Read the summary and the most important questions on Chemical aspects

• 1 Taste perception

• 1.1 Introduction

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• What do non-volatile and volatile molecules have to do with flavour?

  • Non-volatiles --> tastants, molecules inducing these taste sensations (bitter, salty, sweet, sour and/or umami)
    
  • Volatiles --> odours, released from the product enter the nasal cavity
  • directly via the nose
  • indirectly via the oral cavity (retro-nasal)

• Which compounds can decrease bitterness?

  • Masking agents --> binds the bitter tastant and prevents it from contracting the bitter receptor
    
  • Blockers --> binds the bitter receptor and occupies the spot of the bitter tastant

• 1.2 Taste receptors

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• Which 3 papillae exist, where they are located and how many taste buds they contain?

  • Circumvallate --> back of the tongue --> thousands of taste buds
    
  • Foliate --> posterior lateral edge --> hundreds of taste buds
  • Fungiform --> anterior two-thirds of the tongue --> few taste buds

• What is the site of interaction with tastants?

  The 'taste pore'. Microvilli are projected by TRCs to the apical surface of the taste bud. It is the top of the taste bud.

• Which 2 views are there on how taste modalities are perceived by TCRs and how signals are transported through neurons?

  • Labelled-lines model 
  • Across-fibre model

• What is the labelled-lines model?

  Each TRC only contains the receptors for one of the five basic taste modalities. All TCRs for a particular taste in one taste bud combine into a single neutron. In this case, each taste modality is registered by non-overlapping cells and fibres.

• What is the across-fibre model?

  It comprises 2 contrasting submodels. Neurons are transporting the signals to the brain are not specialised for individual taste modalities, but that different signals registered by various TRCs are transported via the same neutron.
  
  Sub-models
  

  • Each TRC contains the receptors for each of the five basic taste modalities
  • Each TRC registers one of the basic taste modalities, but the signals from TRCs detecting different taste modalities can be transported to the brain by the same neuron

• 1.3 Bitter receptors

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• To which family of receptors do the bitter receptors belong to?

  The TAS2R or T2Rs.

• What is the T2R family?

  It contains about 25 different members.

• Why is there a large number of different bitter receptors?

  They have a role as early-warning system. Potentially toxic substances have large variety in chemical structure, which requires multiple sensors for detection.