The Importance of the Carbon Cycle Carbon is the key to Life as we know it—most biological molecules (carbohydrates, lipids, proteins, DNA and RNA) are carbon-based Biological energy – either photosynthetic or chemosynthetic—require carbon compounds Hydrocarbons have served as the most essential fuels during the past 150 years Coal and plant fuels also are carbon-based C is very reactive and rarely uncombined
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