1 Pepsin is the main gastric enzyme. 2  It is produced by the stomach cells called chief cells in its inactive form pepsinogen, which is a zymogen. 3  Pepsinogen is then activated by the stomach acid into its active form, pepsin.
Single (music) In music, a single, record single or music single is a type of release, typically a song recording of fewer tracks than an LP record, an album or an EP record. This can be released for sale to the public in a variety of different formats. In most cases, a single is a song that is released separately from an album, although it usually also appears on an album. Typically, these are the songs from albums that are released separately for promotional uses such as digital download or commercial radio
Presently, an American RIAA-certified Gold record is a single or album that has sold 500,000 units (records, tapes or compact discs). The award was launched in 1958; originally, the requirement for a Gold single was one million units sold and a Gold album represented $1 million in sales (at wholesale value, around a third of the list price). In 1975, the additional requirement of 500,000 units sold was added for Gold albums. Reflecting growth in record sales, the Platinum award was added in 1976 for albums selling one million units, and singles selling two million units.