The cytoplasm surrounds the nucleus and is enclosed by the plasmalema.
The fluid cytoplasm (or cytosol) bathes metabolically active structures called organelles.
They may be membranous (such as mitochondria) or nonmembranous protein complexes (such as ribosomes and proteasomes).
Most organelles are positioned in the cytoplasm by movements along the polymers of the cytoskeleton, which also determines a cell’s shape and motility.
Cytosol also contains hundreds of enzymes, such as those of the glycolytic pathway, which produce building blocks for larger molecules and break down small molecules to liberate energy.
Oxygen, CO2, electrolytic ions, low-molecular-weight substrates, metabolites, and waste products all diffuse through cytoplasm, either freely or bound to proteins, entering or leaving organelles where they are used or produced.
Cytoplasmic structures comprise three groups.1