ABSTRACT
Xenobiotics exert adverse effects through toxicokinetics (TK) and toxicodynamics (TD). Toxicokinetics or pharmacokinetics is a science that indicates the quantitative fate of a xenobiotic in the body whereas toxicodynamics is a process of interaction between active forms of xenobiotics and biomolecules such as DNA, protein, and lipids. Physiological and biochemical processes in the body undergo absorption, distribution, metabolism, and excretion (ADME) of toxicants, which may explain how to predict potential biological Schematic diagram of a biological membrane. Spheres represent head groups (phosphatidylcholine) and lines indicate tail ends of lipids. Black, white, and stippled spheres indicate different kinds of lipids. Large bodies represent proteins; some are located on the surface, others within the membrane. Glycoproteins or glycolipids are attached to proteins and lipids on the surface of cell membrane. (Adapted from Singer SJ, Nicolson GC, <italic>Science</italic>, 175, 720–31, 1972.) https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429225451/dcd28b67-dd36-4e9c-87a1-8f16e51dd5cb/content/fig0001.jpg"/> 24 activities. Absorption, the first step of TK, can be defined as systematical entry of xenobiotics into the body via the bloodstream. Metabolism (bio-transformation) will be discussed separately in Chapter 3. A xenobiotic needs to pass through various membranes to be absorbed, distributed, and excreted. A cell membrane generally consists of a biomolecular layer of lipid molecules with proteins scattered throughout the membrane (Figure 2.1).
