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Active Transportation in the human body

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Active Transportation in the human body

Postby thedropsoffire » Sun Aug 05, 2007 9:12 pm

Hey just got a question about phagocytosis, pinocytosis, and receptor-mediated endocytosis. I understand how each work in cells in general, but what are specific examples of each of these types of active transportation in the human body? Thanks
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Postby ididntdoit » Mon Aug 06, 2007 12:47 am

Ok, hopefully this helps a little bit..:)

Phagocytosis- Neurophiles, which make up about 60-70% of all white blood cells use phagocytosis to engulf invading microbes. When a cell is damaged by a microbe, it releases a chemical signal that attracts neutrophils around it. The neutrophils will then draw the invader into them through phagocytosis. The only problem is that neutrophils kinda well, die when they do this, so they have a really short life span. Also monocytes which are about 5% of all white blood cells float around the blood stream, then they form macrophages, which are massive but eating things. They have really big psuedopose which just surround the microbe and draw it in.

I don't know anything about pinocytosis or receptor mediated endocytosis, and i can't find anything :( If I can i'll definately pass it on. Hope the phagocytosis helped though
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Postby thedropsoffire » Mon Aug 06, 2007 7:27 pm

Thank you for that - that certainly explains the phagocytosis in the human body and confirms something that I came across in my research. But if anyone can give examples for the other two - pinocytosis or receptor-mediated endocytosis, it would be greatly appreciated!
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Postby Darby » Mon Aug 06, 2007 11:55 pm

In the example above, the chemicals that set off the process attach to receptors on the macrophages, so you've got the third.

I'm not sure about pinocytosis, but I would suspect that it happens in the distal convoluted tubules of the kidneys, where materials the body needs to discard (but wouldn't go through the filter) are added to urine.
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Postby MrMistery » Sun Aug 19, 2007 8:05 pm

The clasic example of pinocitosis in the human body is how a baby takes up "ready-made" antibodies from his mother in milk, before its own immune system can develop

For receptor-mediated endocytosis. You know that there are two key components: the receptor in the target cell and the and the component that binds to the receptor. I can think of two examples right now.
1. Cholesterol travels in the blood complexed with proteins called apolipoproteins in lipoprotein particles(LDL, HDL etc). When a cell takes up cholesterol from the blood, it takes up the whole particle by receptor mediated endocytosis for apolipoproteins.
2. Iron travels in the blood bound to a protein named transferrin. when a cell needs iron it takes it up from the blood by receptor mediated endocytosis for transferrin.

Regards,
Andrew
"As a biologist, I firmly believe that when you're dead, you're dead. Except for what you live behind in history. That's the only afterlife" - J. Craig Venter
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