 New students, in this topic we shall discuss hormones and their general properties. The hormones are signaling molecules which are produced by the endocrine glands. They are transported by the blood to their respective target tissues. Students regulate the physiology and behavior of an animal. Dear students, we shall discuss in detail the properties of hormones. The first property of the hormone is that they act on specific target cells or tissues. The specificity of hormonal action depends on the types of receptors. A hormone comes in contact to all types of tissues in the body during circulation. Do you know that when a hormone is made by a gland and it is handed over to the blood, the blood passes through the entire body and it is in contact with all types of tissues. But this hormone acts only on its target cells. This is because of the presence of receptors which are not present with every cell. Only the cells which have these receptors are affected by the hormone. The action of the hormone depends on the nature of the enzyme cascade which is linked to the receptor. The specificity of the receptor is that the chemical reactions that are generated by the receptor are only found in the cells which are kept by the receptor. Moreover, there are receptors but the difference in the enzyme cascade is that a hormone can produce multiple actions. If there are two types of receptors and two different types of tissues for a hormone, then different types of enzyme cascades are also produced as a result of that. This is because some hormones affect more than one tissue but produce different effects. Dear students, hormones are active at very low concentration. The first thing is that endocrine glands produce hormones in a very small quantity. The second thing is that these hormones are circulated through the blood where they are diluted. So for tissues, the available concentration of a hormone lies between 10 raised to power minus 8 to 10 raised to power minus 12 molar. But all in all hormones are still active at this low concentration. The reason for this is that the hormonal actions are amplified because the binding of a hormone to its receptor leads to an enzymatic cascade. This enzymatic cascade has such steps in which the action of the hormone is actually multiplied or amplified. So just a few molecules of a hormone can modulate thousands or millions of molecular reactions within a cell.