AS LEVEL BIOLOGY... discuss here AS students only :)

[HubbaBubba]

In one paper they asked us for the structure n explanation of xylem so they had mentioned large diameter so more water can pass....
Wat r we supposed to write!

1. Large lumen - Allows a large volume of water to be transported at once
2. The walls are coated with lignin to make it water proof and also prevent the structure from collapsing
3. No cell contents so lumen is able to transport large volume of water with little resistance
4. End walls are broken down, allowing a continuous flow of water
5. There are pits to allow lateral movement of water

that's all I can think of

 

[daredevil]

Yea man easy papers along with extreme low thresholds!

hahha thats a little wishful don't u think
i jst wish we all get As and thats it! to hell with the gt and the paper

 

[ruler_of_the_world]

Thanks but I was jus confirming about the size of lumen cause somewhere they mentioned small n someplace they mentioned large. Anyways I got it thanks

 

[ruler_of_the_world]

Lol so to get As we do need a low threshold u know cause their marking gets pretty strict too sometimes

 

[daredevil]

Lol so to get As we do need a low threshold u know cause their marking gets pretty strict too sometimes

true that -_-

 

[goodluckayesha]

can sm1 plz tell wht r phosphodiester bonds

 

[daredevil]

can sm1 plz tell wht r photodiester bonds

photodiester?? r u sure u got the spellings ryt??
i know about phosphodiester but never heard of photodiester

 

[goodluckayesha]

photodiester?? r u sure u got the spellings ryt??
i know about phosphodiester but never heard of photodiester

yh srry I mean phosphodiester wht is it??

 

[daredevil]

yh srry I mean phosphodiester wht is it??

in AS we are not exactly required to know the actual bonding and stuff but from the name u can gather that there is a -C-O-C- bond and a phosphate group in what ever the molecule is and thats all u need to know i think.
but just for the sake of it here's a bit of an explanation u see this bonding links the nucleotides together. the nucleotides have a phosphate group at on end and an OH group on a C on the lower end. the phosphate of one nucleotide on the upper side binds with the OH of a second nuclrotide on the lower end with the release of a H2O molecule and form an ester bond as they link up. thus the phosphodiester linkage... if u don't get the idea then get back to me and ill explain it further

 

[daredevil]

yh srry I mean phosphodiester wht is it??

i hope u get a better idea with this

 

[goodluckayesha]

in AS we are not exactly required to know the actual bonding and stuff but from the name u can gather that there is a -C-O-C- bond and a phosphate group in what ever the molecule is and thats all u need to know i think.
but just for the sake of it here's a bit of an explanation u see this bonding links the nucleotides together. the nucleotides have a phosphate group at on end and an OH group on a C on the lower end. the phosphate of one nucleotide on the upper side binds with the OH of a second nuclrotide on the lower end with the release of a H2O molecule and form an ester bond as they link up. thus the phosphodiester linkage... if u don't get the idea then get back to me and ill explain it further

thnq so much I get it now

 

[PANDA-]

Actually, in one paper, I felt like I was doing Chemistry, they asked to draw two amino acids bonded together in a peptide bond, and describe the peptide bond, and also they asked about the phosphodiester bond.

On a side note, does anyone have any problems with those "With reference to Figure... blah blah blah" questions?

 

[daredevil]

thnq so much I get it now

anytime

 

[deane26]

Suggest why the rate of water movement in an intact shoot is less than that measured in
the potometer.

 

[daredevil]

Suggest why the rate of water movement in an intact shoot is less than that measured in
the potometer.

umm i dont think i understand the question.... the rate of water movement is slow?? as in less water is moving than what is recorded by the potometer as being lost??

 

[PANDA-]

Suggest why the rate of water movement in an intact shoot is less than that measured in
the potometer.

I'm gonna guess that you meant transpiration by "water movement"
The potometer measures the rate of water uptake, not the rate of transpiration, and not all the water that the plant takes up is transpired. Some of the water is used in photosynthesis, some to maintain the turgidity of cells, so the rate of transpiraton is less than that measured by the potometer.

 

[deane26]

umm i dont think i understand the question.... the rate of water movement is slow?? as in less water is moving than what is recorded by the potometer as being lost??

Its m/j 04 question. I dont get it why the answer mentioned abt casparian strips etc

 

[daredevil]

Its m/j 04 question. I dont get it why the answer mentioned abt casparian strips etc

u didn't give me the whole question
ok the difference bases on the fact that potometer measures for the small part of the plant i.e. the shoot. however actually before cutting the shoot the plant was in its natural habitat and in its natural form. that means the root need to take up what limited amount of water is available in the soil. and casparian strips do what? they actually provide a barrier to the water travelling up the xylem so that it cant travel through apoplast and has to go through the cytoplasm which takes longer. in the shoot the water directly enters the xylem without having to face the casparian strip.

just keep in mind that they are asking about the difference of water movement rates in a cut out shoot and a natural plant with the roots attactched and u'll be okay

 

[Irfan1995]

Lol so to get As we do need a low threshold u know cause their marking gets pretty strict too sometimes

Not really, to get an A, you gotta get questions right. It's as simple as that. Don't count on the threshold.
If the threshold is low, then you can be sure that the exam was hard for the general population (which normally includes you as well) and that their marking is relatively strict.

 

[Moi]

As everyone said, herd immunity is vaccinating a large proportion of the population (ideally, 95%)
When most people are vaccinated, the disease can only be transferred within the unvaccinated population (5%)
Since the number of unvaccinated people are very low, the disease will eventually die since it can't pass on from person to person easily.

Thank youuuuu!!!