Cell wall The primary cell wall of land plants is composed of the polysaccharides cellulose, hemicelluloses and pectin. Often, other polymers such as lignin, suberin or cutin are anchored to or embedded in plant cell walls. Algae possess cell walls made of glycoproteins and polysaccharides such as carrageenan and agar that are absent from land plants. In bacteria, the cell wall is composed of peptidoglycan. The cell walls of archaea have various compositions, and may be formed of glycoprotein S-layers, pseudopeptidoglycan, or polysaccharides. Fungi possess cell walls made of the N-acetylglucosamine polymer chitin. Unusually, diatoms have a cell wall composed of biogenic
History of the petroleum industry Arabia due to its crude reserves derived from bitumen. History of the petroleum industry The petroleum industry is not of recent origin, but petroleum's current status as the key component of politics, society, and technology has its roots in the early 20th century. The invention of the internal combustion engine was the major influence in the rise in the importance of petroleum. According to Herodotus, more than four thousand years ago natural asphalt was employed in the construction of the walls and towers of Babylon, great quantities of it were found on the banks of the river Issus, one of