If you’re familiar with chemistry, or farming, you may have heard the words “organic” and “inorganic” bandied about – molecules can be organic, and so can beef or broccoli – but what do these words actually mean, and can they be applied to humans? Are our bodies organic or inorganic?

Organic vs Inorganic

“There isn’t a super strict definition for these terms that everyone agrees on,” Eric Galbraith, a professor in the Department of Earth and Planetary Sciences at McGill University, told IFLScience.

“In general, organic compounds include most of the molecules that contain carbon atoms that are attached to hydrogen and/or other carbon atoms.”

As well as carbon and hydrogen, organic compounds may contain other elements, such as oxygen, nitrogen, sulfur, or phosphorus. They are also derived from or produced by living organisms. 

This is very different from the definition of organic that relates to foodstuffs, which generally means their production does not involve the use of chemical fertilizers, pesticides, or other artificial chemicals.

Some examples of organic compounds include methane (CH₄), glucose (C₆H₁₂O₆), and DNA. “They also include petroleum and plastics,” Galbraith added. “So organic, to a chemist, doesn’t mean natural – or healthy!”

Inorganic compounds, meanwhile, are not derived from living things and do not contain carbon-hydrogen bonds. Therefore, sodium chloride (NaCl), ammonia (NH₃), and calcium chloride (CaCl) are all inorganic compounds.

What is the human body made of?

As complex as the human body is, it can be boiled down to a handful of elements. Around 99 percent is made up of just six elements: oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorus. Around 65 percent of our mass comes from oxygen, 18.5 percent from carbon, and 9.5 percent from hydrogen.

Another five elements – sulfur, potassium, sodium, chlorine, and magnesium – make up 0.85 percent of the remaining mass, while the rest is comprised of trace elements.

In total, there are over 60 elements found in the human body – most of which (bar hydrogen, whose origins can be traced back to the beginning of the universe) come from ancient stars.

The vast majority occur in minute quantities, Elisabeth Ratcliffe, of the Royal Society of Chemistry, told The Independent. “Some people are surprised at how little of some elements is needed to support life. For example iron, which is so important for transporting oxygen around the body, only makes up 0.006 percent of our chemical composition.”

In the human body, these elements are often found as compounds, which can be organic or inorganic.

Organic compounds are found in every cell of the body and are essential for normal cellular metabolism and function. They “include all the important molecules of life, such as proteins, sugars, fats, and DNA,” Galbraith said.

But there are some equally important inorganic molecules inside of us: “Water, dissolved oxygen and carbon dioxide in our blood, some mineral crystals in our bones and ears,” Galbraith explained.

“Lots of the human body is water, an inorganic compound” – up to 60 percent, in fact, and more in some organs.

“But all of the interesting part is organic.”

Are humans organic or inorganic?

Humans are living creatures and, clearly, we’re made up of lots of important, carbon-containing compounds, so it would be easy to write us off as organic and leave it at that. But, as we’ve established, inorganic compounds are also essential for sustaining life. So which is it?

“All the distinctive living parts [of humans] are organic,” Galbraith told IFLScience. “In fact, we often refer to living things in Earth science as ‘organic matter’.”

“But there would be no life without the exchange between organic and inorganic compounds, most importantly O₂ and CO₂.”

As ever with questions like this, the answer is not straightforward. The human body is just a bit more complicated than that.

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