Phosphate
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[edit] Chemistry
A phosphate group, or HPO32- is an inorganic molecule that plays several important roles in biochemistry. Because the molecule contains no carbon, the free form of the molecule is often referred to as inorganic phosphate, abbreviated as Pi.
Inorganic phosphate is the dissociated form of phosphoric acid, H3PO4.
[edit] Roles in biology
Phosphate groups combines with many other molecules to carry out important functions for life. Some of the more important roles are described below.
[edit] Nucleotides
Phosphate groups linked to nucleosides form the important class of molecules known as nucleotides. Nucleotides are formed by a combination of a sugar, a nitrogenous base and at least one phosphate group.
Some nucleotides, like adenosine triphosphate (ATP) and guanosine triphosphate (GTP) are used to store and transport energy in cells. Hydrolysis of these molecules removes the terminal phosphate group, leaving behind ADP or GDP and releasing energy that can be coupled by enzymes to energetically unfavorable processes. Energy released by respiration can be used to replenish supplies of ATP and GTP.
Nucleotides like cyclic AMP may also be used as intracellular messengers.
As their name suggests, nucleotides are also the basic building blocks of nucleic acids. The phosphate and sugar groups of nucleotides are linked to one another by phosphodiester bonds to form a chain of nucleotides into which information may be encoded. The information of our genome is encoded in the ordering of the sequence of AMP, GMP, TMP, and CMP that makes up our DNA.
[edit] Phospholipids
Phosphate groups are used to connect the hydrophobic tails of phospholipid molecules to the hydrophilic heads. Phospholipids are the main constituents of the phospholipid bilayer that makes up the plasma membrane of all cells, and segregates the organelles from the cytosol in eukaryotes.
[edit] References
- Alberts, B; Johnson, A; Lewis, J; Raff, M; Roberts, K; Walter, P. Molecular Biology of the Cell Third Edition, Garland Science 2002
- Lodish, H; Berk, A; Zipursky, S L; Matsudaira, P; Baltimore, D; Darnell, J E. Molecular cell Biology Fourth Edition, W.H. Freeman and Company 2000
