| A | B |
|---|
| AIDS | acquired immunodeficiency syndrome, the disease that results when the HIV virus attacks the human immune system |
| allergy | a condition in which a person's immune system is overly sensitive to environmental substances that are normally harmless |
| antibodies | a protein, produced by the immune system, that either attacks invading pathogens or marks them for killing |
| antigen | a molecule found on the outer surfaces of cells that the immune system recognizes as either part of the body or an outside invader |
| ATP | adenine triphosphate, a compound that stores energy in cells |
| bacteria | any one of many single-celled oranisms without a distinct nucleus, a prokaryote cell |
| biochemical processes | a chemical process that occurs in a living thing |
| catalyst | a substance that can speed up the rate of a chemical reaction, without being changed or used up during the reaction |
