ABSTRACT
The living cell is an open system characterized by the input and output of energy and matter. Even the very first cells must have been able to harness energy from their environment to survive and reproduce ( Figure 6.1 ). To perform these central functions, they had a whole range of molecular features that can still be found in every living being today, some 4 billion years later – whether you consider a bacterium or an elephant ( Figure 6.2 ), a mushroom, a tree, or us human beings.
