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A level Biology: Post your doubts here!

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Bba321

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Tasneeem said:
The process of phagocytosis:
1. In the tissues attacked by pathogens mast cells produce histamine which causes inflammation and attract neutrophils.
2. Iflammation means that blood vessels dilate so more blood reaches site of attack and making capillaries leaky so phagocytes can ne squeezed out.
3. Neutrophils attracted towards the antigens by chemotaxis
4. Bacteria may be attracted directly to the membrane of neutrophil or marked by an antibody or plasma protein as the surface of neutrophil contains receptors for antibodies and plasma protein where they can be fiitted to stimulate the process of phagocytosis. (plasma protein used in marking antigen in known as complement or opsonin protein)
5. Pathogen is engulfed and taken in a vesicle by endocytosis.
6. Lysosomes fuse with the phagocytotic vesicle where bacteria are killed by free radicals, H2O2 and digested by enzymes.
Tasneeem said:
The process of phagocytosis:

Thankssss Tasneem :D
Can you also tell me if we have to write about macrophages and all in this?
Click to expand...
Click to expand...
 
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Tasneeem

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No because macrophages have their role as an antigen presenting cell (APC)
Macrophage engulfs pathogen and then expose its antigens on its surface to stimulate immune system to be prepared to attack this type of antigen. This process known as antigen presentation.
 
shaminou

shaminou

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Tasneeem said:
The process of phagocytosis:
1. In the tissues attacked by pathogens mast cells produce histamine which causes inflammation and attract neutrophils.
2. Iflammation means that blood vessels dilate so more blood reaches site of attack and making capillaries leaky so phagocytes can ne squeezed out.
3. Neutrophils attracted towards the antigens by chemotaxis
4. Bacteria may be attracted directly to the membrane of neutrophil or marked by an antibody or plasma protein as the surface of neutrophil contains receptors for antibodies and plasma protein where they can be fiitted to stimulate the process of phagocytosis. (plasma protein used in marking antigen in known as complement or opsonin protein)
5. Pathogen is engulfed and taken in a vesicle by endocytosis.
6. Lysosomes fuse with the phagocytotic vesicle where bacteria are killed by free radicals, H2O2 and digested by enzymes.
Click to expand...
Is it also found in AS biology??
 
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Tasneeem

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shaminou said:
Thanks a whole lot.:)
Can you tell me how to measure cell diameter with an eyepiece graticule please?? :)
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you have to caliberate first the eye piece graticule to determine the size of the graticule unit in mm or um
then remove the stage micrometer and put the slide to determine its size in graticule units
then cross multiplication
Ex. if 100 eye piece graticule divisions measures 0.25mm, therefore each graticule unit equal to 0.25mm divided by 100=2.5um
 
shaminou

shaminou

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Tasneeem said:
you have to caliberate first the eye piece graticule to determine the size of the graticule unit in mm or um
then remove the stage micrometer and put the slide to determine its size in graticule units
then cross multiplication
Ex. if 100 eye piece graticule divisions measures 0.25mm, therefore each graticule unit equal to 0.25mm divided by 100=2.5um
Click to expand...
With what apparatus shall you determine the size of eyepiece graticule??
 
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