There are 118 items on the periodIc table, and you might think that we are made up of many of them. But that is not the case; The complex systems that make up our body have a surprisingly simple elementary structure.
“Out of 118 elements, the last thing I read was that 97% of our body weight is made up of just four elements,” Steven Townsend, an organic chemist at Vanderbilt University, told Live Science. These four elements are oxygen, carbon, hydrogen and nitrogen. So what exactly do these elements do?
Oxygen definitely takes the number one spot, accounting for 65% to 67% of the human body’s weight, Townsend said. That’s because our bodies are mostly water – about 50% to 60% – so most of the oxygen is the “O” in H2O. Oxygen is also crucial for energy production and metabolismor the chemical processes that go on in the body, according to a 2016 review in the journal Nature Reports Cancer.
Next comes carbon, which makes up about 18 to 19 percent of body weight, Townsend said, which isn’t surprising given carbon is a major component of most life Earth. Carbon forms the backbone of fats, carbohydrates and proteins, so this element is an important building block of the body and the foods we use to fuel it.
Hydrogen comes in third place. There is more hydrogen atoms in the human body than any other element, but it accounts for only 9 to 10% of the mass of our body. Hydrogen is the other element in H2O, and for every oxygen atom there are two hydrogen atoms. In addition, hydrogen is an important component of proteins, carbohydrates and fats. But although hydrogen contains the majority of atoms, its mass is significantly higher: oxygen and carbon have atomic weights almost 16 and 12 times that of hydrogen, respectively. In other words, it takes 16 hydrogen atoms to reach the mass of one oxygen atom, so hydrogen is only a tenth of our mass.
Number four is the most abundant gas in Earth’s atmosphere at around 3%: nitrogen, according to Townsend. Nitrogen is crucial for proteins and their building blocks, called amino acids. Nitrogen is also a major component of DNS and RNA, including their nitrogenous bases. Both have cytosine, adenine and guanine; DNA has thymine and RNA sports uracil. In other words, without nitrogen, the cells in your body would not be able to store genetic information or replicate. A bonus element, the fifth most abundant in the human body, is calcium, which makes up 1% to 2% of human mass. More than 99% of this calcium is found in the bones and teeth National Health Institute.
But elements other than these top five are important, Townsend said. Take sodium for example. It only makes up 0.2% of the body, but “it’s a super important mineral — it helps balance the fluids in the body,” he said. When sodium is out of balance, people can have significant health problems, such as high blood pressure or loss of kidney function.
“[The human body is] complicated, but I think it’s also amazing in its simplicity,” Townsend said. “The complex interconnected systems that keep us alive – they all depend on a handful of elements. When you consider how complex the human body is, it’s kind of magical.”
Originally published on Live Science.
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