A level Biology: Post your doubts here!

[Idolfanatic95]

Please Describe the function of the endodermis in roots.

In plants, it is a thin layer of parenchyma found in roots, just outside the vascular bundle. It regulates water flow. It consists of a single-celled ring which forms a selective barrier between the outer cortex and the inner pericycle tissue. In the roots, the endodermis cells are impregnated with suberin; a waxy substance which is water resistant, to form distinctive Casparian strips and prevent movement of water via the apoplast pathway. Water carrying mineral salts can only enter the root through the interior of cells (the symplast) as opposed to passing between cells (the apoplast). This means that the plant can directly regulate what enters the root proper. The endodermis cells contain starch granules as energy store. Mineral ions are actively secreted into the xylem vessels to maintain root pressure.

Hope it helps.

 

[Idolfanatic95]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s06_qp_2.pdf
Q.5 c part. how is the curve after the addition of competitive inhibitor lower then the previous curve drawn. plz try it

In 5(c), thiourea acts as an inhibitor. Though it temporarily binds to the enzyme, it still manages to lower the reaction rate. substrate molecules are still broken down but will take a longer span of time. Hence, the curve should be lower than the original one beacuse, thiourea will inhibit the reaction to some extent.

 

[Idolfanatic95]

hi all, please tell me that what happens to a chromosome between the end of anaphase and the start of the next mitosis.

Chromatids move to opposite poles and are pulled by the spindle fibres (centromeres being attracted first). Nuclear envelope and nucleolus reforms. When the chromatids have reached the poles of the spindle, they'll uncoil to form chromatin (making themselves less thicker). Cytokinesis occurs in which the cytoplasm constricts from the edges of the cell to divide into two. After this You can mention about what happens during interphase. Centrioles will replicate. and DNA replication takes place.

Hope that helps.

 

[Idolfanatic95]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s06_qp_2.pdf
question number 4 a part. how is the magnification 30,000. i mean the width is around 12 cm, so in micrometers it will be 120000 right? divided by 0.5 um. gives 240,000 X .

tell me one thing that 1 cm = 1 into 10000, is this conversion correct?

I think wht they've done here is, that they measured just the small bracket line where it's written o.5 micrometers. that comes like 1.4cm=1.4 x 10,000= 14 micrometers/0.5 gives us x 28000.
If you've noticed in all marking schemes, the measurement given are little larger than the ones we have been calculating so if there's a small difference like the one calculated above, it's okay. the measurements vary 'cause of the printing variations.

 

[Idolfanatic95]

In plants, it is a thin layer of parenchyma found in roots, just outside the vascular bundle. It regulates water flow. It consists of a single-celled ring which forms a selective barrier between the outer cortex and the inner pericycle tissue. In the roots, the endodermis cells are impregnated with suberin; a waxy substance which is water resistant, to form distinctive Casparian strips and prevent movement of water via the apoplast pathway. Water carrying mineral salts can only enter the root through the interior of cells (the symplast) as opposed to passing between cells (the apoplast). This means that the plant can directly regulate what enters the root proper. The endodermis cells contain starch granules as energy store. Mineral ions are actively secreted into the xylem vessels to maintain root pressure.

Hope it helps.

http://en.wikipedia.org/wiki/Endodermis#Function_of_the_Endodermis

 

[smartangel]

okay i just have a small confusion regarding Section B. my answers are really short. they do cover all the points in the marking scheme but are hardly half a page. specially the 8 mark question. is it okay? also.. the ms has short points. are they sufficient enough to gain full marks or do we have to elaborate on them?

 

[Idolfanatic95]

okay i just have a small confusion regarding Section B. my answers are really short. they do cover all the points in the marking scheme but are hardly half a page. specially the 8 mark question. is it okay? also.. the ms has short points. are they sufficient enough to gain full marks or do we have to elaborate on them?

U need not to go for the length much as long as all the required points are covered. marking schemes give a very brief "hint" about the points which are needed. therefore u need to elaborate a bit of each point. im sure it wud get you more than half a page

 

[confused123]

I think wht they've done here is, that they measured just the small bracket line where it's written o.5 micrometers. that comes like 1.4cm=1.4 x 10,000= 14 micrometers/0.5 gives us x 28000.
If you've noticed in all marking schemes, the measurement given are little larger than the ones we have been calculating so if there's a small difference like the one calculated above, it's okay. the measurements vary 'cause of the printing variations.

