Question

Give an account of the Miller and Urey experiment on the origin of life.

Answer 1

The Miller and Urey experiment (1953) was a classical laboratory experiment designed to test the Oparin-Haldane hypothesis of the abiotic origin of biomolecules under primitive Earth conditions.

Purpose:

To demonstrate the abiotic synthesis of organic compounds, including amino acids, from simple inorganic molecules thought to be present in the early Earth’s reducing atmosphere.

Setup:

1. A closed apparatus was used consisting of two flasks connected by tubes and a condenser.
2. One flask contained water, which was boiled to produce water vapor representing the primitive ocean.
3. The water vapor entered a second flask containing a mixture of gases simulating the primitive atmosphere: hydrogen (H₂), methane (CH₄), ammonia (NH₃), and water vapor (H₂O).
4. Electric sparks were discharged between tungsten electrodes in the gas flask to simulate lightning, providing energy for chemical reactions.
5. The gases and sparks reacted in the flask; then, the vapor passed through a condenser, cooling and collecting any formed compounds in liquid form.

Conditions:

• Temperature in the liquid flask was maintained by heating to generate water vapor.
• Electric sparks were applied continuously for several days.

Results:

• After running the experiment for a few days, the liquid in the apparatus was analyzed.
• Miller and Urey found that several amino acids (such as glycine, alanine, and aspartic acid) and other complex organic compounds had formed spontaneously from the simple gases.
• This showed that organic molecules necessary for life could be synthesized abiotically under the conditions simulating the early Earth’s atmosphere.