 It has been estimated that average @-@ sized bacteria contain about 2 million proteins per cell ( e.g. E. coli and <unk> <unk> ) . Smaller bacteria , such as <unk> or <unk> contain fewer molecules , namely on the order of 50 @,@ 000 to 1 million . By contrast , eukaryotic cells are larger and thus contain much more protein . For instance , yeast cells were estimated to contain about 50 million proteins and human cells on the order of 1 to 3 billion . Note that bacterial <unk> encode about 10 times fewer proteins than humans ( e.g. small bacteria ~ 1 @,@ 000 , E. coli : ~ 4 @,@ 000 , yeast : ~ 6 @,@ 000 , human : ~ 20 @,@ 000 ) . 
