The UK's most valuable monument is deemed to be the 1,000-year-old Tower of London, which is worth an estimated Â£56billion to the British economy and came it at number five in the list of European list. Its value is six times more than its nearest rival the Colosseum in Rome, which is valued at Â£72billion.
Cell cycle checkpoints are control mechanisms in eukaryotic cells which ensure proper division of the cell.
Mitochondria - the cell's 'power plants' - generate most of the cell's supply of the energy-carrying molecule adenosine triphosphate (ATP). MItochondria are also involved in a range of other processes: signalling, cellular differentiation, cell death, control of the cell cycle, and cell growth.