Natural and Synthetic Macromolecules
Simple Explanation
Natural macromolecules — proteins, carbohydrates (like starch and cellulose), nucleic acids (DNA, RNA) — are produced by living organisms. Synthetic macromolecules — like polyethylene, nylon, and PVC — are manufactured by chemists, typically from small molecules derived from petroleum.
Why Do We Need It?
Comparing natural and synthetic macromolecules highlights both what chemistry has learned from nature (many synthetic polymers are inspired by natural ones) and where the two diverge — notably in biodegradability, since most natural macromolecules break down readily in the environment while many synthetic ones persist for a very long time.
Why Does This Work?
Natural macromolecules are built by living cells using enzymes finely tuned to construct AND break down specific molecular structures, meaning other organisms in the environment usually have matching enzymes able to decompose them. Many synthetic polymers, by contrast, have molecular structures that no natural enzyme evolved to break down, so they persist in the environment for decades or centuries rather than being decomposed on a reasonable timescale.
Real-Life Example
Cellulose vs. plastic in the environment
A wooden object (mostly cellulose) decomposes in the environment within years, while a plastic object can persist for centuries.
Cellulose is a natural macromolecule that many fungi and bacteria have evolved enzymes to break down, so wood decomposes relatively quickly; most synthetic plastics have no natural enzyme equipped to break their specific molecular structure apart, so they persist far longer in the environment.
Practice
Why do most synthetic plastics persist in the environment far longer than natural macromolecules like cellulose?
MediumCommon mistake
Assuming ALL synthetic macromolecules are equally non-biodegradable, or that ALL natural macromolecules decompose quickly — biodegradability actually depends on the SPECIFIC molecular structure involved, and some newer synthetic polymers are deliberately engineered to be biodegradable.
Quick Review
- Natural macromolecules (proteins, DNA, starch) are produced by living organisms.
- Synthetic macromolecules (polyethylene, nylon, PVC) are manufactured, often from petroleum.
- Biodegradability depends on whether matching decomposing enzymes exist in the environment.