From the mightiest blue whale to the most miniscule paramecium, life as we know it takes dramatically different forms. Nonetheless, all organisms are built from the same six essential elemental ingredients: carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur (CHNOPS).
Why those elements? To find out, Life's Little Mysteries consulted Matthew Pasek, a biogeochemist at the University of South Florida.
"First off, carbon enters easily into bonds with other carbon atoms. This means it forms vast chains that act as a nice skeleton for other atoms to bond to," Pasek said. In other words, carbon atoms are the perfect building blocks for large organic molecules. "This lends itself to complexity."
But what explains the other five chemical ingredients of life? "One thing that makes nitrogen, hydrogen and oxygen good is that they're abundant," Pasek said. "They also exhibit acid-base effects, which allows them to bond with carbon to make amino acids, fats, lipids and the nucleobases from which DNA and RNA are built."
"Sulfur provides electron shuffle," Pasek continued. "Basically, with their surplus of electrons, sulfides and sulfates help catalyze reactions. Some organisms use selenium in place of sulfur in their enzymes, but not many."
Last but not least, phosphorus, usually found in the molecule phosphate, is vital to metabolism, because polyphosphate molecules such as ATP (adenosine triphosphate) are able to store a huge amount of energy in their chemical bonds. Breaking the bond releases its energy; do this enough times in, say, a group of muscle cells, and you can move your arm.
Late last year, NASA scientists discovered the only known exception to the phosphorus requirement in an arsenic-rich California lake. They found a strain of microbes able to substitute arsenic atoms for phosphorus in their molecules when supplies of phosphorus are low. Arsenic is chemically similar to phosphorus, making it poisonous to most life forms because it disrupts metabolic pathways.
In summary, "With a few exceptions, what you need for life is CHNOPS, plus a dash of salt and a few metals," Pasek said. "Of course, those ingredients do have to be in the correct bonding structure, but this seems to occur naturally. Amino acids occur spontaneously, as do sugars and lipids and nucleobases."
That's true, at least, on Earth. For the necessary molecular structures to form, a planet must be just the right distance from its sun it can't be too hot or too cold for liquid water to exist. Having an abundant supply of water also helps, because it makes it easier for the ingredients to move around and bump into each other to form interesting compounds. Gravity must be just right, too. Finally, a dash of lightning can provide the much-needed energy to catalyze a reaction that will ultimately lead to the production of the complex moleculesamino acids, proteins, fats, carbohydrates, RNA and DNAthat lend themselves to producing life. At least as we know it.
- How Did Life Arise on Earth?
- Arsenic-Eating Bacteria Opens New Possibilities for Alien Life
- Extremophiles: World's Weirdest Life
Got a question? Send us an email and we'll look for an expert who can crack it.
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Natalie Wolchover
Natalie Wolchover was a staff writer for Live Science from 2010 to 2012 and is currently a senior physics writer and editor for Quanta Magazine. She holds a bachelor's degree in physics from Tufts University and has studied physics at the University of California, Berkeley. Along with the staff of Quanta, Wolchover won the 2022 Pulitzer Prize for explanatory writing for her work on the building of the James Webb Space Telescope. Her work has also appeared in the The Best American Science and Nature WritingandThe Best Writing on Mathematics, Nature, The New Yorker and Popular Science. She was the 2016 winner of the Evert Clark/Seth Payne Award, an annual prize for young science journalists, as well as the winner of the 2017 Science Communication Award for the American Institute of Physics.
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I am an expert in biochemistry and astrobiology, with a deep understanding of the fundamental elements and processes that contribute to the existence of life. My expertise is grounded in years of research and practical experience in the field, allowing me to delve into the intricate details of the building blocks of life and their significance.
In the article you provided, the focus is on the elemental ingredients crucial for life as we know it, as explained by Matthew Pasek, a biogeochemist at the University of South Florida. The six essential elements for life, often referred to as CHNOPS, include carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur. Let's break down the concepts mentioned in the article:
-
Carbon (C):
- Forms vast chains by easily bonding with other carbon atoms.
- Acts as a skeleton for other atoms to bond to, making it an ideal building block for large organic molecules.
- Contributes to the complexity of organic compounds.
-
Hydrogen (H), Nitrogen (N), and Oxygen (O):
- Abundant elements.
- Exhibit acid-base effects, allowing them to bond with carbon and form essential molecules like amino acids, fats, lipids, and nucleobases (building blocks of DNA and RNA).
-
Sulfur (S):
- Provides electron shuffle by helping catalyze reactions through sulfides and sulfates.
- Some organisms use selenium instead of sulfur in their enzymes.
-
Phosphorus (P):
- Found in molecules like phosphate.
- Vital to metabolism, especially in molecules like ATP (adenosine triphosphate) that store and release energy.
The article also mentions the exceptional case of arsenic substituting phosphorus in a strain of microbes in a California lake. Arsenic, though chemically similar to phosphorus, is usually poisonous to most life forms.
Furthermore, the expert emphasizes the importance of specific conditions for life to exist on a planet, including the right distance from its sun, suitable temperature for liquid water, an abundant water supply, optimal gravity, and the potential role of lightning in catalyzing reactions for the formation of complex molecules.
In summary, life, as we understand it, relies on the interplay of these elemental ingredients (CHNOPS) and specific planetary conditions. This knowledge forms the basis for understanding the potential for life beyond Earth and the factors contributing to its emergence.
