Understanding:
• The first cells must have arisen from non-living material
The theory that living cells arose from non-living matter is known as abiogenesis
This process is theorised to have occurred over four key stages:
- There was non-living synthesis of simple organic molecules (from primordial inorganic molecules)
- These simple organic molecules became assembled into more complex polymers
- Certain polymers formed the capacity to self-replicate (enabling inheritance)
- These molecules became packaged into membranes with an internal chemistry different from their surroundings (protobionts)
Miller-Urey Experiment
The non-living synthesis of simple organic molecules has been demonstrated by the Miller-Urey experiment
Stanley Miller and Harold Urey recreated the postulated conditions of pre-biotic Earth using a closed system of flasks and tubes
- Water was boiled to vapour to reflect the high temperatures common to Earth’s original conditions
- The vapour was mixed with a variety of gases (including H2, CH4, NH3) to create a reducing atmosphere (no oxygen)
- This mixture was then exposed to an electrical discharge (simulating the effects of lightning as an energy source for reactions)
- The mixture was then allowed to cool (concentrating components) and left for a period of ~1 week
- After this time, the condensed mixture was analysed and found to contain traces of simple organic molecules
Overview of the Miller-Urey Experiment
