Question

What gives carbon its unique characteristics? How is this connected to life?  Please answer in greater than 150 words.

Answer 1

Carbon is one of the few elements to be able to bond with itself to form huge (macromolecules) molecules. Carbon almost always has an octet of electrons around it and can form double and triple bonds when pi bonds are formed (side to side overlap of unhybridized p-orbitals). Carbon can have sp, sp2 and sp3 hybridization. Carbon can exhibit a range of oxidation numbers from +4 to -4.

Carbon is essential to the circle of life. Regardless of its source, this energy is used to synthesise complex organic molecules from simpler inorganic compounds such as carbon dioxide (CO2) and water (H2O). The following two equations are simplified representations of photosynthesis (top) and (one form of) chemosynthesis (bottom) :

CO2 + H2O + light \rightarrow CH2O + O2
CO2 + O2 + 4 H2S \rightarrow CH2O + 4 S + 3 H2O

In both cases, the end point is reduced carbohydrate (CH2O), typically molecules such as glucose or other sugars. These relatively simple molecules may be then used to synthesise further more complicated molecules, including proteins, complex carbohydrates, lipids, and nucleic acids, or be respired to perform work. Consumption of primary producers by heterotrophic organisms, such as animals, then transfers these organic molecules (and the energy stored within them) up the food chain, fueling all of the Earth's living systems.