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lysosomes

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lysosomes

Postby vinaya » Sun Oct 08, 2006 1:31 pm

why are lysosomes said to b abundant in secretory cells?
thnx in adv
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Postby MrMistery » Sun Oct 08, 2006 3:38 pm

who said they are? a secretory cell would have a well developed golgi apparatus and endoplasmic reticulum.
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Postby Dr.Stein » Mon Oct 09, 2006 2:04 am

MrMistery wrote:who said they are? a secretory cell would have a well developed golgi apparatus and endoplasmic reticulum.

Lysosome is derived from Golgi's cisternae (budding), and this substances processed in this place come from ER.
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Postby victor » Mon Oct 09, 2006 10:30 am

But I think those're not termed as lysosome, they're termed more proper as vesicles (even though both share the same sacs of enzymes)...
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Postby fluktuacia » Mon Oct 09, 2006 11:50 am

only those vesicles which contain hydrolytic enzymes are called lysosomes
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Postby MrMistery » Mon Oct 09, 2006 6:37 pm

lysosome keef, not lysozyme. lysozyme is the name of an enzyme.
Now, of course there a huge difference between a lysosome and a secretion vesicle. a lysosome if formed by more secretion vesicles that fuse with each other, all containing specific proteins. lysosomal proteins are tagged in the Golgi apparatus using a Mannose-6-phosphate tail. when all these conditions are met, you have got yourself a lysosome. later, endocytotic or phagocytotic vesicles can fuse with the lysosome to direct degradation of various molecules...

Of course if i think of it more closely, a book author who still thinks the world is flat might make a confusion between a lysosome and a vesicle
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Postby MrMistery » Tue Oct 10, 2006 5:16 pm

nice historical context, never knew who discovered lysosomes. They were born in Belgium, which is good to remember..
Now, i have to contradict you. Lysosomes are only found in animal, fungi and heterotrophic protist cells. they are not found in plants and algae. Algae and plant cells contain vacuoles, or phytolysosomes. they are different from lysosomes in shape(much larger, can hold up to 80% of the cell volume) and have some functions that lysosomes don't: in polinnation(they accumulate antocyan pigments), in storage of Ca,Na(plants do not require Na),NO3, Cl- and other inorganic ions. they may have other roles which slip my mind right now. however they do have 2 characteristics common with those of lysosomes: low internal pH(however they have a pH of 2.5-4 as oposed to the pH of 5 of lysosomes) and function in cellular digestion.

Cell bio is cool, isn't it?!
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Postby jnkdna » Tue Oct 10, 2006 6:26 pm

cell bio very difficult for me!!
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Postby MrMistery » Tue Oct 10, 2006 6:36 pm

it is a complex part of biology, but also one of the most interesting..
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Postby jnkdna » Tue Oct 10, 2006 6:39 pm

unfortunately thats the part bio i get mixed up. and thats wer i got my nickname from...
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Postby MrMistery » Wed Oct 11, 2006 5:45 pm

good presentation, but it's missing a few basic things. the m6p tag is attached in the golgi not in the endoplsmic reticulum. and it is sent back after the vesicle arrives at the lysosome, it is not digested.
also i do not know of any lysosomal enzyme that is synthetised in the cytoplasm. all of them are made on the ribosomes on the endoplasmic reticulum.
and you did not say anything about the fact that the enzymes of lysosomes are only active at an acid pH(round 5 is optimal) which is found in the lysosome. Also, i would consider worth saying that most enzymes are located in the lysosomal matrix but a few of them are integrated in the lysosome membrane.
and as i said, they only occur in animal cells.

I think that's about it, your presentation was good to begin with..
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Postby Dr.Stein » Thu Oct 12, 2006 5:39 am

MrMistery wrote:lysosome keef, not lysozyme. lysozyme is the name of an enzyme.

I think keef is correct, he tried to explain this: Lysozyme is lysosome's hydrolytic enzyme

Yes, lysosome is ONE of those vesicles.
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