Functional groups are the parts of molecules involved in chemical reactions
The distinctive properties of an organic molecule depend not only on the arrangement of its carbon skeleton, but also on the molecular components attached to that skeleton.
The Functional Groups Most Important in the Chemistry of Life
The components of organic molecules that are most commonly involved in chemical reactions are known as functional groups. If we think of hydrocarbons as the simplest organic molecules, we can view functional groups as attachments that replace one or more of the hydrogens bonded to the carbon skeleton of the hydrocarbon.
The six functional groups most important in the chemistry of life are the hydroxyl, carbonyl, carboxyl, amino, sulfhydryl, and phosphate groups. These groups are hydrophilic and thus increase the solubility of organic compounds in water.
ATP: An Important Source of Energy for Cellular Processes
Adenosine triphosphate , or ATP, is the primary energy–transferring molecule in a cell. ATP consists of an organic molecule called adenosine attached to a string of three phosphate groups:
Where three phosphates are present in series, as in ATP, one phosphate may split off as an inorganic phosphate ion (HOPO32-). Losing one phosphate, ATP becomes adenosine diphosphate, or ADP. The reaction releases energy that can be used by the cells.
Review Questions
1. What change usually occurs in ATP when it releases energy?
Answer: The ATP molecule loses a phosphate, becoming ADP.