Short answers, pulled from the story.
The fifth taste umami was discovered in 1907 by the Japanese chemist Kikunae Ikeda. He isolated the savory taste from the broth of seaweed and named it umami. This discovery shattered the Western scientific consensus that there were only four basic tastes.
The five basic tastes are sweet, sour, salty, bitter, and umami. Sweetness signals carbohydrates for energy, sourness indicates acidity, saltiness maintains ion homeostasis, bitterness warns of poisons, and umami detects amino acids for building muscles and organs.
Supertasters are individuals with an increased number of fungiform papillae on their tongues that experience heightened taste sensitivity. Their genetic variation at the TAS2R38 locus determines their ability to taste bitter substances like phenylthiocarbamide and 6-n-propylthiouracil. This genetic basis makes them require less fat and sugar while consuming more salt than others.
Taste involves specific molecules binding to receptors on taste buds to detect sweet, sour, salty, bitter, and umami flavors. Chemesthetic responses like heat and cold involve the trigeminal nerve and substances such as capsaicin or menthol. These sensations are not tastes but complex interactions between the nervous system and chemical properties of food.
Cats cannot taste sweetness while several carnivores like hyenas, dolphins, and sea lions have lost the ability to sense up to four of their ancestral five basic tastes. This loss of function resulted from changes in diet and environment that allowed these species to adapt to their specific ecological niches.