Geranyl pyrophosphate (GPP, also called geranyl diphosphate) is a C10 isoprenoid made by joining two five-carbon isoprene units. In the trichome it sits at a fork: terpene synthases turn GPP into monoterpenes such as myrcene, limonene and pinene, while an aromatic prenyltransferase attaches its geranyl group to olivetolic acid to form CBGA. One more isoprene unit turns GPP into farnesyl pyrophosphate (FPP, C15), the start of the sesquiterpenes.
In practice
GPP links cannabinoid and terpene chemistry. Both compete for the same precursor supply in the same glands, which is one reason heavy-resin plants tend to be both potent and aromatic: they simply have more gland capacity. Whether pushing one pathway costs the other in a living plant is not well established. Growers never measure GPP; it is a concept for understanding the pathway.
Don't confuse with
- Geraniol: a monoterpene alcohol made from GPP, which can be measured on a terpene panel.
- Farnesyl pyrophosphate: the C15 precursor of sesquiterpenes.
- Pyrophosphate in fertilisers: unrelated.
A hair-like outgrowth of the plant's skin; in cannabis the glandular types make and store the resin holding cannabinoids and terpenes.Terpenes are volatile hydrocarbon compounds built from five-carbon isoprene units; in cannabis they are made in the trichome heads and are a major part of aroma and flavour.A monoterpene is a ten-carbon terpene made from geranyl pyrophosphate, such as myrcene, limonene, pinene or terpinolene; they are the most volatile terpenes and the first lost in drying.Olivetolic acid is the phenolic building block of cannabinoids; joined to geranyl pyrophosphate it forms CBGA, and its five-carbon chain becomes the pentyl tail of THC and CBD.CBGA (cannabigerolic acid) is the precursor cannabinoid that the plant converts into THCA, CBDA or CBCA, formed by joining olivetolic acid to geranyl pyrophosphate.A sesquiterpene is a fifteen-carbon terpene made from farnesyl pyrophosphate, such as beta-caryophyllene, humulene and bisabolol; they are heavier and less volatile than monoterpenes.A cannabinoid is any compound that binds the body's cannabinoid receptors or shares the typical cannabis terpenophenolic structure; the plant-made ones are phytocannabinoids such as THCA and CBDA.A terpene test measures the individual terpenes and total terpene content of a sample, usually by GC-FID or GC-MS, reported in % w/w or mg/g.A terpenoid is a terpene-derived compound that carries extra functional groups, usually oxygen (alcohols, oxides, ketones), such as linalool, bisabolol or caryophyllene oxide.
