Change nature of the cell longer lasting effect

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Change nature of the cell (Longer-lasting effect) Modulation of signal effect • Priming (upregulation) Signal bindsÆ more receptors synthesized Ø more hormone can bind cell • Desensitization (downregulation) Prolonged exposure to high signal molecule levels can reduce receptor expression. * Downregulation may be avoided by pulsatile secretion of the messenger. • Receptor-mediated endocytosis Receptor-ligand complex internalized on vesicle to enhance duration of effect. Electrochemical communication Mechanisms of Messenger Action • Hydrophilic signal molecules — most amino acid class – Bind to membrane receptors on cell surface – Primary effect: turn enzymes on/off Æ D activity of cell. – Secondary effect: enzymes may produce or activate transcription factors Æ turn genes on/off. • Lipophilic signal molecules — steroids & thyroid hormones – Bind to intracellular receptors in cytoplasm or nucleoplasm – Primary effect: turn genes on/off Æ D nature of cell. – Secondary effect: gene expression may produce or...
View Full Document

This note was uploaded on 09/02/2011 for the course BIOL 6a taught by Professor Staff during the Fall '10 term at DeAnza College.

Ask a homework question - tutors are online