Cell Communication II

Chapter 15

An animal cell depends on extracellular signals to survive or divide

An animal cell depends on extracellular signals to differentiate. Without extracellular signals the

cell will die

Signaling molecules must be turned over rapidly; if turnover time is one minute concentration can decrease rapidly

Extracellular signaling molecules can bind to intracellular receptors

Acetyl choline causes release of NO which results in rapid relaxation of smooth muscle cells

Signaling molecules that bind to nuclear receptors are small and hydrophobic

Inhibitory proteins make receptor inactive when not bound to the signaling molecule

When signaling molecule binds receptor binds DNA and increases gene transcription

Nuclear receptors have a DNA binding domain

Extracellular signaling molecules can bind to cell surface receptors

3 large classes of cell surface receptors; ion channel linked receptors

Active Chemical Synapse

3 large classes of cell surface receptors; G protein linked receptors

3 large classes of cell surface receptors; enzyme linked receptors

G-protein linked receptor

The structure of an inactive G-protein

Without signaling molecule G-protein is inactive

G-protein binds to receptor when signaling molecule is present

G-protein accepts GTP and disassemble into two active subunits

The α subunit of the G-protein can be deactivated through hydrolysis of GTP

Deactivation of G-protein

Reassembly of α subunit with other 2 subunits reforms inactive G-protein complex

Arrestin binds phosphorylated G-protein receptor and deactivates the receptor and

prepares it for endocytosis

DVD clip 61

Release of cAMP inside cell caused by serentonin and mediated by a G-protein

Synthesis and degradation of cyclic AMP

Activation of cAMP dependent protein kinase

Activation of gene transcription by cAMP

Activation of gene transcription by cAMP