A level Biology: Post your doubts here!

[My Name]

Answer is C. Because of the fact that when memory cells are persent when second time pathogen enters they are activated and thus more concentration of Antibodies?

Can anyone answer this!
Please and Thank you!

 

[My Name]

The answer is D.
Why not B? Is it only for the reason that Malaria is mostly transmitted by Female Anopheles mosquito?

 

[qwertypoiu]

View attachment 52883
Answer is C. Because of the fact that when memory cells are persent when second time pathogen enters they are activated and thus more concentration of Antibodies?

Can anyone answer this!
Please and Thank you!

Y is obviously primary, and X secondary, since Y takes longer time to produce antibodies, and makes less of it.
So that limits it to C and D.
During primary response, memory cells were produced by both B-cells and T-cells.
However, for the concentration of antibodies to increase, it's the B-cells that that must have cloned rapidly to develop into plasma cells that produce antibodies. So C.

(Technically, even T-cells could indirectly cause this, since T-helper cells secrete cytokines that stimulate B-cells to develop into plasma cells and produce antibodies, but I guess this is indirect and would take longer time)

 

[qwertypoiu]

View attachment 52884
The answer is D.
Why not B? Is it only for the reason that Malaria is mostly transmitted by Female Anopheles mosquito?

I think you made a mistake in saying the answer is D.
Answer should be A.
B is definitely wrong, HIV cannot be transmitted through airborne droplets.
D is definitely wrong, TB is caused by a bacterium not virus.
Both A and C seem correct to me, however the main method of transmission for malaria is through the vector female Anopheles mosquito, as you said, so A is the best option.

 

[My Name]

I think you made a mistake in saying the answer is D.
Answer should be A.
B is definitely wrong, HIV cannot be transmitted through airborne droplets.
D is definitely wrong, TB is caused by a bacterium not virus.
Both A and C seem correct to me, however the main method of transmission for malaria is through the vector female Anopheles mosquito, as you said, so A is the best option.

Yes,sorry I meant to write A.
Ty

 

[Sadi66]

What is frameshift mutation?
Pls explain

 

[Wolfgangs]

Can someone please explain this question?

 

[qwertypoiu]

Can someone please explain this question?

On the picture you can see:
40 divisions of eyepiece graticule = 0.1mm
1 division = 0.1mm/40 = 0.0025mm

It is also clear that the radius of vision is 50 divisions:
50 divisions = 0.0025mm x 50 = 0.125mm

Since the answers are in micrometers let's convert it now:
0.125mm = 125 micrometers.

Area = pi*r^2 = 3.14159265358979... x 125 x 125 = 4.9 x 10^4 micrometer squared

C

 

[Farhad221]

Question 27
http://maxpapers.com/syllabus-materials/biology-9700/attachment/9700_w14_qp_13/

 

[princess Anu]

should be D because in a resting muscle there is a lower proportion of CO2 therefore curve is towards the left( indicating higher affinity of Haemoglobin for O2) plus it should be lower bcz the parial pressure of O2 has to be low becz resting muscle respires too..using up O2

Question 27
http://maxpapers.com/syllabus-materials/biology-9700/attachment/9700_w14_qp_13/

 

[Sadi66]

what does key time means ?

 

[Laila39]

Aoa
Can someone PLEASEE explain to me the process of semi-conservative replication of DNA through the N14/N15 experiment like I know how replication occurs but Im not able to do the mcqs with this stuff.. I need to know the list of outcomes after each generation so if someone could please list out the results after each generation.. thankss guyss!

 

[princess Anu]

Is Glucose a macromolecule?

 

[fantastic girl]

Is Glucose a macromolecule?

No its not
its a simple monosaccharides

 

[fantastic girl]

http://onlineexamhelp.com/wp-content/uploads/2014/02/9700_w13_qp_13.pdf
Can someone explain Q23
nd 24 - why wud sugar move out ? :S

 

[Farhad221]

http://onlineexamhelp.com/wp-content/uploads/2014/02/9700_w13_qp_13.pdf
Can someone explain Q23
nd 24 - why wud sugar move out ? :S

24 sugar will move out due to energy required by the growing cells for protein sythesis and Q 23 is the answerD

 

[fantastic girl]

24 sugar will move out due to energy required by the growing cells for protein sythesis and Q 23 is the answerD

isnt it like roots are well growing part so they need more energy ?
23 is D...but y ? :/

 

[Farhad221]

isnt it like roots are well growing part so they need more energy ?
23 is D...but y ? :/

yes as they are growing they require energy for replication of dna and protien synthesis.
23 is D because lingin strengthen the xylem vessels so they wont collapse under hydrostatic pressure which in this case is due to high rate of transpiration.

 

[Laila39]

Can someone explain to me the effect of carbon dioxide on haemoglobin?

 

[Farhad221]

Can someone explain to me the effect of carbon dioxide on haemoglobin?

it decreases the haemoglobin(HB) affinity for oxygen, This is known as the BOHR EFFECT. Why does this happen well in water CO2 molecules from carbonic acid H2CO3 which dissociates to form H+ and HCO3 - ions. This is catalysed by the enzyme carbonic anhydrase. H+ ions then react with HB to form HHB hence releasing the oxygen molecules HB was bidden to. This helps to release more oxygen in active muscles. I