A level Biology: Post your doubts here!

[knowitall10]

You forgot to draw the plasmodesmata.

oh
thx..i told u i was never gud

 

[IsaacNewton]

Shalt any one of you guilluible earthlings require words of wisdom regarding a matter of study of life and its forms, shall you inform me privately so I may address your concerns.

AKA. Feel free to PM if you have any questions.

 

[Alice123]

Can u write the ans orderly??? your help will be highly appreciated....Irfan1995
Describe how non-cyclic photophosphorylation produces ATP and reduced NADP
(a) 1. photosystem I (PI) and photosystem II (PII) involved ;
2. light harvesting clusters ;
3. light absorbed by accessory pigments ;
4. primary pigment is chlorophyll a ;
5. energy passed to, primary pigment / chlorophyll a ;
6. electrons, excited / raised to higher energy level ;
7. (electrons) taken up by electron acceptor ;
8. (electrons) pass down electron carrier chain (to produce ATP) ;
9. PII has (water splitting) enzyme ;
10. water split into protons, electrons and oxygen ; A equation
11. photolysis ;
12. electrons from PII pass to PI / electrons from water pass to PII ;
13. to replace those lost ; give either in relation to PI or PII
14. protons and electrons combine with NADP (to produce reduced NADP) ;
can award these marking points from a diagram

 

[Irfan1995]

Can u write the ans orderly??? your help will be highly appreciated....Irfan1995
Describe how non-cyclic photophosphorylation produces ATP and reduced NADP
(a) 1. photosystem I (PI) and photosystem II (PII) involved ;
2. light harvesting clusters ;
3. light absorbed by accessory pigments ;
4. primary pigment is chlorophyll a ;
5. energy passed to, primary pigment / chlorophyll a ;
6. electrons, excited / raised to higher energy level ;
7. (electrons) taken up by electron acceptor ;
8. (electrons) pass down electron carrier chain (to produce ATP) ;
9. PII has (water splitting) enzyme ;
10. water split into protons, electrons and oxygen ; A equation
11. photolysis ;
12. electrons from PII pass to PI / electrons from water pass to PII ;
13. to replace those lost ; give either in relation to PI or PII
14. protons and electrons combine with NADP (to produce reduced NADP) ;
can award these marking points from a diagram

Non-cyclic photophosphorylation involves both light-harvesting clusters called photosystems (PS I and PS II). Light is first absorbed by the accessory pigments which transfer the energy to the reaction centre/primary pigment which is made from chlorophyll a. This excites electrons from PS II and releases them to a higher energy state where they are taken up by electron acceptors which pass it down the ETC in order to absorb the energy to be converted to ATP. After most of the energy has been absorbed, the electron is deposited to PS I where the system starts all over again. As you can see, PS II will continuously lose electrons; those electrons must be replaced by the photolysis of water through enzymes found in PS II: 2H2O --> 4H+ + 4e- + O2. Oxygen is lost as a waste product while the electrons combine with the hydrogen ions with NADP to produce NADPH (or reduced NADP).

I think that's all 14 points. You don't have to mentioned them exactly in the order of the mark scheme; all you have to do is arrange them in an 'understandable'way

 

[Alice123]

Non-cyclic photophosphorylation involves both light-harvesting clusters called photosystems (PS I and PS II). Light is first absorbed by the accessory pigments which transfer the energy to the reaction centre/primary pigment which is made from chlorophyll a. This excites electrons from PS II and releases them to a higher energy state whhhere they are taken up by electron acceptors which pass it down the ETC in order to absorb the energy to be converted to ATP. After most of the energy has been absorbed, the electron is deposited to PS I where the system starts all over again. As you can see, PS II will continuously lose electrons; those electrons must be replaced by the photolysis of water through enzymes found in PS II: 2H2O --> 4H+ + 4e- + O2. Oxygen is lost as a waste product while the electrons combine with the hydrogen ions with NADP to produce NADPH (or reduced NADP).

I think that's all 14 points. You don't have to mentioned them exactly in the order of the mark scheme; all you have to do is arrange them in an 'understandable'way

Thankyou sooo muchh.... May Allah bless u n yr family!!!

 

[Vikings]

Re: Stuck in Biology?? Post your doubts here!!


Molecules having partially positive and partially negative charge.

The partial positive or negative charge is due to the electronegativity between the atoms bonded together.

 

[Wanderer]

Revise the sigmoid curve from igcse and the structure of the antibody from AS, i've seen a recent question on it....and do all the questions on biotechnology..the mark scheme has different methods that aren't mentioned in the book
In the end: Pray The best of all things to maintain

Thanks a lot
Indeed...prayers are important

 

[Vikings]

Re: Stuck in Biology?? Post your doubts here!!


Any other definition?!

The time taken for the axon to restore its resting potential, after an action potential is known as the Refractory Period. During this time
the distribution of the sodium & potassium ions return back to normal. No action potential will be generated within the refractory period.

