Streaming Proteins

Changing representation of the organism

Static Organism

Until the beginning of the twentieth century the human organism was conceived as an engine immersed in its own liquid environment. It was assumed that all engine constituents exist as long as the organism does. Only the watery envelope turns over, maintaining a steady state that is called homeostasis.

Random turnover

The first experiments with radioactive isotopes that were introduced in the 1930's revealed that all molecules of the organism continuously turn over and are randomly replaced with new ones. In spite of this, microscopic constituents, e.g. cells and tissues, were assumed to be permanent and replaced only when damaged.

Oriented turnover

The 1950s revealed that molecular turnover is not at all random. Molecules are replaced according to the fi-fo rule (first in, first out). The first that are incorporated are also the first to leave, which was first demonstrated in protein synthesis. The protein starts its existence when its DNA code is translated into RNA that serves as template for the assembly of amino acids into short protein chains that grow with time and stream away from the nucleus. They stream through sub-microscopic cavities of the endoplasmic reticulum toward the cell periphery where they are secreted. The protein is born near the nucleus and ages while streaming. Its age may be read off its position in the cytoplasm, the more distant it is from
the nucleus the older it gets.

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