Self-Sustaining Chemical Systems:
As in bacteria, the cytoplasm of eucaryotes is a 20% aqueous protein
solution, containing dissolved ions, small molecules, and many enzymes.
In eucaryotic cells, cytoplasm also is the suspension medium for
the nucleus, mitochondria, and other organelles.
It is a viscous fluid with some degree of structure. Filaments 40
in diameter and 200--diameter
microtubules can be seen anchoring various organelles to one another.
Many important chemical reactions take place in the cytoplasm, including
glycolysis as far as pyruvate, gluconeogenesis from phosphoenolpyruvate
back to glucose, fatty-acid synthesis from acetyl coenzyme A, biosynthesis
of the amino acids that the cell can make (this varies from one
organism to another), synthesis of porphyrin and other organic molecules,
and the priming of tRNA with amino acids for protein synthesis.