydrocarbon chains and cholesterol ?? I'm always stucked at this part

 

[Peter Check]

net primary productivity = gross productivity - energy lost in respiration
gross productivity = total light energy - light reflected

thank you

 

[Irfan1995]

When it's getting colder, the membrane will be less fluid. Since unsaturated bonds are less saturated, i think they'll contribute to the fluid-ness of the membrane. Erm, how about cholesterol then ?? They also maintain the fluidity of the membrane right ?? What is the difference between the role of hydrocarbon chains and cholesterol ?? I'm always stucked at this part

From what I learnt in AP Biology, cholesterol is responsible for maintaining the fluidity of the membrane. Unsaturated tails just increase the fluidity. At high temperatures, the membrane is too fluid, so cholesterol stiffens the membrane, but at low temperatures, the membrane is too stiff, so the cholesterol molecules loosens them up a bit.

 

[Soldier313]

Please can someone help
^why is it C and not D?


^why is it B and not C?


^ why is it A and not B?

 

[Irfan1995]

Please can someone helpView attachment 12755View attachment 12756View attachment 12757

1) Male bees are haploid, so they are NOT genetically identical. They are formed from diploid cells which have gone through independent assortment and crossing over to increase variation. Haploid cells produce other haploid cells by mitosis, not meiosis. If they were produced by meiosis, the 1n chromosomes would be reduced to half-n which is not possible.

2) Lets check each possibility:
A) You have no way of knowing that
B) This is a true statement because the rate of increase in concentration is high and constant, so there must be a continuous supply of substrate molecules
C) Actually, it is a maximum, not low.
D) Since there are many substrate molecules, more enzymes means that more substrate molecules can be broken down faster.

3) We know that 1% of sunlight energy is used in photosynthesis. So W = 1
10% of the energy is passed on the next trophic level, but as at higher trophic levels, the efficiency increases, so X = 10, Y = 20
What's left is given to decomposers.

 

[sophiaaa]

1) Male bees are haploid, so they are NOT genetically identical. They are formed from diploid cells which have gone through independent assortment and crossing over to increase variation. Haploid cells produce other haploid cells by mitosis, not meiosis. If they were produced by meiosis, the 1n chromosomes would be reduced to half-n which is not possible.

2) Lets check each possibility:
A) You have no way of knowing that
B) This is a true statement because the rate of increase in concentration is high and constant, so there must be a continuous supply of substrate molecules
C) Actually, it is a maximum, not low.
D) Since there are many substrate molecules, more enzymes means that more substrate molecules can be broken down faster.

3) We know that 1% of sunlight energy is used in photosynthesis. So W = 1
10% of the energy is passed on the next trophic level, but as at higher trophic levels, the efficiency increases, so X = 10, Y = 20
What's left is given to decomposers.

hey..for question no.3 what do u mean.didin't get it clearly.plz xplain once again.how does efficiency increases at high levels....?????

 

[confused123]

during transcription only once sugar phosphate backbone is build when mRNA is constructed. it forms only once.

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s11_qp_11.pdf
Q22 the answer according to the mark scheme is A....
why not D, i agree with the 1 and 2 but 3...sugar and phosphate bonds, do form...when the free mRNA nucleotides in the nucleus come and attach to the exposed template (a DNA strand) something forms the sugar phosphate backbone...so the sugar phosphate bonds are forming between the mRNA nucleotides...
4 even this seems true.....the free mRNA nuclotides in the nucleus come and pair with the exposed DNA strand according to compleentary base pairing rules....
so why A?

 

[DARK DRAGON]

http://www.xtremepapers.com/papers/...and AS Level/Biology (9700)/9700_w03_qp_1.pdf
Q7 plz explain answer is D

 

[Soldier313]

1) Male bees are haploid, so they are NOT genetically identical. They are formed from diploid cells which have gone through independent assortment and crossing over to increase variation. Haploid cells produce other haploid cells by mitosis, not meiosis. If they were produced by meiosis, the 1n chromosomes would be reduced to half-n which is not possible.

2) Lets check each possibility:
A) You have no way of knowing that
B) This is a true statement because the rate of increase in concentration is high and constant, so there must be a continuous supply of substrate molecules
C) Actually, it is a maximum, not low.
D) Since there are many substrate molecules, more enzymes means that more substrate molecules can be broken down faster.

3) We know that 1% of sunlight energy is used in photosynthesis. So W = 1
10% of the energy is passed on the next trophic level, but as at higher trophic levels, the efficiency increases, so X = 10, Y = 20
What's left is given to decomposers.

thanx a lot that really helped

 

[Just M]

Hi. Why does spiralisation and condensation of DNA happen during prophase ?? Why isn't it interphase ??