Mechanism of Hormone Action

Mechanism of Hormone Action : Gene Activation

• Lipid soluble hormones such as steroids pass through plasma membrane easily.
• In the cytoplasm or nucleus, the hormone binds to its receptor to form hormone-receptor complex.
• The hormone-receptor complex binds to specific part of DNA.
• Transcription occurs to produce mRNA.
• mRNA diffuse out of nucleus & binds to ribosome. Translation occurs. Specific proteins are synthesised.
• Complete proteins carry out specific functions.

Mechanism of Hormone Action : Second Messenger(cAMP) using adrenaline hormone.

• Hormones such as adrenaline are first messengers.
• In the plasma membrane, hormone binds to its receptor to form hormone-receptor complex.
• The hormone-receptor complex binds to G-protein(guanine nucleotide-binding protein) & activates it.
• G-protein binds to enzyme adenylyl cyclase & activates it.
• Adenylyl cyclase catalyses conversion of ATP to cAMP(cyclic adenine monophosphate). cAMP is second messenger.
• cAMP activates enzyme protein kinase which activates enzyme phosphorylase kinase. This stimulates another enzymatic reaction that in turn produces the 'cascade effect'.