Molecules: You'd better learn to live with them.
DCMU is a simple aromatic molecule, and a pretty specific electron acceptor for the photosystem II protein found in plants. What does this mean?
Electron transfer reactions are important in all of life; plants use it in photosynthesis. Some DCMU will kill your plants nicely, and it's a broad-spectrum insecticide. Similarly, all eukaryotes use proton transfer in their mitochondrion. This is why 2,4-dinitrophenol will help you lose weight like crazy (if it doesn't kill you, which isn't exactly unlikely). Different mechanism, but you're still collapsing a gradient and wreaking havoc on a vital step in metabolism.
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