Phosphates are important in many aspects. For one, phosphates allow us to have the energy to live another day through a molecule known as adenosine triphosphate (ATP). Our cells use this so we can have energy to keep our cells working, make our muscles contract, and so much more. We use phosphates not only in our bodies but also in the food we eat. Phosphates are well-known components of fertilizers.
Itโs important to have a basic foundation about phosphates and how they are used in our body because we use them in a lot of biological systems. In the MCAT, you might get tested on what you know about phosphorus-containing compoundsโspecifically on the role of phosphates in cellular functions.
I. Organic Vs. Inorganic Phosphates
In our article on phosphorus-containing compounds, we defined phosphates as a functional group characterized by a central phosphorus atom bonded to four oxygen atoms, with one bond being a double bond and the remaining three a single bond. We also defined it as a derivative of phosphoric acid.
Another definition to better understand phosphates is by thinking of it as a salt of phosphoric acid. It takes a form that all life can use. Weโll later tackle why we all seem to need phosphates in an article on their properties. However, for now, understand that the negative charge the three oxygen atoms contribute to the ion makes it highly participative in chemical processes.
A. Organic Phosphates
The simplest way we can define organic phosphates is by looking at their bonds. Organic phosphates are bound to carbon chains or any molecule that contains carbon. An excellent example of this is Adenosine triphosphate (ATP), the energy our cells use for various processes. Organic phosphates will always have complex structures, and most of them are responsible for energy transfer. They also form covalent bonds between atoms.
B. Inorganic Phosphates
Inorganic phosphates are basically anything that is not bonded to carbon. We see inorganic phosphates in minerals and salts, and they are always combined with cations due to their negative charge. They are primarily used for industrial purposes in agriculture and water treatment. There are three types of inorganic phosphates that might be helpful to know of.
- Orthophosphates - The most basic and used form of phosphates.
- Polyphosphates - A chain of phosphate ions.
- Pyrophosphates - A phosphate consisting of two phosphate groups.
- Metaphosphates - A phosphate that has a ring-like formation.
Key Differences
- Organic compounds have carbon, whereas inorganic compounds donโt.
- Organic compounds form covalent bonds, and inorganic compounds sometimes form ionic bonds.
- Organic compounds have a more complex structure due to the presence of carbon.
II. Phosphorylation
Phosphorylation is a process wherein phosphate is added to a molecule, such as a protein. For proteins in our body, phosphorylation allows the proteins to stabilize and modify themselves so they can provide their function.
One way phosphorylation might occur is through kinase-catalyzed protein phosphorylation. Here, a phosphate is added to an amino acid in a protein. Kinases transfer phosphates to specific proteins. Phosphates do not directly give energy to proteins, however, adding a phosphate group allows the protein to improve its role in biological processes.
Phosphorylase is an enzyme that catalyzes the addition of an inorganic phosphate to a molecule. In the breakdown of glycogen, glycogen phosphorylase acts as an enzyme to add an inorganic phase to the end of a glycogen chain, which breaks one unit of glucose from the chain, forming glucose-1-phosphate.
III. Conclusion
Phosphorus-containing compounds can be classified as organic or inorganic. Organic phosphates have a complex structure due to their bond with carbon. Inorganic phosphates, on the other hand, are not bonded to carbon and will often have a less complicated structure. Most organic compounds are essential in biological systems. In contrast, inorganic compounds are usually more well-known for their use in the agriculture industry. One vital process in our body is phosphorylation, wherein phosphorus is added to modify protein. Our cells need phosphates for energy management, protein function, sending signals, and other purposes, especially in our cells.
IV. Key Terms
- Enzyme - A chemical species that accelerates reactions without being consumed.
- Glucose - A simple sugar that serves as a primary source of energy for cells.
- Inorganic phosphate - A phosphate ion that is free in a solution.
- Kinase - An enzyme that catalyzes the transfer of phosphate to a molecule.
- Organic phosphate - A phosphate group that is covalently bonded to carbon-containing molecules.
- Phosphorylase - An enzyme that catalyzes the addition of inorganic phosphate to a molecule.
- Phosphate (PO43-) - A compound consisting of phosphorus bonded to four oxygen atoms, with one oxygen being double-bonded and the other three being single-bonded.
V. Practice Questions
Sample Practice Question 1
In an aqueous solution, pyrophosphate will likely:
A. degrade into phosphate
B. be unstable and inert.
C. degrade into inorganic phosphate
D. reduce the polarity of the solution
Ans. C
Sample Practice Question 2
Which of the following is false?
A. Phosphorylase catalyzes the addition of an inorganic phosphate to break down a glycogen chain.
B. Kinase catalyzes the addition of a phosphate to adenosine triphosphate (ATP).
C. Phosphoric acid can donate three protons to form a phosphate ion.
D. Phosphate helps in modifying protein.
Ans. B
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