A level Biology: Post your doubts here!

[My Name]

u really r a great help !! may God bless u and u get straight A*s

Thank you ^_^ I'm glad I could help. Ameen
May God bless you with A*s as well!

 

[Jenn]

How do we do this?

 

[princess Anu]

is it C?

no d

 

[princess Anu]

yes can u explain why not B

WHTS THE ANS d?

 

[bubbles1997]

yes can u explain why not B

View attachment 53249
doesn't nitrogen fixation need anaerobic?? ... but it's A...

no, they need oxygen for working

 

[nehaoscar]

no, they need oxygen for working

that is very weird, I just double checked with CIE endorsed textbook 2013 third edition as well as the encyclopedia
nitrogen fixation in soil requires
supply of hydrogen, supply of ATP, anaerobic conditions

ONLY nitrogen fixation in the atmosphere which is caused by lightning which directly converts N2 to NO2/NO skipping NH3 requires aerobic condition.

 

[Heba A.Moety]

what are hydrolytic enzymes??
and yeah it is D

hydrolytic enz. catalyse the hydrolyses of macromolecules to their constitute monomers by catalysing the breakage of bonds between the monomer units eg.amylase catalyse the hydrolysis of starch to maltose by breaking the glycosidic bonds

 

[qwertypoiu]

why can't this be B? disulphide nd peptide???

Only peptide bonds... Because this is simply a dipeptide... The space is too tight for two adjacent cysteine molecules to form disulfide bond.
We need longer chains for such associations to occur.

 

[qwertypoiu]

help

93 seconds... Time is always to a whole number of seconds... Our hands are too inaccurate and our reaction times too slow for having decimal accuracy...

 

[Jenn]

All the options appear correct to me...

 

[qwertypoiu]

View attachment 53249
doesn't nitrogen fixation need anaerobic?? ... but it's A...

I've taken a guess at this before Here

 

[qwertypoiu]

How do we do this?

0.75 second = 1 beat
60 seconds = x beat.

x = 80

 

[Jenn]

0.75 second = 1 beat
60 seconds = x beat.

x = 80

The answer is 75...

 

[Heba A.Moety]

https://www.xtremepapers.com/community/attachments/11160221_10204517600243144_750592502_n-jpg.53218/
plz explain

hope this make things clear

 

[qwertypoiu]

All the options appear correct to me...

A i think

Because yes water moves through membranes everywhere, as a result of random motion.
And yes water moves into cell 1 by osmosis, since it has a low (-7 is lowest number there) water potential.
As for number 3, it is wrong, water DOES move in both directions, just that both rates are same and so overall there is no net movement, but water still moves in both directions.
As for number 4, water does move out but this doesn't necessarily always mean that plasmolysis has occured.

 

[qwertypoiu]

View attachment 53252
hope this make things clear

Wow amazing.
Good to see effort being put into answers

 

[Heba A.Moety]

that is very weird, I just double checked with CIE endorsed textbook 2013 third edition as well as the encyclopedia
nitrogen fixation in soil requires
supply of hydrogen, supply of ATP, anaerobic conditions

ONLY nitrogen fixation in the atmosphere which is caused by lightning which directly converts N2 to NO2/NO skipping NH3 requires aerobic condition.

well nitrogen fixing bacteria in root nodules need anaerobic conditions but this is achieved as the legumes mop up the oxygen in the soil this means they can grow in aerated soils but in anaerobic conditions however the nitrifying bacteria needs aerobic conditions and denitrifying bacteria can only grow in anaerobic conditions which needs to be maintained since they are found free in the soil

 

[Heba A.Moety]

Wow amazing.
Good to see effort being put into answers

well thanks
people here helped me a lot this year and the year before so i thought i should be of some use!

 

[princess Anu]

93 seconds... Time is always to a whole number of seconds... Our hands are too inaccurate and our reaction times too slow for having decimal accuracy...

but what if it was stopwatch? :s

 

[qwertypoiu]

How do we do this?

The answer is 75...

Hmmm are you sure?
Please check again I really think answer should be C