Cell Signalling

• what is meant by cell signalling?

  • the communication between cells
  • used in cell recognition, allows cells to work together/coordination between action of different cells, and to trigger responses/reactions
• what is an Agonist?

  a drug that binds to the receptor and produces a similar response to the intended chemical and receptor
• what is an Antagonist?

  a drug that binds to the receptor and stops the receptor from producing a response (e.g. beta blockers - used to reduce the response of the heart to stress, they act by binding to cell receptors)
• how do cells signal each other?

  by direct contact or via messengers such as neurotransmitters and hormones
• what is the structure of a transmembrane receptor?

  • extracellular domain - where messenger binds
  • transmembrane domain - middle
  • intracellular domain - relays signal to the cell by signal transduction (message is translated)
• what do G-protein coupled receptors allow to signal across them?

  • neurotransmitters (dopamine and serotonin)
  • hormones (adrenaline and noradrenaline)
  • chemicals involved in inflammation
• how do G-protein coupled receptors work?

  • neurotransmitter (or hormone etc) binds to receptors extracellular domain and send a signal to the G-protein
  • activation of an intermediate protein called a G-protein - this can then influence the opening of ion channels, affect enzymes and activate intracellular signalling molecules known as second messengers (which can initiate signalling cascades within cell)
  • have a slower action but have more widespread effects
• what do ligand gated channel proteins allow through/across them?

  • neurotransmitter acetylcholine
• how do ligand gated channel proteins work?

  • neurotransmitter binds to binding site
  • causes a channel to open in the receptor
  • ions are permitted to flow into neuron
• what is the neurotransmitter that binds to a ligand gated channel protein know as?

  a ligand (any substance that can bind to a target protein)
• what do cotransporter proteins allow to move through/across them?

  • moving sucrose into a companion cell (H+ ions and sucrose both have to bind to the channel protein)
• how do Cotransporter proteins work?

  • 'ligand-like' molecule has to move through protein WITH the desired molecule
  • no binding