A cell's daily operations are accomplished through the biochemical reactions that take place within the cell. Reactions are turned on and off or sped up and slowed down according to the cell's ...

Interphase The cell spends most of its life in this phase. The DNA in chromosomes copies itself ready for mitosis. Prophase The DNA in chromosomes and their copies condenses to become more visible.

A solar cell is made of two types of semiconductors, called p-type and n-type silicon. The p-type silicon is produced by adding atoms—such as boron or gallium—that have one less electron in their ...