ch 16 Flashcards
Describe the signal transduction process for steroid hormones, such as cortisol and sex hormones, from detection of the signal by a cell to the alteration of gene expression
cortisol crosses the plasma membrane of a target cell and binds to its receptor protein in the cytosol , the receptor-hormone complex is then transported into the nucleus via nuclear pores, cortisol binding activates the receptor protein which is then able to bind to specific regulatory sequences in DNA and activate or repress the transcription of target genes
Explain how small, monomeric G-proteins like Ran and Ras can cycle between active and inactive states.
the alteration of the alpha subunit of the G protein allows it to exchange its gdp for gtp, putting it in an active state. To switch to its inactive state, the alpha subunit hydrolyzes its bound gtp to gdp
Describe the signal transduction process for a signal that is received by a G-protein coupled receptor(GPCR) from detection of the signal to the activation of an effecter molecule such as adenyl cyclase
Binding of an extracellular signal molecule to the receptor changes the conformation of the receptor, which in turn alters the conformation of the bound G protein. The alteration of the alpha subunit of the G protein allows it to exchange its GDP for GTP, which triggers an additional conformational change that activates the alpha subunit and the beta-gamma complex, which dissociate to interact with their preferred target proteins in the PM
Define the term ‘second messenger’, and explain their role in signal transduction
messenger molecules created from enzymes; bind to specific signaling proteins in the cell and influence their activity
Describe the signal transduction process that leads to release of calcium ions in the ER
the cleavage of a membrane inositol phospholipid by phospholipase C generates two second messenger molecules: IP3 and DAG. IP3 binds to and opens CA2+ channels that are embedded in the ER, which allows for the CA2+ stored in the ER to flow into the cytosol through the open channels.
Describe the signal transduction process for a signal that is received by a receptor tyrosine kinase (RTK) from detection of the signal to the activation of MAP kinase.
An adaptor protein docks on a particular phosphotyrosine on the activated receptor, the adaptor recruits a Ras-GEF. The activated Ras protein activates a three-kinase signaling module which relays the signal onward which activates MAP kinase.
Explain how signals can be amplified as they move through a signaling pathway
Signals can be amplified by moving through the signaling pathways via a combination of secondary messengers
