There are three main types of cellular work: chemical, transport, and movement. Most of this work is powered by the transfer of a phosphate group from one molecule to another in a process known as . 2. Through energy coupling, cells use , or energy-releasing, reactions to drive , or energy-requiring, reactions. The molecule is the energy shuttle between these two types of reactions. 3. A specific speeds up each of a cell's chemical reactions. 4. Mechanisms such as enable precise control over a cell's -- all of its chemical reactions.