Knowledge Check Solutions
1) Absorption - This is the correct answer.
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.
2) Pass through several cell membranes - This is the correct answer.
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.
3) A bilayer of phospholipids with scattered proteins within the layers - This is the correct answer.
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.
4) Simple diffusion - This is the correct answer.
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.
5) Pinocytosis - This is the correct answer.
Pinocytosis (cell drinking) involves the engulfing of liquids or very small particles that are in suspension within the extracellular fluid.
1) Absorption - This is the correct answer.
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.
2) Pass through several cell membranes - This is the correct answer.
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.
3) A bilayer of phospholipids with scattered proteins within the layers - This is the correct answer.
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.
4) Simple diffusion - This is the correct answer.
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.
5) Pinocytosis - This is the correct answer.
Pinocytosis (cell drinking) involves the engulfing of liquids or very small particles that are in suspension within the extracellular fluid.