facilitated transport, where a specialized protein molecule, called a carrier,
carries a water-soluble substance across the membrane
active transport, which requires both a carrier and energy
Of the four mechanisms, active transport is the only one where a toxicant
can move against a concentration gradient, i.e., move from a low-concentration compartment to a high-concentration compartment (Table 4.1). This
accounts for the need for energy expenditure.
4.3.3 TRANSPORT
Immediately after absorption, a toxicant may be bound to a blood protein
(such as lipoprotein), forming a complex, or it may exist in a free form. Rapid
transport throughout the body follows. Transport of a toxicant may occur
through the bloodstream or lymphatic system. The toxicant may then be
distributed to various body tissues, including those of storage depots and sites
of metabolism.
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Ref: 4365 MING-HO YU Chap-004 Page: 50 45-64
FIGURE 4.3 Processes of poisoning in animals and humans.