During the next twenty years Blobel characterized in detail the molecular mechanisms underlying these processes. A number of human hereditary diseases are caused by errors in these signals and transport mechanisms. An adult human being is made up of approximately 100,000 billion cells. A cell contains many different compartments, organelles, each surrounded by a membrane. The organelles are specialized to carry out different tasks.
Every cell contains approximately one billion protein molecules.
The different proteins have a large number of important functions. Some constitute the building blocks for constructing the cell while others function as enzymes catalyzing thousands of specific chemical reactions. The proteins within a cell are constantly degraded and resynthesized. Thus, it was for a long time a puzzle how large proteins could traverse the tightly sealed, lipid-containing, membranes surrounding the organelles. Some decades ago, it was also unknown how newly made proteins were directed to their correct locations in the cell.