Table 1.

Features of major subcellular compartments that affect the intracellular distribution pattern of small chemicals.

Major subcellular compartments	Major biological function	Morphological features	Physiological features	General mechanisms of accumulation
Lysosomes & endosomes	Degradation of excessive cellular proteins, lipids and organelles	Membrane-bound, vesicles	Acidic luminal environment (pH<6) Contain unique, lysosomal protease and hydrolyses.	Active transport; ion trapping; interaction with organelle resident proteins; receptor endocytosis; fluid phase pinocytosis; intracellular membrane trafficking.
Mitochondria	Energy conversion and storage of calcium ions	Membrane-bound, with internal membrane structure	Negative membrane potential. Weakly basic luminal pH (~8). Two membranes. Contain DNA.	Active transport; trapping by chemoelectrical potential; interaction with mtDNA andorganelle resident proteins
Nucleus	Storage of genetic materials	Membrane-bound with large protein pores	Composed of phosphate-rich DNA, RNA, and a large variety of proteins	Active transport; partitioning to nuclear envelope; interaction with DNA, RNA (nucleolar) and organelle resident proteins
Plasma membrane	Separation of the cytosol form the outside environment	Membrane protein-rich phospholipid bilayer membrane	Fluid mosaic, lipid bilayer with selective permeability.	Lipophilic partitioning; absorption to phospholipids; interaction with membrane proteins
Endoplasm reticulum	Facilitation of protein folding and transport of synthesized proteins	Interconnected network of membrane tubules.		Intracellular membrane trafficking; interaction with phospholipids or organelle resident proteins
Golgi apparatus	Process and package of macromolecules	Stacks of semicircular or planar membrane-bound compartments		Intracellular membrane trafficking; interaction with phospholipids or organelle resident proteins
Cytosol		Intracellular solution-like matrix		Interaction with cytosolic components such as the cytoskeleton