Date post: | 31-Dec-2015 |
Category: |
Documents |
Upload: | vivien-wilson |
View: | 219 times |
Download: | 3 times |
Cell Communication
Chapter 11
• Cells need to communicate between themselves to maintain homeostasis.
• Process by which signal on cell’s surface converted into specific cellular response consists of series of steps - signal-transduction pathway.
• Yeasts communicate between 2 types of yeast cells to reproduce.
• 2 sexes, a and alpha - secrete specific signaling molecule, a factor and alpha factor.
• Factors find each other and bind to each other’s receptors.
• Also occurs in multicellular organisms.
• Some cells release local regulators - influence cells in local vicinity.
• Synaptic signaling - nerve cell produces neurotransmitter that diffuses to single cell - is almost touching sender.
• Nerve signals travel along series of nerve cells without unwanted responses from other cells.
• Plants, animals - hormones to signal at greater distances.
• Cells may communicate by direct contact.
• Signaling substances dissolved in cytosol pass freely between adjacent cells.
• 3 stages to signal transduction. • 1Reception - chemical signal
binds to cellular protein at cell’s surface.
• 2Transduction - binding leads to change in receptor that triggers series of changes along signal-transduction pathway.
• 3Response - transduced signal triggers specific cellular activity.
• Receptor proteins present on cells to recognize signal molecules.
• Ligand - molecule that binds to another molecule, causes cell to change shape when attached to cell’s receptor.
• Receptors usually found on plasma membrane since signals can’t pass through membrane.
• 1 type - G-protein-linked-receptor.
• Acts as on/off switch; cycles between being active and inactive.
• Tyrosine-kinase receptor system helps different systems to function at same time.
• System activated - activates other systems at same time.
• Ligand-gated ion channels open/close to allow chemical signals to pass through.
• Important in nervous system - allow Na+ and K+ move into and out of cell.
• Some signals diffuse through plasma membrane; don’t need proteins.
• Some are hormones which act on transcription process.
• Transduction stage of signal pathway allows for small signal to be amplified - causes large signal.
• Protein kinases essential - help to initiate responses.
• Response of particular cell to signal depends on particular collection of proteins.
• Some pathways actually linked by scaffolding proteins - allows signals to be passed through pathways.