Nitric Oxide

The elements of nitrogen and oxygen exist as alkaline earth metals, though they are not metals. The element nitrogen reacts with oxygen to give out several oxide molecules. Of all those oxides, one of the notable compounds is nitric oxide. It possesses two atoms, one nitrogen and one oxygen. Since the valency of nitrogen is not satisfied, the nitric oxide molecule contains free electrons that generally react with other high-affinity compounds. The compound is not involved to react with cellular amines, but it does function in the human body cells. Nitric oxide can lose or gain an oxygen atom quickly. Thus, it is highly susceptible to both oxidation and reduction.

Nitrogen 

Nitrogen is one of the non-metal elements in the periodic table. It has significant properties related to the reactions to form nitric oxide.

• The atomic number(Z) of a Nitrogen atom is 7, as it has 7 electrons and protons. 
• Its mass number(A) is 14, as it is the sum of the total protons and neutrons present in the nucleus of nitrogen. 
• It has a valency of 3 as only 5 electrons fill its outermost orbital instead of 8. 
• Thus, nitrogen reacts with species that contribute three electrons to the atom to attain a stable orbital. 

Oxygen 

Oxygen is a gas going along with the alkaline earth metals in the table. It shows the following properties when considering the reaction with nitrogen to form different oxides, especially nitric oxide.

• The atomic number(Z) is 8, as it possesses 8 electrons and protons.
• The mass number(A) is 16, which is the total number of protons and neutrons present in the nucleus of the oxygen atom. 
• Since it has a deficiency of two electrons in its outermost orbit, the valency of oxygen is 2.
• To attain a stable configuration, oxygen reacts with atoms or molecules that contribute two electrons. 

Monoxide of Nitrogen 

Nitric oxide is nothing but a nitrogen monoxide molecule. Its molecular formula is ‘NO’. It has one nitrogen and one oxygen bound together by an interaction called covalent bonding, which is formed by mutually contributing or sharing the electrons within the atomic species.

Physical Characteristics

The nitric oxide molecule has unique physical properties like the ones mentioned below.

• It exists in a gaseous phase of matter at room temperature and is colourless.
• The air of nitric oxide does not have any taste. 
• It generally has a higher mass than the normal atmospheric air.
• They do not burn efficiently. They are not flame-sensitive molecules. 
• In the liquid and solid phase, nitric oxide is blue in the shade.

Chemical Characteristics

The chemical characteristics of nitric oxide are as follows.

• Since the valency of nitrogen is not satisfied by the oxygen species, nitric acid has unpaired free electrons.
• Thus, the free radicals react with other molecules to occupy an orbital for better stability.
• It can lose an electron or two or can gain an electron or two to attain stability. 
• Thus, it is susceptible to both oxidation and reduction, resulting in NO+ or NO-formation.
• Since the molecule is a bit unstable, it is highly reactive with oxygen species, forming different nitrogen oxides like nitrogen oxides.

Significance 

The significance of nitric oxide is as follows – 

Cell protein modification 

• Nitric oxide is responsible for the nitrosation of sulfhydryl groups, which are also called ‘thiol’ groups, in a protein when it is synthesised in the human body. 
• It is called a post-translational modification.
• It is vital to human beings as it prepares the naive protein produced within us by our DNA for functioning and metabolising. 

Cell signalling and communication 

• Nitric oxide is essentially known for its activity in a crucial biological function in every bioform: cell communication.
• It is a mechanism by which the cell mass in bioform talks with each other to regulate their metabolism and prevention from dangers.
• They seem essential in regulating a bioform’s birth, growth, and development.

Air pollutants

• Nitric oxide forms when the hydrocarbon fuel sources burn in the presence of atmospheric air, running a combo of the atmospheric nitrogen with the oxygen atom at a high temperature.
• Such pollutants as nitric oxide, forming a mixture with atmospheric water vapour, results in a new product called nitric acid. 
• Nitric acid is a constituent of acid rain.

Homeostasis 

• Nitric oxide is generally manufactured by the cells of various organs.
• It is greatly responsible for maintaining the blood pressure of a person as it involves widening the vessels for blood flow.
• Nerve cells use it to transmit neuro signals for commanding our actions and metabolisms.
• The cells in our body responsible for our immunity also produce nitric oxide.
• These cells use nitric oxide as a poison to kill the pathogenic microorganism entering our body by disturbing and interfering with their metabolic activities.

Conclusion

The oxidation of the nitrogen atom yields a colourless gas, nitric oxide. It is blue when it is in the solid or liquid phase. In a Nitric oxide molecule, the valency of nitrogen is not satisfied by the oxygen molecule, so it is not much stable in its molecular form. Thus, it quickly reacts with other oxygen species to form a more stable nitrogen dioxide. They are susceptible to both oxidation and reduction easily. Nitric oxide does not react with cellular amines, but it reacts with thiols through the nitrosation of sulfhydryl as a post-translational modification.