A level Biology: Post your doubts here!

[innovative_1]

6

Hmm what??.
1 base pair means A-T or C-G.A-T base pair have 2 hydrogen bonds and C-G base pair have 3 hydrogen bonds.

You want minimum number of hydrogen bonds?.So 700 base pairs into 2 (considering all base pairs are A-T)=1400.This answer is confirmed from the mark scheme..
And max 700 into 3 =2100

But in M/J/13/P13/q24 says it's B i.e 700

 

[potatocorn12]

6


But in M/J/13/P13/q24 says it's B i.e 700

700 is correct because look it says 700 nucleotides in a length of DNA,They didnt say that 700 nucleotides are present in one strand which concludes to the fact that we have total 350(700/2) nucleotides/bases in each strand.Now 350 will form 2 bonds either with A or T so 350*2=700
i hope you understood:')

 

[innovative_1]

700 is correct because look it says 700 nucleotides in a length of DNA,They didnt say that 700 nucleotides are present in one strand which concludes to the fact that we have total 350(700/2) nucleotides/bases in each strand.Now 350 will form 2 bonds either with A or T so 350*2=700
i hope you understood:')

Oh thank you so much i didn't focused my bad

 

[Hisham Khan]

700 is correct because look it says 700 nucleotides in a length of DNA,They didnt say that 700 nucleotides are present in one strand which concludes to the fact that we have total 350(700/2) nucleotides/bases in each strand.Now 350 will form 2 bonds either with A or T so 350*2=700
i hope you understood:')

They didn't write the correct question.They wrote 700 base pairs not 700 neucleotides.

If Its 700 base pairs then remember there will be min 1400 hydrogen bonds!

 

[A*****]

Shouldn't 1 be wrong?
Cilia are paralysed so their activity decreases...no?

 

[Hisham Khan]

Shouldn't 1 be wrong?
Cilia are paralysed so their activity decreases...no?

Cilia aren't paralysed during asthma attack.That happens because of tar during smoking.
Scar tissues doesen't mean cilia are paralysed btw.So,to remove excessive mucus ciliated cells have to increase their activity.
Btw you can pretty much get the answer without even understanding this fact as EXOCYTOSIS occurs in goblet cells to release mucuss ,so leading us to option C

 

[Kanekii]

Anyone has any notes for food tests, would be really appreciated and thanks

 

[Krypton36]

Anyone has any notes for food tests, would be really appreciated and thanks

http://biologystudynotes.blogspot.com/2016/02/food-tests.html

 

[hancy pandey]

Folks, any prediction for biology practical ?
Please help
p34 is going to have the yeast experiment.....Please give your opinions

 

[Kanekii]

I

Folks, any prediction for biology practical ?
Please help
p34 is going to have the yeast experiment.....Please give your opinions

It could also be onion epidermis since it did not come in p33

 

[hancy pandey]

I

It could also be onion epidermis since it did not come in p33

Thank you so much......any other tips and hints

 

[sushil bista]

what will be the thresold of biology 34?

 

[Hisham Khan]

Shouldn't 1 be wrong?
Cilia are paralysed so their activity decreases...no?

Pls help me with this q,I beg !!!!.I dont get any point.

 

[A*****]

Pls help me with this q,I beg !!!!.I dont get any point.
View attachment 63706

The upper curve is for resting muscle, as it has lower concen. of CO2 and due to Bohr effect, the lower one is for the active muscle
So statement 1 is correct...as the blood moves from the lungs to the resting muscle, the change in haemoglobin saturation is P-S.
Statement 2 is pretty obvious.
3 is wrong. It is not the amount REQUIRED, but is actually the amount of oxygen NOT ABSORBED by the tissue
P-Q represents the difference bw the saturation of haemoglobin in the lungs bw the two capillaries so 4 is wrong
Statement 5 simply makes no sense

 

[A*****]

what will be the thresold of biology 34?

I couldn't see the cells in the microscope

 

[Hisham Khan]

I couldn't see the cells in the microscope

wdym.Not at all or coudn't identify? lul.I warned you questions will be hard but you are pretty good in biology so don't worry

if not at all,its pretty useless now but to focus and everything in less then 30 sec just forward the stage micrometer to maximu pussisation by using coarse adjuster.The condenser should be max down by using condenser adjuster.then use into 4 objective lens first and slowly move stage to and fro until you get good focus and then use focus adjuster to fine tune your image. lol

 

[Hisham Khan]

22-24. (keeping previous years threshold in mind)
Definitely not higher than 24. I might be the only one but this was the harder than many years as both the questions were something that are not frequently tested.

I dont think it will be that low.Definetly 31-32 because in 2017 and march 2018,thresholds were somewhere there.

 

[A*****]

wdym.Not at all or coudn't identify? lul.I warned you questions will be hard but you are pretty good in biology so don't worry

if not at all,its pretty useless now but to focus and everything in less then 30 sec just forward the stage micrometer to maximu pussisation by using coarse adjuster.The condenser should be max down by using condenser adjuster.then use into 4 objective lens first and slowly move stage to and fro until you get good focus and then use focus adjuster to fine tune your image. lol

Idk what was wrong with it
at x10 it was a bit visible but at x40 I couldn't see anything
Anyways, the rest of the paper was quite easy I guess

 

[Hisham Khan]

Idk what was wrong with it
at x10 it was a bit visible but at x40 I couldn't see anything
Anyways, the rest of the paper was quite easy I guess

The microscope question also destroyed me upto some extent xD but rest paper 33 was pretty easy as well and inshallah lets hope for an A! .
Me:Mom I got a B in practicals!
Mom:Come here
Me:HERE FOR THE TREAT!
Mom:strangles me,

 

[cellular_automata]

Guys help me here plz

which statement is incorrect for mitotic cell division
a.DNA is replicated Semi conservatively during Mitosis
b.DNA is normally unchanged from one generation of cells to the next
c.the daughter cells have the potential to produce the same enzymes as the parent cell
d.the same quantity of DNA is distributed to the nuclei of two new cells

It's A because replication of DNA is during S phase of interphase. Interphase and mitosis are part of the cell cycle but interphase is not part of mitosis.