A2 Cells Flashcards
What is pre-biotic, and what was it like?
Period on Earth before life existed
Conditions:
- Very little oxygen
- Lots of methane
- Increased carbon dioxide
- Higher temperatures
- No UV protection from atmosphere
- Lots of lightning
Conditions promote spontaneous reactions not currently possible
Spontaneous formation of carbon compounds
Living things changed conditions (like increased oxygen and ozone), so no more spontaneous life forms created
Cells as the smallest units of self-sustaining life
Self-sustaining: using energy to maintain highly-ordered state. Living organisms can pass on this ability to their offspring
Organisms can be unicellular or multicellular
We know organisms are living, but what about smaller components?
Evidence that cells are living:
- Each cell uses energy to maintain order
- Some cells stop doing this and die
- Cells produce more cells
- Cells can live outside of the body in a culture
Smaller cell components cannot do these things
Cell theory
- All living things are composed of cells
- The cell is the smallest unit of life
- A cell must come from a pre-existing cell
What was Pasteur’s experiment?
Falsified spontaneous generation
New cells come from existing cells
Where did the first cell come from? How could non-living things form a living cell
Several things must have happened:
- Catalysis / control over reactions
- Self assembly of polymers
- Compartmentalisation / membrane formation
- Self-replicating molecules
Evidence for the origin of carbon compounds
Miller-Urey experiment
Prebiotic gas mixture and energy
Produced amino acids
Conclusion: carbon compounds arose on Earth before life evolved
What was the Miller-Urey experiment?
A system in which one flask contained a gaseous mixture of ammonia, methane and hydrogen, simulating Earth’s atmosphere, which was connected to a flask of liquid water, simulating the ocean. The water was heated until boiling, producing water vapour, which was directed into the flask with the gaseous mixture. An electric spark was sent through the mixture continuously, simulating lightning. A condenser below the flask allowed the assimilation of an aqueous solution.
This solution was sampled and amino acids were found
