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A level Biology: Post your doubts here!

Karim Nabil

Karim Nabil

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Snowysangel said:
Ohh. Wait but then when do the antibodies attach to the mast cell? In secondary responses its when the pathogen attaches to the antibodies on the mast cell that the mast cell releases histamine right? Could you elucidate the events that take place in the primary allergic response please
Also how are the bronchi involved in gaseous exchange and the trachea isn't?
Click to expand...
They bind to the mast cells for triggering them to release histamine and cause inflammation. Then an immune response is stimulated, attracting nearby neutrophils to the antigen.the neutrophil recognize and then attach to the antigen, engulf it by phagocytosis, then it is digested and released out of neutrophil by exocytosis, it can also act as antigen presenting cell, then if the antigen is in body-cells, cell mediated response stimulated(t-cells), but if outside cells in tissue fluid then humoral response stimulated(b-cells)
T-cells with complementary receptors to the antigen is activated then and divide by mitosis, then action is taken depending on its type.
In b-cells, those with specific antibody receptors are only selected(clonal selection), then they divide differentiating into plasma cells (that secrete antibodies) and memory cells.
Only alveolus, alveolar duct is involved in gaseous exchange.
 
Mayisha M

Mayisha M

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XPFMember said:
Hi everyone, assalamoalaikum!! :)

To get things organized in a better way, I am making this thread. As othewise, some queries remain unanswered!

So post your A LEVEL BIOLOGY doubts in this thread. InshaAllah those who can , will help me and you all. :D ;)

Will try to update this soon, by adding links to some Biology Notes & Links around the forum.

Thanks!
Jazak Allah Khair!

BIOLOGY LINKS & NOTES :


B!0l0gy $l!de$ & N0te$... :) - by workinghard

Biology Practical notes!! - by libra94

http://www.biologymad.com

http://www.biologyinnovation.co.uk

Action Potential - Notes
Click to expand...


Hi guys.
please help me understand this
one. I found this really complicated.

http://papers.xtremepapers.com/
CIE/...nd AS Level/Biology
(9700)/9700_s13_qp_13.pdf

Number 15.
The answer is .
Explanation needed
 
Last edited:
K

kitkat <3 :P

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Mayisha M said:
Hi guys.
please help me understand this
one. I found this really complicated.

http://papers.xtremepapers.com/
CIE/...nd AS Level/Biology
(9700)/9700_s13_qp_13.pdf

Number 14.
The answer is C.
Explanation needed
Click to expand...
competitive inhibitors are the type of inhibitors who keep on attaching and detaching from the substrate that why increasing the substrate means more substrate is able to attach so rate of reaction increase hope it helped :)
 
MÁťT PŭמҚ

MÁťT PŭמҚ

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thats_me said:
The no. Of samples will be given in the question's first part or some where earlier in the question
it'll be( n1+n2 -2) where n is the no. Of samples

Did you get the standard error & t value? In ii & iii part?
If yes then Which part do you have problem with confidence interval or the mean?

By adding all the values of observed & dividing them by 3
So 36+90+114=240/3=80
Click to expand...

thnkx! but for the first question thy dint mention any number of samples!!
and i have problem in confidence interval!
 
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