Stroma

Stroma may refer to:

Biology

Stroma, Scotland

Stroma is an island off the northern coast of the mainland of Scotland. It is the most southerly of the islands in the Pentland Firth between the Orkney islands and Caithness, the northeasternmost part of the mainland. The name is from the Old Norse Straumr-øy meaning "island in the [tidal] stream".

The island's population fell from 375 people in 1901 to just 12 by 1961. The last native islanders left at the end of the following year, while Stroma's final abandonment came in 1997 when the lighthouse keepers and their families departed. Ancient stone structures testify to the presence of Stroma's earliest residents, while a Norse presence around 900–1,000 years ago is recorded in the Orkneyinga Saga. It has been politically united with Caithness since at least the 15th century. Although Stroma lies only a few miles off the Scottish coast, the savage weather and ferociously strong tides of the Pentland Firth meant that the island's inhabitants were very isolated, causing them to be largely self-sufficient, trading agricultural produce and fish with the mainlanders.

Stroma (fluid)

Stroma, in botany, refers to the colorless fluid surrounding the grana within the chloroplast.

Within the stroma are grana, stacks of thylakoids, the sub-organelles, the daughter cells, where photosynthesis is commenced before the chemical changes are completed in the stroma.

Photosynthesis occurs in two stages. In the first stage, light-dependent reactions capture the energy of light and use it to make the energy-storage molecules ATP and NADPH. During the second stage, the light-independent reactions use these products to capture and reduce carbon dioxide.

The series of biochemical redox reactions which take place in the stroma are collectively called the Calvin cycle or light-independent reactions. There are three phases: carbon fixation, reduction reactions, and ribulose 1,5-bisphosphate (RuBP) regeneration.

The stroma is also the location of chloroplast DNA and chloroplast ribosomes, and thus also the location of molecular processes including chloroplast DNA replication, and transcription/translation of some chloroplast proteins.