Rucete ✏ Campbell Biology In a Nutshell
Carbon is the backbone of life as we know it. From tiny methane molecules to complex proteins, the diversity of carbon-based compounds makes life possible. This section explores how organic chemistry helps explain the origin of life, with a little help from a spark and a few gases in a flask.
Unit 1 THE CHEMISTRY OF LIFE
Concept 4.1 Organic Chemistry is the Study of Carbon Compounds
1. Organic Chemistry and the Origin of Life
Organic chemistry studies compounds containing carbon. These compounds range from the very simple (like CH₄) to the very complex (like proteins). Because carbon can form four covalent bonds, it acts like a molecular "connector," enabling the formation of large, diverse molecules.
Stanley Miller's famous 1953 experiment simulated early Earth conditions. He used water vapor, gases (H₂, CH₄, NH₃), and electrical sparks to mimic lightning. The result? A variety of organic molecules formed spontaneously, including amino acids—some of life’s essential building blocks.
This experiment was a milestone, showing that complex organic molecules might have originated abiotically—without life—on the early Earth. Later experiments with updated gas mixtures still supported this idea, strengthening the hypothesis that life could have emerged from non-living matter.
2. Carbon-Based Compounds Found on Mars?
NASA's Curiosity rover found carbon-based compounds in a former lakebed on Mars. These could be from meteorites or geological processes—but there's also the possibility they are the remnants of ancient Martian life.
Because the core elements of life (C, H, O, N, S, and P) are consistent across all known organisms, the discovery of carbon elsewhere is always intriguing.
3. Miller’s H₂S Volcano Simulation Experiment
In 1958, Miller ran another version of his experiment, this time adding hydrogen sulfide (H₂S) to simulate conditions near early Earth volcanoes. The samples, sealed and forgotten, were analyzed decades later by his former student Jeffrey Bada.
The results showed the presence of 23 different amino acids, including:
Glycine (baseline compound)
Serine
Methionine (contains sulfur)
Alanine
The molar ratios revealed that even trace gases like H₂S could have significantly influenced the variety and abundance of organic molecules produced. In particular, sulfur-containing amino acids like methionine were more likely in the volcanic simulation.
4. Why This Matters
Carbon’s bonding flexibility allows it to form:
Chains
Branches
Rings
Complex three-dimensional structures
This unique chemical versatility underlies the molecular diversity of life, from DNA to enzymes.
In a Nutshell
Carbon is essential for life due to its ability to form four covalent bonds, allowing endless molecular possibilities.
Stanley Miller’s 1953 experiment showed that organic molecules can form abiotically, simulating early Earth conditions.
Later experiments, including one near-volcano simulation, confirmed the abiotic formation of diverse amino acids.
Discoveries of carbon compounds on Mars suggest that the building blocks of life may not be limited to Earth.
All this underscores carbon’s unique role in the chemical foundation of biology.
Practice Questions
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