Receptor molecules are found on the top of microvilli of the taste cells. SweetnessSweetness is produced by the presence of sugars, some proteins, and other substances such as alcohols like anethol, glycerol and propylene glycol, saponins such as glycyrrhizin, artificial sweeteners (organic compounds with a variety of structures), and lead compounds such as lead acetate. It is often connected to aldehydes and ketones, which contain a carbonyl group. Many foods can be perceived as sweet regardless of their actual sugar content. For example, some plants such as liquorice, anise or stevia can be used as sweeteners. Rebaudioside A is a steviol glycoside coming from stevia that is 200 times sweeter than sugar. Lead acetate and other lead compounds were used as sweeteners, mostly for wine, until lead poisoning became known. Romans used to deliberately boil the must inside of lead vessels to make a sweeter wine. Sweetness is detected by a variety of G protein-coupled receptors coupled to a G protein that acts as an intermediary in the communication between taste bud and brain, gustducin. These receptors are T1R2+3 (heterodimer) and T1R3 (homodimer), which account for sweet sensing in humans and other animals.
In some types of ED, abnormal development of parts of the eye can result in dryness of the eye, cataracts, and vision defects. Professional eye care can help minimize the effects of ED on vision. Similarly, abnormalities in the development of the ear may cause hearing problems. Respiratory infections can be more common because the normal protective secretions of the mouth and nose are not present. Precautions must be taken to limit infections. Genetics
ED can be classified by inheritance (autosomal dominant, autosomal recessive and X-linked) or by which structures are involved (hair, teeth, nails and/or sweat glands). There are several different types with distinct genetic causes:

Hay–Wells syndrome (Rapp–Hodgkin syndrome) and EEC syndrome are all associated with TP63. Hypohidrotic ectodermal dysplasia can be associated with EDA, EDAR and EDARADD. Margarita Island ectodermal dysplasia is associated with PVRL1. Ectodermal dysplasia with skin fragility is associated with PKP1. Cloustons hidrotic ectodermal dysplasia is associated with GJB6. Naegeli syndrome/Dermatopathia pigmentosa reticulariss is associated with KRT14. Pachyonychia congenita is caused by multiple keratins. Focal dermal hypoplasia is associated with PORCN. Ellis–van Creveld syndrome is associated with EVC. Palmoplantar ectodermal dysplasia refers to several different conditions selectively affecting the hands and feet.