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Name: Catalina
Status: Other
Grade:  Other
Location: WI
Country: United States
Date: October 2007

In dead organisms, what macromolecule decomposes first, DNA or proteins?

Both proteins and nucleic acids start to decompose right away. There are chemicals in organisms called enzymes that begin to break things down right away. Enzymes are at work in living organisms as well, cleaning up bits of stuff that would otherwise build up. Once an organism dies, it stops making new proteins and other building blocks of life. But, the enzymes are still there, and they keep working. Very soon after an organism dies, other scavengers come along (like bacteria or fungi) and further break down the dead organism.

Proteins are mostly just useful as food once an organism dies (another organism can't come in and re-used them, other than as food). Even though proteins begin degrading right away, that doesn't mean they're not useful anymore. They still can be used as food even though they've broken down. You can store meat for years and have it still be nutritious (dried or salted meats, for instance).

DNA isn't that useful as energy (there's not enough of it), and can't be used easily by another organism either (there are special lab techniques that allow genes to be transferred, but it's not something anyone/anything can do). Except for some special scientific techniques, once an organism dies, its DNA goes with it.

Hope this helps,

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