Abstract:  Simple cells like bacteria are mostly protein.  So, it is reasonable to expect that some physical behaviors of cells are attributable to the properties of their proteome, the collection of all of a cell’s proteins.  We explore how cellular growth rates depend on physical properties.  For example, why cells are so sensitive to temperature?  Why are cells so densely packed with proteins?  How does oxidation, which causes increasing cell damage with age, affect the proteome?   Why can’t bacteria duplicate in less than about 20 minutes?  And, what evolutionary factors matter for a cell’s energy balance?