Origins of cells

Prebiotic Earth Conditions

no oxygen, intense UV radiation, high methane and CO₂ levels—ideal for spontaneous formation of organic molecules like amino acids.

a Cell

Cells are the smallest units of life; they are self-sustaining, maintain order, can reproduce, and live outside organisms.

Spontaneous Generation

Louis Pasteur disproved the idea that life could arise spontaneously; today, cells only arise from pre-existing cells.

Requirements for the First Cell

The first cell needed metabolism, polymer formation (e.g., proteins, DNA), compartmentalization, and self-replicating molecules.

Miller-Urey Experiment

Simulated prebiotic Earth conditions showing that amino acids, the building blocks of life, could form spontaneously.

Formation of Membranes

Phospholipids spontaneously form bilayers in water, creating vesicles, which are key for compartmentalization and selective permeability.

RNA as First Genetic Material

RNA likely preceded DNA as it is self-replicating, catalytic, mutates quickly, and is found in RNA-only viruses.

LUCA – Last Universal Common Ancestor

All life likely descended from LUCA, evidenced by shared use of DNA and similar ribosomes.

Dating the Origin of Life

Carbon dating suggests LUCA arose ~4.1 billion years ago; genomic comparisons suggest ~4.5 billion years ago.

Possible Location of LUCA

Genes common to all life hint that LUCA lived in extreme environments like hydrothermal vents rich in CO₂, H₂, and minerals.