From Bill Bryson's "A Short History of Nearly Everything", talking about a cell in the human body:
Typically a cell will contains some twenty thousand types of protein, and of these about two thousand types will be represented by at least fifty thousand molecules. 'This means,' says Nuland, 'that even if we count only those molecules present in more than 50,000 each, the total is still a very minimum of 100 million protein molecules in each cell. Such a staggering figure gives some idea of the swarming immensity of biochemical activity within us.'In a single cell. Wow.