Thankyou sooo much idolfanatic, that really helped, i had lost the hope of getting any help here but you did it

 

[Idolfanatic95]

Thankyou sooo much idolfanatic, that really helped, i had lost the hope of getting any help here but you did it

No worries

 

[confused123]

what to do about the plan diagram? i mean can you tell me the important diagrams figures of which structure or plan diagrams we can remember. if there is any website where the plan diagrams are shown then it will be really helpful.
Thanks

 

[Idolfanatic95]

Some repeated figures include plant root, leaf and stem & Artery, vein or capillary shud be considered here as well. Im myself not so good with plan diagrams but these links might help you out:

https://www.facebook.com/video.php?v=435286225735

http://mrskingsbioweb.com/AICE Biology/Plan_diagrams_and_high_power_drawings.pdf
http://hhsibbio09.wikispaces.com/message/view/Topic+9+-+Plants/18140315?o=20#18792997
http://click4biology.info/c4b/9/plant9.1.htm
http://sweetibnotes.blogspot.com/2011/07/topic-9-plant-science.html
Vein and artery are quite simple to make though.

 

[confused123]

Some repeated figures include plant root, leaf and stem & Artery, vein or capillary shud be considered here as well. Im myself not so good with plan diagrams but these links might help you out:

https://www.facebook.com/video.php?v=435286225735

http://mrskingsbioweb.com/AICE Biology/Plan_diagrams_and_high_power_drawings.pdf
http://hhsibbio09.wikispaces.com/message/view/Topic 9 - Plants/18140315?o=20#18792997
http://click4biology.info/c4b/9/plant9.1.htm
http://sweetibnotes.blogspot.com/2011/07/topic-9-plant-science.html
Vein and artery are quite simple to make though.

Awesooooooooome!! Cha Gaay ho! speechless. . Thanks a lot. very timely help.

 

[Idolfanatic95]

Need help with few mcqs anyone?
May/june 02 paper 1. Q (30)
Oct/nov 02 p1. Q(30) how do we calculate the absorbed oxygen?

 

[Idolfanatic95]

Awesooooooooome!! Cha Gaay ho! speechless. . Thanks a lot. very timely help.

Haha no problem. im actually doing bio these days so you see all this comes so. . .

 

[confused123]

Haha no problem. im actually doing bio these days so you see all this comes so. . .

cool. i have a practical paper on 8th may, and i don't know much about it. actually lack of practice. the last thing i fear is that my grade gets ruined by the practical paper. done with buffering gonna see the video you uploaded.

 

[Student12]

cool. i have a practical paper on 8th may, and i don't know much about it. actually lack of practice. the last thing i fear is that my grade gets ruined by the practical paper. done with buffering gonna see the video you uploaded.

Are you doing varient 33 ??

 

[Idolfanatic95]

http://www.xtremepapers.com/papers/...and AS Level/Biology (9700)/9700_s03_qp_1.pdf
Q(1)
Q (18)
Q(19)
http://www.xtremepapers.com/papers/...and AS Level/Biology (9700)/9700_s05_qp_1.pdf
Q (38)

 

[Idolfanatic95]

cool. i have a practical paper on 8th may, and i don't know much about it. actually lack of practice. the last thing i fear is that my grade gets ruined by the practical paper. done with buffering gonna see the video you uploaded.

Practicals i feel are easy if you get it though. i hate the enzymes ones :/ the timings and readings suck sometimes but anyway Good Luck with your practicals
I'll be taking the other group, 34.
And that video is just the guidelines about plan diagrams. nothing visual. The diagrams wud help or I'll see if i have some of mine drawn, wud post them in here soon.

 

[Idolfanatic95]

cool. i have a practical paper on 8th may, and i don't know much about it. actually lack of practice. the last thing i fear is that my grade gets ruined by the practical paper. done with buffering gonna see the video you uploaded.

 

[confused123]

Are you doing varient 33 ??

Practicals i feel are easy if you get it though. i hate the enzymes ones :/ the timings and readings suck sometimes but anyway Good Luck with your practicals
I'll be taking the other group, 34.
And that video is just the guidelines about plan diagrams. nothing visual. The diagrams wud help or I'll see if i have some of mine drawn, wud post them in here soon.

Oh my mistake, its variant 34th on 22nd of May! i have time! are you guys in lahore? if yes what's your centre for practicals?

@idol; i think the whole idea sucks the dilutions and enzyme ones bother me as well but lets hope for the best. yes plz upload them. that would be gr8! good luck to u as well!