why do protein based and steriod based hormones utilize, respectively, second messenger and intracellular ?
Posted on | September 7, 2010 |
why do protein based and steriod based hormones utilize, respectively, second messenger and intracellular receptor mechanisms of action?
Category: Steriod Questions
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September 7th, 2010 @ 12:00 am
A. Steroid Hormones and Gene Expression. These hormones pass through the target cell and into the nucleus where they bind to a receptor protein. Here they activate certain genes.
B. Peptide Hormones and Second Messengers. They are unable to pass through the plasma membrane and have different methods of action. They attach to their receptors in the target cell surface and influence activity within the cell through cytoplasmic intermediates called second messengers.
The two most important messengers are cAMP and inositol triphosphate.
Cyclic AMP: ATP is converted into cAMP after a series of reactions on the plasma membrane following the attachment of the hormone to the membrane. cAMP relays the signal from the membrane to the metabolic machinery of the cytoplasm.
Inositol Triphosphate: Involves the use of Ca+2 that regulates cellular protein activity.
September 7th, 2010 @ 12:00 am
Because, unlike steroids based hormones, they can’t pass through the plasma membrane. They have to bind a cell surface receptor. This receptor-ligand binding sends a second messenger inside the cell. This second messenger can then act upon other proteins like transcription factors. In contrast, steroids can signal by directly binding and activating a transcription factor.