CHAPTER 9 (b) - HORMONES

HORMONES
-endocrine system is made u of ductless glands
-that release certain chemicals that deliver messages throughout the body
-can effect almost every cell in the body
-called hormone
-hormones are chemical released in one part of the body that travels through bloodstream
-they affect by binding to specific chemical receptor on those cells
-cells that have receptor for a particular hormone are called target cells
-response of the body to hormones are slower and long lasting
-because they are secreted as a steady trickle into the bloodstream
-hormones influence the metabolism of cells , growth and development of body parts

18 SX

MECHANISM OF ACTION OF STEROID AND NON STEROID HORMONES

-hormones fall into two group of compound
-some hormones are steroids
-other hormones are non-steroid
-these two group of hormones have different mechanism of action against on target cells
-the mechanism by which a hormone depends mainly on whether its receptor molecules is within
-or on the surface of the target cells

1. Steroid hormones move through the membrane to activate specific genes, causing protein synthesis

2. Non steroid hormones bind to membrane receptor, activating proteins in the cytoplasm

MECHANISM OF STEROID HORMONES ACTION VIA GENE ACTIVATION

1. Some hormones such as steroid hormones are lipid soluble , so they can enter easily through the phospholipid layer of the cell surface membrane
2. In the cytoplasm or in the nucleus , the hormones bind to its receptor to form a hormone-receptor complex
3. The hormone receptor complex then bind to a specific section of DNA which functions as gene
4. The complex stimulates the gene to transcribe messenger RNA (mRNA)
5. The mRNA moves to the cytoplasm and directs the synthesis of protein that alter the activity of the cells

SECOND MESSENGER ( cAMP ) MECHANISM BY NON-STEROID HORMONE

-Non steroid hormone
-peptide and amino based hormone are soluble in water but not in lipid
-they cant penetrate through the plasma membrane

enzyme phosphorylase kinase
1.HORMONE@ FIRST MESSENGER bind to receptor in plasma membrane
2.Form hormone receptor complex
3.Hormone receptor complex then bind and activate Gprotein
4.Then the G protein bind to the enzyme adenylyl  cyclase and activates it
5.Activated adenylyl cylase catalyst the conversion of ATP to AMP
6.CAMP@SECOND MESSENGER , initiates a complex chain reaction
7.CAMP activates the enzyme protein kinase which activate enzyme phosphorylase kinase
8.The active phosphorylase kinase activates the enzyme glycogen
9.That catalyse the breakdown of glycogen to glucose phosphate
10.This chain reaction is called a cascade effect where the action of enzyme in turn activates
another enzymatic reaction producing many product molecules