 

[raamish]

can anybody explain what is meant by divergence and how to answer qs5b of J10/42
qp: http://papers.xtremepapers.com/CIE/...nd AS Level/Biology (9700)/9700_s10_qp_42.pdf

 

[Irfan1995]

can anybody explain what is meant by divergence and how to answer qs5b of J10/42
qp: http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s10_qp_42.pdf

Divergence pretty much means the deviation from the original (i.e. how different the DNA is from the original sample).

If a mutation is harmful, then it would shorten the lifespan of the organism, so he will not give the trait to his offspring.
But if a mutation is harmless, then it wouldn't affect the organism, so he could pass on the gene to his offspring.
So there are some areas which are more prone to mutation than others. That is, there is a high chance of mutation which produces harmless effects and will be passed on to the next generation.

 

[raamish]

Divergence pretty much means the deviation from the original (i.e. how different the DNA is from the original sample).

If a mutation is harmful, then it would shorten the lifespan of the organism, so he will not give the trait to his offspring.
But if a mutation is harmless, then it wouldn't affect the organism, so he could pass on the gene to his offspring.
So there are some areas which are more prone to mutation than others. That is, there is a high chance of mutation which produces harmless effects and will be passed on to the next generation.

from which book did u read this. I study bio a2 from mary jones and it did not have this information i think. So is there any additional material which is in the syllabus but not present in the mary jones book?

 

[Alice123]

please help with this...havent evr heard of ornithine cycle before
Describe how nitrogenous waste products are formed and explain why they need to be removed from the body.
deamination;
ref. to ornithine cycle ;
ref. to not all urea / produced each day / always some present ;
ref. to urea ;
ref. to creatinine and uric acid ;
and ammonium ions ;
produced in liver ;
continuously / from excess amino acids ;
toxic ;
if allowed to accumulate ;
ref. to potential damage to tissues ;
ref. to not all urea / that produced each day

 

[Noor Ahmad]

please help with this...havent evr heard of ornithine cycle before
Describe how nitrogenous waste products are formed and explain why they need to be removed from the body.
deamination;
ref. to ornithine cycle ;
ref. to not all urea / produced each day / always some present ;
ref. to urea ;
ref. to creatinine and uric acid ;
and ammonium ions ;
produced in liver ;
continuously / from excess amino acids ;
toxic ;
if allowed to accumulate ;
ref. to potential damage to tissues ;
ref. to not all urea / that produced each day

Do not panick,it isn't difficult.
Well,the ornithine cycle is nothing but the urea cycle.
Excess amino acids breakdown forming ammonia and ketoacids.
Amonnia enters the ornithine cycle where it combibines with carbon dioxide.
Here's the cycle.
Tried making as simple as possible.
Im sure you'll understand it.

 

[Zari]

Asalamualikum
M/J 07 Q3 a) iii) http://papers.xtremepapers.com/CIE/...and AS Level/Biology (9700)/9700_s07_qp_4.pdf
http://papers.xtremepapers.com/CIE/...and AS Level/Biology (9700)/9700_s07_ms_4.pdf
can anyone explain what is vertical and horizontal transmission linked with bacteria ?

 

[Irfan1995]

from which book did u read this. I study bio a2 from mary jones and it did not have this information i think. So is there any additional material which is in the syllabus but not present in the mary jones book?

I don't take A2 Biology, I'm only sitting for the exams.
Our school offers AP Biology, which is far more advanced then the A2 standard.

 

[Irfan1995]

Asalamualikum
M/J 07 Q3 a) iii) http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s07_qp_4.pdf
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s07_ms_4.pdf
can anyone explain what is vertical and horizontal transmission linked with bacteria ?

In short, vertical transmission is the transmission of genetic material from parents to offspring. So if a bacterium has, for example, an antibiotic-resistance gene, it can transfer this allele to its offspring by vertical transmission (or asexual reproduction)

Horizontal transmission is when two bacteria share genetic material between themselves. Plasmids are very small, so they can diffuse easily between two bacteria. So if one bacterium has an antibiotic-resistance gene, it can transfer this allele to another bacterium by simple direct contact.

 

[Zari]

In short, vertical transmission is the transmission of genetic material from parents to offspring. So if a bacterium has, for example, an antibiotic-resistance gene, it can transfer this allele to its offspring by vertical transmission (or asexual reproduction)

Horizontal transmission is when two bacteria share genetic material between themselves. Plasmids are very small, so they can diffuse easily between two bacteria. So if one bacterium has an antibiotic-resistance gene, it can transfer this allele to another bacterium by simple direct contact.

JazakAllah for the reply May Allah Bless you always

 

[strangerss]

What is the formula for maximum percentage error in any apparatus?

 

[strangerss]

Can some one please check if this plan diagram is correct?The real image is in this link :http://www.wesapiens.org/class/2843...on+between+bronchiole+and+terminal+bronchiole and this is my image :

 

[knowitall10]

Can some one please check if this plan diagram is correct?The real image is in this link :http://www.wesapiens.org/class/2843005/file/9/Lung, Transition between bronchiole and terminal bronchiole and this is my image :

Yeah... nothing really seems to be wrong with it...