VIRUS
Definition:
Viruses are ultra-microscopic, non-cellular living particles, composed solely of a nucleic acid (DNA or RNA) core, surrounded by a protein envelope called capsid.
Characteristics of Viruses:
The major distinguishing characteristics of viruses are given below.
- They are non-cellular and very simple in structure, consisting mainly of a nucleic acid surrounded by a protein envelope called capsid. Therefore, a unit of virus is referred to as ‘a virus particle’ rather than ‘a virus cell’.
- They are devoid of the sophisticated enzymatic and biosynthetic machinery essential for independent activities of cellular life. Therefore, they can grow only inside suitable living cells. That is why; they are cultivated in the laboratory only inside living cells, unlike bacteria and fungi, which can be cultivated in the laboratory on non-living matter like nutrient agar.
- They are ultra-microscopic and can only be visualized under electron microscope.
- They do not increase in size.
- They can pass through filters, through which bacteria cannot pass.
- A virus is called either ‘DNA virus’ or ‘RNA virus’ depending on whether it contains the nucleic acid DNA or RNA. A virus cannot have both DNA and RNA
Viral Infection- consists of the following stages-
- Adsorption
- Penetration(Infection)
- Replication
- Maturation
- Release
How does washing with soap help get rid of the coronavirus?
Viruses such as coronavirus, influenza-causing viruses, Ebola, Zika have their genetic material encased in a layer of fat called the lipid envelop. Soap molecules are pin-shaped with a head that is water-loving (hydrophilic) and a tail that is oil-loving (oleophilic). Being oleophilic, the tail portion of the molecule tends to have an affinity for and ‘competes’ with the lipids in the virus envelope. Since the chemical bonds holding the virus together are not very strong, the long oleophilic tail gets inserted into the envelope and tends to have a ‘crowbar’ effect that breaks the lipid envelope of the virus. The tail also competes with the bond that binds the RNA and the lipid envelop thus dissolving the virus into its components which are then removed by water.
Do all viruses have the lipid layer?
No, certain viruses do not have the lipid envelop and are called the non-enveloped viruses. Rotavirus which causes severe diarrhoea, poliovirus, adenovirus that cause pneumonia and even human papillomavirus (HPV) do not contain the lipid envelop.
How do alcohol-based hand sanitisers help get rid of coronavirus?
Like soap, the alcohol present in hand sanitisers dissolve the lipid envelop, thus inactivating the virus. In addition, the alcohol also tends to change the shape or denature the mushroom-shaped protein structures that stick out of the lipid envelop. The mushroom-shaped protein structures help the virus to bind to special structures found on human cells and enter the cells. To be effective, the sanitisers should contain at least 60% alcohol.
Unlike soap lather, the alcohol does not come in contact with all parts of the hand. So care needs to be taken to use sufficient amount of sanitiser to increase the coverage. Unlike water, alcohol run does not remove the dead viruses from the hand. While a sanitiser can quickly reduce the number of microbes, it does not get rid of all types of germs, and is “not as effective when hands are visibly dirty or greasy”.
