system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: If Blood Plasma is 95% water, why is it so precious?

I donate blood plasma bi-monthly. and one of the things that has  bugged me is the high water content. around 19/20's of it is just plain water.

It seems like it that would leave a relatively minor part of it to synthesize.. so why is blood plasma so precious that encouraging people to sign up for having needles stuck in them is the most efficient way of obtaining it?
gpt
The minority component of plasma that is so precious is the variety of proteins in it.  Proteins are very long, complex molecules that your body makes to take care of all sorts of things, including carrying different types of nutrients, mediating cell reproduction, and making other molecules your body needs.  Proteins are extremely difficult to synthesize in a lab, so it's more than worth it to ask people to donate blood plasma.