From his experiments, S.L. Miller produced amino acids by mixing the following in a closed flask:

CH4, H2, NH3 and water vapour at 800°C

CH3, H2, NH4 and water vapour at 800°C

CH4, H2, NH3 and water vapour at 600°C

CH3, H2, NH3 and water vapour at 600°C

Miller-Urey Experiment

மில்லர்-யுரே சோதனை

NCERT Class 12 · Evolution · 1 NEET question

Life did not emerge from magic; it emerged from chemistry. Miller-Urey proved that Oparin-Haldane’s hypothesis of chemical evolution is testable. If you think life requires a 'spark' beyond physics, you are failing Biology.

The idea

S.L. Miller created a closed system simulating primitive Earth conditions. He used a mixture of CH4, NH3, H2, and water vapour in a flask at 800°C with electric discharge. This simulated lightning. The experiment resulted in the synthesis of simple amino acids, providing experimental evidence for chemical evolution.

Why it matters

It provides experimental evidence that organic building blocks of life can be synthesized from inorganic precursors under abiotic conditions.

NEET lens

NEET focuses on the specific gases used: CH4, NH3, H2, and water vapour. Do not confuse this with the Oparin-Haldane theory, which is the hypothesis, while Miller-Urey is the experimental proof. Remember the 800°C temperature and the electric discharge setup. This is a high-yield area; expect a direct question on the components used.

Clinical significance

The synthesis of amino acids is the foundation of protein biochemistry. Without the stable formation of these monomers, the translation of genetic information into functional enzymes would be impossible. Metabolic diseases often arise from the failure of these precise molecular structures to fold correctly.

Introduction

In 1953, S.L. Miller showed experimentally that simple organic molecules like amino acids could form from inorganic substances under conditions thought to exist on the primitive Earth.

Core concept

Set-up: a closed flask containing CH4 (methane), H2 (hydrogen), NH3 (ammonia) and water vapour at 800°C; an electric discharge simulated lightning. Result: amino acids were formed. Others observed formation of sugars, nitrogen bases, pigments and fats in similar experiments. This supported the Oparin-Haldane idea that the first forms of life came from pre-existing non-living organic molecules (chemical evolution).

Go deeper

Analysis of meteorite content also revealed similar compounds, suggesting such processes occur elsewhere in space. The primitive atmosphere was reducing — it lacked free oxygen.

From Class 10

Just as lightning can trigger chemical reactions, Miller used electric sparks in a flask to make the building blocks of life.