*URGENT* list the steps of peptide hormone action
2 answers:
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Hormones are the secretory product of endocrine glands, which are special group of cells or organs. Hormones are released directly into the blood stream to be carried to the other parts of the body, where they affect the target cells. They are organic molecules whose minute quantity can effect majorly on organism's activity. Hormones can be divided chemically into following categories,
- Peptide Hormones, They occur as short chain of amino acids or as long chain of amino acid. Examples, ADH, Oxytocin etc are short chain peptide hormones and Glucagon, insulin, Prolactin etc are long chain peptide hormones.
- Modified amino acid Hormones, Few hormones consists of modified amino acids. Examples, Thyroxine, Epinephrine, Norepinephrine.
- Steroid Hormones, These are lipid in nature hormones. Examples are Oestrogen, Progesterone, Testosterone, Aldosterone, etc.
There are generally two main models to explain the hormone action. One is for the peptide hormone action and the second is for the Steroid hormone action. Both the models have a common first step, following are the steps,
- target cells have specific receptors in their plasma membrane, the structure of receptor has complimentary relationship with the specific hormone. Thus a cell will respond to a hormone only if it possesses the appropriate receptor.
- The receptor molecule is linked with an enzyme, the adenylate cyclase on the inner side of the plasma membrane. The hormone receptor binding turns SLOW ADENYLATE CYCLASE into active form which converts ATP into ADENOSINE MONOPHOSPHATE (Cyclic AMP) in the cytoplasm. The Cyclic AMP serves as second messenger. It then activates specific enzymes which about the appropriate response within the cell. there are several other second messengers as well.
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