The process whereby a substance moves from outside the body into the body is known as:
Correct! Absorption is the first and crucial step in the toxicokinetics of a xenobiotic. Without absorption, a toxic substance does not represent a human health hazard.
Incorrect! Absorption is the first and crucial step in the toxicokinetics of a xenobiotic. Without absorption, a toxic substance does not represent a human health hazard.
For a xenobiotic to move from outside the body to a site of toxic action requires that it:
Correct! In order for a xenobiotic to move from outside the body to an internal site of toxic action (target cells), a xenobiotic must pass through several membrane barriers. The first membranes are those at the portal of entry, for example, lung or intestinal tract.
Incorrect! In order for a xenobiotic to move from outside the body to an internal site of toxic action (target cells), a xenobiotic must pass through several membrane barriers. The first membranes are those at the portal of entry, for example, lung or intestinal tract.
The basic structure of the cell membrane consists of:
Correct! The typical cell membrane consists of two layers of phospholipids with polar head groups consisting of phospholipid molecules and the lipid inner portion consisting primarily of cholesterol molecules. The phospholipid layers are oriented on opposing sides of the membrane so that they are approximate mirror images of each other. Various proteins are scattered throughout the lipid bilayers of the membrane.
Incorrect! The typical cell membrane consists of two layers of phospholipids with polar head groups consisting of phospholipid molecules and the lipid inner portion consisting primarily of cholesterol molecules. The phospholipid layers are oriented on opposing sides of the membrane so that they are approximate mirror images of each other. Various proteins are scattered throughout the lipid bilayers of the membrane.
The membrane transport process by which large hydrophobic molecules cross membranes via the lipid portion of the membrane, follow the concentration gradient, and do not require energy or carrier molecules is known as:
Correct! Large hydrophobic molecules must diffuse through the lipid portion of the membrane, with the rate of transport correlating with its lipid solubility. In general, highly ionized chemicals have low lipid solubility and do not readily pass through the lipid membrane.
Incorrect! Large hydrophobic molecules must diffuse through the lipid portion of the membrane, with the rate of transport correlating with its lipid solubility. In general, highly ionized chemicals have low lipid solubility and do not readily pass through the lipid membrane.
Endocytosis is a form of specialized membrane transport in which the cell surrounds the substance with a section of its cell membrane. The specific endocytosis process by which liquids or very small particles are engulfed and transported across the membrane is known as:
Correct! Pinocytosis (cell drinking) involves the engulfing of liquids or very small particles that are in suspension within the extracellular fluid.
Incorrect! Pinocytosis (cell drinking) involves the engulfing of liquids or very small particles that are in suspension within the extracellular fluid.