Lecture 8: What is life? - Life as a chemical system

1. Earth life - basic biochemistry

2. Metabolism

3. Catalysis

4. Genetics

Life’s machinery in a cell

A bacterial cell: RNA moleculestranscribe messages from DNAthat are used to produce proteinmolecules inside ribosomes - Fig.5.1 - A. Knoll (2003).

Structure of DNA & RNA

Molecular structure- Fig.5.2 - A. Knoll (2003).

Lipid bilayer vesicles in clay

RNA (red) adsorbed into clay, inside a vesicle (green) - Szostak lab (2004).

Phylogenetic Tree of Life

Sci

ence

, 200

6

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.