7.Bitter and sweet substances do not ionize. Sweetness likely is related to sugar content. Bitterness may be related to many poisons, and deters us. It often has strong motivational effects. Rotten-meat smell is an emetic.
Some scents attract.
Menstrual cycles can be influenced by smell. Olfaction's receptors have cilia in the olfactory mucosa, 5cm square surfaces, in the nasal passages. The cilia are excited by chemical interactions with an odour's molecules. This controls many aspects of motivation and emotion. Then signals go to the frontal cortex.