The hormones that are derivatives of amino acids, polypeptides or proteins are called peptide hormones. These being insoluble in lipids can not enter the target cell.
These act at the surface of target cell as primary messengers and bind to the cell-surface receptor forming the hormone-receptor complex.
It involves following steps
(i) Hormone called first messenger attaches to the cell surface receptor protein on the outer surface of plasma membrane of the target cell, forming a hormone-receptor complex.
(ii) This complex activates the enzyme adenyl cyclase.
(iii) Adenyl cyclase catalyses the conversion of ATP to cyclic AMP on the inner surface of plasma membrane.
(iv) cAMP serves as the second messenger or intracelluar hormonal mediator delivering information inside the target cells. This activates appropriate cellular enzyme system by cascade effect. Which induces the cell machinery to perform its specialised function.
(v) cAMP has a very short existence. It is rapidly degraded by the cAMP phosphodiesterase. Water soluble hormones, such as amines, peptides, proteins and glycoproteins exert their control through the cyclic AMP. These are quick acting hormones and produce immediate effect.
On an educational trip to Uttaranchal, Ketki and her friends observe that many local people were having swollen necks, Please help Ketki and her friends to find out the solutions to the following questions.
(a) which probable disease are these people suffering from?
(b) How is it caused?
(c) What effect does this condition have on pregnancy?
(a) People with swollen necks are suffering from goitre due to deficiency of iodine in the their bodies.
(b) Iodine is essential for the synthesis of thyroid hormones- $T_3$ and $T_4$ which are iodinated forms of tyroxine. Deficiency of iodine in our diet results in hypothyroidism and enlargement of the thyroid gland occurs place.
(c) Hypothyroidism during pregnancy causes defective development and abnormalities in growing baby like stunted growth (cretinism) mental retardation, low intelligence quotient (IQ) abnormal skin, deafmutism, etc.
Jet lag is caused by the disruption of the body clock as it is out of synchronisation because of the unfamiliar time zone of the destination. The body experiences different patterns of light and dark conditions than it is normally used to, which disrupts the natural sleep-wake cycle.
Melatonin is a hormone that plays a key role in body rhythms and causes jet lag. After the sun sets, eyes perceive darkness and alert the hypothalamus to begin releasing melatonin, which promotes sleep. Conversely, when the eyes perceive sunlight, they tell the hypothalamus to withhold melatonin production.
However, the hypothalamus can not readjust its schedule instantly and it may take several days, to overcome this problem.
Glucocorticoids, particularly cortisol, produce anti-inflammatory reactions and suppress the immune response. The source for glucocorticoids is the middle zone, which is the widest of three zones, in adrenal cortex called zona fasciculata.
The functions of glucocorticoids as the name suggests they is that they affect carbohydrate metabolism and metabolism of proteins and fats. They stimulate gluconeogenesis, lipolysis and proteolysis.
They also inhibit cellular uptake and utilisation of amino acids. Cortisol is also called stress hormone as it copes with stress.