Cell Communcation

• A signal transduction pathway is a series of steps which converts a signal on a cell's surface to a specific cellular response
• Quorum sensing is the ability of bacteria to sense the local concentration of other bacteria
• Animal cells may communicate via direct contact between membrane-bound cell surface molecules i.e. cell-cell recognition
• Paracrine signalling is when cells simultaneously receive and respond to molecules secreted by another cell
• Synaptic signalling occurs in the nervous system
• Hormones are used for long distance signalling. In animal cells, specialized cells release hormone molecules which travel via the circulatory system to target other cells. In plants, plant growth regulators travel through vessels or by diffusion.
• The 3 stages of Cell Signalling are:

  1. Reception: The target cell detects the signalling molecule via a receptor
  2. Transduction: The binding causes changes in the receptor initiating signal transduction
  3. Response: The transduction signal triggers a specific cellular response
• Extracellular receptors include G protein-couple receptors, receptor tyrosine kinases, and ion channel receptors. Intracellular receptors can be found in the cytoplasm or nucleus and are small and / or hydrophobic.