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A level Biology: Post your doubts here!

♣♠ Magnanimous ♣♠

♣♠ Magnanimous ♣♠

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My Name said:
From arteriol end to capillary bed there are sphinter muscles
Please explain
Click to expand...
See sphincter muscles are present at the end of most organs
For example in stomach ---> Pyloric sphincter muscles
Urethra sphincter muscles are present.
Also in the opening of stomach and at the end of esophagus.

Role of sphincter muscles is to block the way of substances for a particular amount of time unless and until a voluntary signal is not passed by CNS.

Same in this case. :)
 
M

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♣♠ Magnanimous ♣♠ said:
See sphincter muscles are present at the end of most organs
For example in stomach ---> Pyloric sphincter muscles
Urethra sphincter muscles are present.
Also in the opening of stomach and at the end of esophagus.

Role of sphincter muscles is to block the way of substances for a particular amount of time unless and until a voluntary signal is not passed by CNS.

Same in this case. :)
Click to expand...
so here they help in maintaining pressure ?and how?
Ty btw :)
 
♣♠ Magnanimous ♣♠

♣♠ Magnanimous ♣♠

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My Name said:
so here they help in maintaining pressure ?and how?
Ty btw :)
Click to expand...
It has role in maintaining pressure.
They help in maintaining pressure of blood that is about to enter capillary. Like -->
In presence of them high blood pressure is created leading to more escape of dissolved substances( more formation of tissue fluid that enters inter cellular spaces) when the blood enter capillary.

Wiki says --> . The sphincter can open and close the entrance to the capillary, by which contraction causes blood flow in a capillary to change as vasomotion occurs.[3] The entire capillary bed may be bypassed by blood flow through arteriovenous anastomoses or through preferential flow through metarterioles.[2] If the sphincter is damaged or can not contract, blood can flow into the capillary bed at high pressures. When capillary pressures are high (as per gravity etc.), fluid passes out of the capillaries into theinterstitial space, and edema or fluid swelling is the result.[citation needed]

Overall they help in maintaining pressure of blood entering in capillary.
 
♣♠ Magnanimous ♣♠

♣♠ Magnanimous ♣♠

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My Name said:
View attachment 50966
Answer is C!
View attachment 50967
Answer is B!

Graph questions annoy me -.-'
Click to expand...
Ques 2)

See first of all blood LEAVING active muscles is deoxygenated which means less conc of oxygen in blood and high conc of CO2 in blood which means the value of percentage saturation of hemoglobin with oxygen will be less.
And here in this graph B has the least value of % saturation of hemoglobin with oxygen so answer is B

I hope you got it..
And I think you should read some particular topics for understanding the graphs. I know they confuse us but the best solution is to read again and again and if you get any doubt related to them PM me :)
Read topics on page 154 - 158 thoroughly :) (Third edition of Biology coursebook)
 
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♣♠ Magnanimous ♣♠ said:
Ques 2)

See first of all blood LEAVING active muscles is deoxygenated which means less conc of oxygen in blood and high conc of CO2 in blood which means the value of percentage saturation of hemoglobin with oxygen will be less.
And here in this graph B has the least value of % saturation of hemoglobin with oxygen so answer is B

I hope you got it..
And I think you should read some particular topics for understanding the graphs. I know they confuse us but the best solution is to read again and again and if you get any doubt related to them PM me :)
Read topics on page 154 - 158 thoroughly :) (Third edition of Biology coursebook)
Click to expand...
I will go study this topic again.
Thank you very much for your help :)
 
Liv2Stdy

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My Name said:
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_w10_qp_21.pdf
question 5 part d

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s11_qp_23.pdf
question 2 part c

Plz and thnx
Click to expand...

Answer for M/J '11 (23) Q2 part c,

3 DNA nucleotides (Nitrogenous bases actually!)code for 1 amino acid.
There are 238 amino acids in this polypeptide.

So the number of DNA nucleotides required to code for a polypeptide with 238 amino acids = 238 x 3 = 714

Answer for O/N '10 (21) Q5 part d,

There isn't much to this, you just have to explain the process of protein synthesis starting from ribosome -> Endoplasmic reticulum -> Golgi apparatus -> Exocytotic vesicle -> cell membrane (This is the information you can get from the figure!). Also explain all the processes happening at each cell organelle.

There is a small diagram in Mary Jones Revision guide for this. Refer to it too!
 
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Liv2Stdy said:
Answer for M/J '11 (23) Q2 part c,

3 DNA nucleotides (Nitrogenous bases actually!)code for 1 amino acid.
There are 238 amino acids in this polypeptide.

So the number of DNA nucleotides required to code for a polypeptide with 238 amino acids = 238 x 3 = 714

Answer for O/N '10 (21) Q5 part d,

There isn't much to this, you just have to explain the process of protein synthesis starting from ribosome -> Endoplasmic reticulum -> Golgi apparatus -> Exocytotic vesicle -> cell membrane (This is the information you can get from the figure!). Also explain all the processes happening at each cell organelle.

There is a small diagram in Mary Jones Revision guide for this. Refer to it too!
Click to expand...
Okay Thank you
upload_2015-3-18_15-21-35.png
This figure right?
So I write that....
The protein are made in the RER and pinched out into vesicles then modified in the Golgi Apparatus.
The modified proteins from the Golgi Apparatus break away and fuse with the cell surface membrane and release the modified proteins.
 
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Abdul Aziz Jamil said:
M/J 13 paper 21
Q6 b describe the experimental evidence that show that smoking causes lung cancer
Click to expand...
There was an experiment with dogs.
Half of them were made to smoke filter tipped cigarette ( these have low tar) and the other half were made to smoke plain cigarettes. The ones who smoked the infilterrred one developed cancer but the ones who smoked the filtered one did not develop cancer.

There was another experiment with rats their skin was painted with tar and they to developed cancer.

Hope that helps
 
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explain the link between infection of T- lymphocytes by HIV and the onset of the symptoms of AIDS
 
Liv2Stdy

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My Name said:
Okay Thank you
View attachment 51201
This figure right?
So I write that....
The protein are made in the RER and pinched out into vesicles then modified in the Golgi Apparatus.
The modified proteins from the Golgi Apparatus break away and fuse with the cell surface membrane and release the modified proteins.
Click to expand...
Hmm Yes, that's correct. I would add a bit more at the "modified in the Golgi Apparatus" - like how it is modified within brackets....
Golgi1.jpg
I'm not saying you need to write everything.....i don't think that its needed but its always good to show that you know something beyond the basic explanation. Also mention exocytosis at the end but your answer is correct and will probably not any lose marks :) .
 
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