A level Biology: Post your doubts here!

[RoOkaYya G]

"
using proportional dilution, by adding a unit volume of a solution of a known concentration to a
solvent to obtain the required concentration, e.g. to dilute a stock solution by 5, 1 cm3 of the stock
solution is added to 4 cm3 of solvent. This gives a 1:5 dilution. To make a standard volume of a specific
concentration a formula V1C1 = V2C2 can be used. V1 is the volume of the stock solution, C1 the
concentration of the stock solution and V2 is the volume of the required solution, C2 is the concentration
of the required solution, e.g. a stock solution contains 100 mg cm–3 (C1) and need to make 10 cm3
(V2) of a solution with a concentration of 25 mg cm–3 (C2). The volume of stock solution needed is
V1 = 10 cm3 (V2) × 25 mg cm–3 (C2) / 100 mg cm–3 (C1). Cancelling units, V1 = 100 cm3 (V2) × 25 (C2) / 100
(C1) = 2.5 cm3"

I found this in our Biology syllabus. But I need more information about it.

http://abacus.bates.edu/~ganderso/biology/resources/dilutions.html
http://bio.classes.ucsc.edu/bio20L/MANUAL/Lab 1.pdf

view these sites

 

[DeViL gURl B)]

Could I please get NOTES On the AL LEVEL CHAPTERS .. the detailed notes .. PLEASE!
IF anyone knows please help me .. Especially the chapter "regulation and Cantrol"
Please give for all the chapters.
Thank you

 

[maryam fatima]

Could I please get NOTES On the AL LEVEL CHAPTERS .. the detailed notes .. PLEASE!
IF anyone knows please help me .. Especially the chapter "regulation and Cantrol"
Please give for all the chapters.
Thank you

http://www.s-cool.co.uk/a-level/biology

 

[maryam fatima]

DeViL gURl B) this site is really good if u either wanna read whole chapters or just revise them

 

[Panda.lover :3]

hello so i needed experienced opinion for a decision i took ... i have decided to give 3 composites in coming may June session chemistry, physics and biology (Alevel) so is it possible? fyi i am also giving maths A2 :/

 

[Syed Fakhar Hussain]

Can Anybody plz upload a compiled topical Biology MCQ's softcopy?

 

[♣♠ Magnanimous ♣♠]

Can Anybody plz upload a compiled topical Biology MCQ's softcopy?

https://www.xtremepapers.com/community/threads/as-biology-topicals-here.32685/

 

[♣♠ Magnanimous ♣♠]

Can Anybody plz upload a compiled topical Biology MCQ's softcopy?

https://www.xtremepapers.com/community/threads/as-level-biology-topical-questions.32984/#post-857839

 

[oahmed64]

Guys,please,Im extremely confused in the nervous system.In my notes,it says that energy from stimulus causes the voltage gated channels to open but in other notes it says that action potential from the RECEPTOR (which converted the stimuli into energy) to open.So in a nutshell,what causes the voltage gated channels to open ?

 

[princessnoor]

Can anyone plz tell me where can I get A2 biology notes?

 

[princessnoor]

Guys,please,Im extremely confused in the nervous system.In my notes,it says that energy from stimulus causes the voltage gated channels to open but in other notes it says that action potential from the RECEPTOR (which converted the stimuli into energy) to open.So in a nutshell,what causes the voltage gated channels to open ?

Voltage gated Chanel open when neurotransmitter binds to their receptor proteins and their shape is altered so allowing Na ions to pass through.
I hope I'm right

 

[Wolfgangs]

So guys, I need your advice in something. I'm seeking for A in my A levels. I currently have c in my AS levels. So, do you think I can still score A somehow?

 

[Hanona]

So guys, I need your advice in something. I'm seeking for A in my A levels. I currently have c in my AS levels. So, do you think I can still score A somehow?

you can i guess but only if you get full marks in both a2 papers

 

[Awesome12]

http://papers.xtremepapers.com/CIE/...and AS Level/Biology (9700)/9700_w03_qp_1.pdf

Question 3? The golgi apparatus usually makes enzymes. Why is the answer C?

 

[huh]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_w03_qp_1.pdf

Question 3? The golgi apparatus usually makes enzymes. Why is the answer C?

Look up exocytosis. Golgi helps enzymes undergo exocytosis.

 

[Saurabh Raperia]

Can somebody help me with the list of lab experiments which one needs to sit in the practical skills paper 3!!?

 

[slisjunknown]

http://papers.xtremepapers.com/CIE/...nd AS Level/Biology (9700)/9700_s13_qp_13.pdf
Question no 4...please reply asap; got an exam day after

 

[slisjunknown]

and question 14 of the same paper...

 

[rexsun]

Hello everybody. I have been confused by the following question for a long time...Please help
The answer for this question is D.
But why can't C be right? I thought that stomata are open because of guard cells but not transpiration.

 

[RoOkaYya G]

Hello everybody. I have been confused by the following question for a long time...Please help
The answer for this question is D.
But why can't C be right? I thought that stomata are open because of guard cells but not transpiration.
View attachment 49685

stomata is the opening (the hole) ....guard cells(the inner wall) contract n expand so tht stomata is open or close

loss of water potential maintains the water potential yes but in some conditions only..it maintains it only whn theres a net movement....like theres an excess of water vapour..so its being loss to maintain the correct proportion....but here best answer is D....thts the main reason....so its D