As defined by the U.S. Geological Survey (USGS), heavy oil is a type of crude oil characterized by an asphaltic, dense, viscous nature (similar to molasses), and its asphaltene (very large molecules incorporating roughly 90 percent of the sulfur and metals ...

Cells, the basic unit of life, are surrounded by a limiting membrane called the plasma membrane. Inside cells, there are various membrane-bounded organelles, each of which has various and distinctive functions. How these organelles, which individually ...