Proteins

Proteins

Proteins are polymers of amino acids that provide structure and control reactions in all cells. When humans think of expressing the meaning of life, they often resort to words. From poems to sonnets to short stories to novels, words tell the stories of life. But in biological terms, the words of life are proteins. While DNA holds the code of life, proteins are the language in which that code is expressed.

To observe the mosaic of proteins in life is to observe nature in its finest array. The feathers of a bird and the silk of a spider's web are both almost pure protein. The most numerous proteins in an animal are the collagen proteins joining animal body parts. Other proteins include the positively charged histone proteins that condense the cell's negatively charged DNA and the transcription factor proteins that control which genes are expressed (made into proteins) and which remain silent. A plant traps CO₂ to make sugar with Earth's most abundant protein, the enzyme ribulose 1,5-biphosphate carboxylase. The protein hemoglobin transports gases through the bloodstream necessary for the metabolism of life. Other proteins store minerals (ferritin) or fats (ovalbumin), contract muscles (myosin), protect against infection (anti-bodies), or act as toxins (botulinum) or hormones (insulin).

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