A level Biology: Post your doubts here!

[zahra azam]

s2010

Paper 1?

 

[zahra azam]

and i am not humpty fgs

Even i am not zarra

 

[HumptyR]

Paper 1?

zahir si baat ha :s

Even i am not zarra

OTAY zarra u r not zarra. is it fine now zarha

 

[zahra azam]

zahir si baat ha :s

OTAY zarra u r not zarra. is it fine now zarha

I do edexcel bachey....that is why i asked

Much better -_- thanks

 

[HumptyR]

I do edexcel bachey....that is why i asked

Much better -_- thanks

Oh Oh kay mujhe pata ni tha zarra aunty

Nope Nope pleasure is all mine

 

[zahra azam]

Guys is there any unit of basal metabolic rate?

 

[HumptyR]

Guys is there any unit of basal metabolic rate?

calories/day i guess

 

[Lola_sweet]

Guys is there any unit of basal metabolic rate?

calories/day

 

[zahra azam]

Thanks guys
N for EAR?

 

[slisjunknown]

Can someone please tell me why the answer is C?

 

[Sariya Khan]

View attachment 59128
Can someone please tell me why the answer is C?

The width of a cell membrane is 7nm.. that's the reason why we use electron microscope to see it clearly. The white blood cells diameter can't be in mm.. if it were so, we would not need a microscope to view them . As for the alveoli their diameter too is in micrometers since we need a large surface area to volume ratio for quick diffusion across the alveolar walls.. You must have read that the smaller the surface area, the larger surface area to volume ratio. Hope this makes sense

 

[slisjunknown]

The width of a cell membrane is 7nm.. that's the reason why we use electron microscope to see it clearly. The white blood cells diameter can't be in mm.. if it were so, we would not need a microscope to view them . As for the alveoli their diameter too is in micrometers since we need a large surface area to volume ratio for quick diffusion across the alveolar walls.. You must have read that the smaller the surface area, the larger surface area to volume ratio. Hope this makes sense

Thanks, but they are asking about the cell wall(which is not 7nm)...and I didn't get the rest

 

[Sariya Khan]

Thanks, but they are asking about the cell wall(which is not 7nm)...and I didn't get the rest

The diameter of cell walls in different organisms is not the same.. for example in prokaryotes it's diameter ranges from 5 to 80 nm and in eukaryotes it's about 1000 to 5000 nm thick. (I actually searched for it).. What did not you get dear? Can you please specify?

 

[Sariya Khan]

Thanks, but they are asking about the cell wall(which is not 7nm)...and I didn't get the rest

The average diameter of a eukaryotic cell is about 50 micrometers!

 

[Rizwan Javed]

View attachment 59128
Can someone please tell me why the answer is C?

Look, all the structures mentioned here in the MCQ can never be in mm because if they were in mm, you would have been able to see them with naked eye, but you aren't able to do so. So just eliminate all the options which quote 'mm' as the measuring unit. After elimination you'll notice that you're left with only option C.

Actually according to syllabus you're not expected to memorize the sizes of these. So you're to compare the structures mentioned and then deduce. Cell walls are obviously smaller than white blood cells or alveoli. So if you're measuring WBCs in micromemter, then cellwalls must be in nm. So you're to solve this by comparisons.

 

[Lola_sweet]

View attachment 59128
Can someone please tell me why the answer is C?

even if you dnt knw the exact length
we know that nothing can be measured in mm otherwise it can be seen with the naked eye
so cross off any option with mm

 

[slisjunknown]

THANKS A LOT...I got it

 

[help pls]

View attachment 59097

C is correct i think not sure,because A,B and D are wrong as we cannot see ribosome,Mitochondria and
Lysosome under light microscope.

 

[demon29]

http://biologystudynotes.blogspot.com/2016/02/cell-membrane-and-transport.html i will be posting more topics soon.

 

[shingiechingz@8]

guys what is the function of the glycocalyx