receptors

• reception

  • detection by cell of signal (usually from outside)
  • signal molecule interacts directly with receptor on surface/inside cell
  • receptor binding
• ligand 


  small molecule that binds to a larger one
• ligand binding can cause change in shape of protein or aggregation of 2 or more receptors
• hydrophobic messengers can 


  move through lipid environment, signal receptors can be inside cell
• receptors in plasma membrane

  • G protein coupled receptors
  • receptor tyrosine kinases
  • ion channel receptors
• G protein coupled receptors

  • largest family of receptors
  • spans membrane as seven alpha helices
  • use G protein
• G protein

  • bind guanine nucleotides
  • GTP and GDP
  • molecular switch
  • GDP bound- switch is off
  • GTP bound- switch on
• natural state of G protein is to have GDP bound, needs GTP to displace and activate G protein
• adrenaline from adrenal gland function

  stimulates glycogen breakdown in liver and skeletal muscle during stress
• diseases that affect G proteins

  • Whooping cough
  • Cholera
  • Botulism
• receptor tyrosine kinases

  • intrinsic enzyme activity (are enzymes themselves)
  • add phosphate residues onto other proteins
  • trigger multiple pathways simultaneously
• receptor tyrosine kinase

  • 2 monomers associate with each other
  • forms complex (dimer)
  • activates tyrosine kinase on each monomer
  • each adds phosphate from ATP
  • activated receptor, recognised by specific relay protein
  • relay protein binds to specific phosphorylated tyrosine
• RTKs associated with 


  growth factors
• abnormal function of RTKs is associated with many types of

  cancer
• ligand gated ion channel

  • pore that can open or close
  • molecule binds, receptor allows specific ions through
• ligand gated ion channels e.g.

  neurotransmitters
• verapamil 


  calcium channel blocker (hypertension, cardiovascular disorders)
• lamictal


  sodium channel blocker (epilepsy)
• lidocaine 


  sodium channel blocker (local anaesthetic)
• glipizide 


  potassium channel blocker (diabetes)
• intracellular receptors

  • in cytosol/nucleus
  • small/hydrophobic chemical messengers
  • can act as transcription factor