Question regarding double membrane & diffusion

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eleven
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Question regarding double membrane & diffusion

Post by eleven » Tue Mar 27, 2007 2:18 am

Hi,

New to the boards and was wondering if someone could help me with these questions. I study in nightschool and we weren't given textbooks as of yet and even tried searching google, but always didn't get the answers that I needed.

1) What is the difference between a double membrane and a bilayer membrane?

I get the part where the bilayer membrane has the phosphate heads facing the water and the fatty acid tails point towards each other like.

OOOOO - heads
IIIIIIII
IIIIIIII - tails
OOOOO

I just don't know what a double membrane looks like. Is it a set of bilayer membranes?

2) The second question I had was from a review sheet. Why does the cell develop mechanisms for a molecule like glucose to enter by diffusion and active transport? This question is from a review sheet. I'm not really sure what my teacher meant by mechanisms, could someone elaborate on that. I would've asked her, but the day these were handed out we had a substitute teacher.

Sorry if this is a bother and thanks if anyone takes a look at this.

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mith
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Post by mith » Tue Mar 27, 2007 2:58 am

for #2, think of size, then google for glucose transport and facilitated diffusion.
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eleven
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Post by eleven » Tue Mar 27, 2007 3:49 am

Thanks mith. Googled it and found the answer, thanks for the suggestion.

Darby
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Post by Darby » Tue Mar 27, 2007 3:09 pm

You're most of the way there - bilayer is a way of describing a single membrane. Double membrane is just what it sounds like - 2 membranes around something, like a nuclear envelope.

eleven
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Post by eleven » Tue Mar 27, 2007 4:13 pm

Ah, sweet. Thanks Darby. I appreciate the help from both of you.

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