The amino acids in proteins are used in the body to build muscles and organs, transport molecules (hemoglobin), antibodies, and the organic catalysts known as enzymes. These are all critical molecules, and as such it is important to have a steady supply of amino acids, hence the pleasurable response to their presence in the mouth. Pungency (piquancy or hotness) had traditionally been considered a sixth basic taste. In 2015, researchers suggested a new basic taste of fatty acids called fat taste, although oleogustus and pinguis have both been proposed as alternate terms. Sweetness
Sweetness, usually regarded as a pleasurable sensation, is produced by the presence of sugars and substances that mimic sugar. Sweetness may be connected to aldehydes and ketones, which contain a carbonyl group. Sweetness is detected by a variety of G protein coupled receptors (GPCR) coupled to the G protein gustducin found on the taste buds. At least two different variants of the "sweetness receptors" must be activated for the brain to register sweetness. Compounds the brain senses as sweet are compounds that can bind with varying bond strength to two different sweetness receptors. These receptors are T1R2+3 (heterodimer) and T1R3 (homodimer), which account for all sweet sensing in humans and animals.Taste detection thresholds for sweet substances are rated relative to sucrose, which has an index of 1. The average human detection threshold for sucrose is 10 millimoles per liter. For lactose it is 30 millimoles per liter, with a sweetness index of 0.3, and 5-nitro-2-propoxyaniline 0.002 millimoles per liter.
Cause
Pertussis is caused by the bacterium Bordetella pertussis. It is an airborne disease (through droplets) that spreads easily through the coughs and sneezes of an infected person. Spread from animals
Uncertainties have existed of B. pertussis and whooping cough as a zoonotic disease since around 1910, but in the 1930s knowledge was gained that the bacteria lost their virulent power when repeatedly spread on agar media. This explained the difficulties to reproduce results from different studies as the pre-inoculating handlings of the bacteria were not standardized among scientists.Today it is established that at least some primate species are highly susceptible to B. pertussis and develop clinical whooping cough in high incidence when exposed to low inoculation doses. The bacteria may be present in wild animal populations, but this is not confirmed by laboratory diagnosis, although whooping cough is known among wild gorillas. Several zoos also have a long-standing custom of vaccinating their primates against whooping cough. Mechanism
After the bacteria are inhaled, they initially adhere to the ciliated epithelium in the nasopharynx. Surface proteins of B. pertussis, including filamentous hemaglutinin and pertactin, mediate attachment to the epithelium. The bacteria then multiply. In infants, who experience more severe disease, the bacteria spread down to the lungs.The bacteria secretes a number of toxins. Tracheal cytotoxin, a fragment of peptidoglycan, kills ciliated epithelial cells and thereby inhibits the mucociliary elevator by which mucus and debris are removed. TCT may contribute to the cough characteristic of pertussis. The cough may also be caused by a yet-to-be identified "cough toxin".