1. Lecture 10: What is life? - Its Origins

2. Life’s machinery in a cell A bacterial cell: RNA molecules transcribe messages from DNA that are used to produce protein molecules inside ribosomes.

3. Structure of DNA

4. Earth life - main attributes: 1)life is chemical in essence; an ordered network of chemical reactions; 2)life is energy dissipating; out-of-equilibrium system; 3)life is compartmentalized; 4)life is adaptive, self-optimizing, fed back, forward; stable to perturbations; 5)life uses molecules that are suited to water.

5. DNA RNA proteins Structure and function replication processing Organizational Complexity of Modern Life

6. RNA biochemical functions An earlier, simpler time:

7. Between non-life and life… Viruses Protocells Self-replicating nucleic acids

8. What do we know about the Origin of Life? From G.F. Joyce, 2002, Nature 418: 214-221

9. From Chemistry to Biology? small molecules (CO, H 2, H 2 0, NH 3, CH 4 …) + energy lipids + sugars + nucleobases + high-energy + amino acids compounds Self-assembly into vesicles activated nucleotides Assembly into genetic polymer peptides cofactors protocell?

10. The simplest protocell requires a membrane for compartmentalization, a replicating genome, and a source of nucleotides and lipids. Mechanical energy (for division), chemical energy (for nucleotide activation), and possibly osmotic gradient energy (for growth) may be used by the system. Model of Simple Protocell Matter and Energy Fluxes

11. The RNA World: Pre-biotic RNA formation Janet Iwasa/ Szostak Lab

12. The RNA World: Formation of Vesicles Janet Iwasa/ Szostak Lab

13. Why life needs a membrane compartment Janet Iwasa/ Szostak Lab

14. The RNA World: Protocell life cycle & division Janet Iwasa/ Szostak Lab

15. Lipid bilayer vesicles in clay RNA (red) adsorbed into clay, inside a vesicle (green) - Szostak lab (2004).

16. Earth life - main attributes: 1.life is chemical in essence; an ordered network of chemical reactions; 2.life is energy dissipating; out-of-equilibrium system; 3.life is compartmentalized; 4.life evolves by natural selection and inheritance of variation 5.life evolves to be adaptive, self-optimizing, fed back, forward; stable to perturbations; 6.Earth life uses molecules that are suited to water.