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A level Biology: Post your doubts here!

not.maria

not.maria

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Gehad Mohamed said:
Hello! Can someone please explain why ans 5 b ii is not about enzyme activity with pH instead of collision with substrate
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s11_ms_22.pdf
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s11_qp_22.pdf
Click to expand...
it is about both the mark scheme says
"ref. presence of hydrogen ions, partial denaturation (less steep) / denaturation (plateau);"

this means that the enzymes structure is affected by change in ph so that it does not work fully.
Also as the number of substrate molecules will decrease over time the number of collisions with the enzyme would decrease and the rate of reaction would decrease
i hope that clears it up
 
Gehad Mohamed

Gehad Mohamed

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not.maria said:
it is about both the mark scheme says
"ref. presence of hydrogen ions, partial denaturation (less steep) / denaturation (plateau);"

this means that the enzymes structure is affected by change in ph so that it does not work fully.
Also as the number of substrate molecules will decrease over time the number of collisions with the enzyme would decrease and the rate of reaction would decrease
i hope that clears it up
Click to expand...
Yes clear thnx alot
 
ZaqZainab

ZaqZainab

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Alazne Diamond

Alazne Diamond

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not.maria said:
View attachment 36770
in the question:-
"State three features of the leaf, visible in Fig. 3.1, which show that it has developed in
a sunny position."
the markscjeme mentions
>smaller air spaces
>thick leaf

I dont understand how smaller air spaces are an adaptive feature.
Nor do I undertsnad how we are supposed to know if the leaf is thick or thin because for me 450micrometres in THIN.

Can anyone please explain?

THANKS!
Click to expand...
sunny position means high temperature n hence transpiration rate is more.......if ther would be larger air space then it wil b easy for water to evaporate.....so to reduce loss of water air space iz small.........n m nt sure abt the thickness
 
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Mohammed salik

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@
ZaqZainab

Gehad Mohamed said:
Hi !! Can someone please explain why in Q 2 F is partially permeable and G is fully permeable , shouldn't it be reverse as the outer on is always the cell wall !!
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s12_qp_21.pdf
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s12_ms_21.pdf
Click to expand...

Cell walls Is Not F and It is Never Partially Permeable!
F is cell Membrane Which is Partially Permeable Phos-pholipid Bilayer
G is Cell Wall which is completely Permeable Because of Gaps between Cellulose Fibers, hence allows free Movement Of Water or other substances!
Hope That answers Your Question! :)
 
ZaqZainab

ZaqZainab

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Mohammed salik said:
@
ZaqZainab



Cell walls Is Not F and It is Never Partially Permeable!
F is cell Membrane Which is Partially Permeable Phos-pholipid Bilayer
G is Cell Wall which is completely Permeable Because of Gaps between Cellulose Fibers, hence allows free Movement Of Water or other substances!
Hope That answers Your Question! :)
Click to expand...
Cell walls are semi permeable
btw isn't the cell wall always the one on the outside? <--that's what my teacher has taught me
 
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6Astarstudent

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MÁťT PŭמҚ said:
can u explain in more detail abt electron transport chain?
Click to expand...
Reduced NAD/FAD passed to ETC, where they released the hydrogen (which gets split into H+ and e-).
The electrons are passed through a series of e- carriers down energy gradient in the inter-membrane space.
Energy released from this is used to move H+ from matrix to inter-membrane space.
The protons builds up a concentration gradient, so the protons pass back to the matrix through ATP synthase.
The proton motive force (electrical potential energy) synthesizes ATP from ADP + Pi (This is chemiosmosis)
Lastly in the matrix, H+ and e- combine with O2 to form H2O.
 
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Mohammed salik

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ZaqZainab said:
Cell walls are semi permeable
btw isn't the cell wall always the one on the outside? <--that's what my teacher has taught me
Click to expand...
You Could rephrase Your Sentence to :- The first membrane or (the membrane closest) to Cell organelles is Cell membrane and Second one is Cell wall. If we talk about this Electron Micro-graph Of two Adjacent cells.
If You look Closely The first Membrane to organelles is F so that is Cell Membrane And second one is G which is cell wall!
Hope that Answers You Question! :)
 
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