[homework help] A question about the cell membrane

[kevin247]

How is the cell membrane of an eukaryotic cell a "selective barrier"? I understand that it allows molecules of certain sizes through, but are there any types of materials it specifically blocks out regardless of their size?

Sorry, this is confusing me. Selective barrier? Like a filter, right?

Clueless. Research is not turning up answers. Help would be appreciated.

[Hippie459MN]

My girlfriend knows about this stuff so this is from her....

The cell membrane is a selective barrier, meaning that it lets some chemicals in and others out and in doing so maintains the balance necessary for the cell to live.

http://animals.about.com/od/animalswildlife101/a/anatomyofacell.htm

Take a look at this web site

[kevin247]

Thanks!