Summary
Thank you to EPAM for sponsoring the development of this activity. EPAM is a leading global provider of software product development and digital platform engineering services to hundreds of Fortune 500 and 1000 clients located around the world. EPAM’s corporate social responsibility goals are driven by their values, correspond with the United Nation’s Sustainable Development Goals, and are guided by ISO 26000 standards, which provide guidance on how businesses can operate in a socially responsible way. EPAM is committed to serving as an ethical organization and sharing their time and talent to improve tech education around the world, contributing to the sustainability of their local communities.
Introduction
Have you ever wondered why we wash our hands with water and soap to get rid of bacteria and viruses? Good hand hygiene becomes especially important during viral outbreaks such as the COVID-19 pandemic! The CDC (Center for Disease Control) recommendations for handwashing say to scrub your hands for at least 20 seconds with water and soap. But how does soap kill viruses such as SARS-COV-2? In this activity, you will find out by experimenting with models of different virus types to see how they react to soap.
Materials
- Aluminum foil
- Double-sided tape that stays sticky when wet
- Butter
- Butter knife
- Small plate
- Sprinkles (the waxy elongated kind) or cracked pepper
- Bowl
- Warm water
- Paper towel
- Soap
- Spoon
Prep Work
- Check to make sure the type of sprinkles you are using do not dissolve in warm water. Pour a few in a small bowl of warm water and wait two or three minutes. If they do dissolve, use cracked pepper instead of the sprinkles.
- Refill the bowl with warm water and add two squirts of hand soap.
- Mix the soapy water with a spoon until all the soap has dissolved.
- Pour a heap of sprinkles onto a small plate.
- Keep this diagram of the two types of viruses handy to look at as you build your virus models. If you prefer, download and print a PDF of the virus diagram.
Both non-enveloped and enveloped viruses have genetic material (RNA or DNA), surrounded by a protein shell called a Capsid. In non-enveloped viruses the proteins that attach to receptors on a host cell are found on the outside of the Capsid. In contrast, in enveloped viruses a lipid membrane envelope surrounds the Capsid and the attachment proteins are embedded in the lipid membrane envelope.
Instructions
- First, you will make your virus models.
- Roll two balls out of the aluminum foil that have a ½-inch diameter each.
What do you think the aluminum ball represents in your virus model? Hint: Look at the virus diagram, what is at the center?
- Cover each of the aluminum balls with double-sided tape.
What do you think the double-sided tape mimics in your virus model?
- Roll one aluminum ball around in the sprinkles.
What do the sprinkles represent in your virus model?
- Cover the second aluminum ball in butter from all sides. It should have an even layer of butter around it.
Looking at the virus diagram, what does the butter mimic in your virus model?
- Roll the aluminum ball with the butter around in the sprinkles.
- Place both of your virus models next to each other.
How do they compare? How are they similar or different? Which model do you think represents the enveloped virus and which one represents the non-enveloped virus?
- Carefully drop both virus models into the bowl with the soapy water. Swirl the water with a spoon to make sure both virus models get splashed with water from all sides. Observe the virus models for at least 2 minutes.
What do you notice happening over time?
- After 2 minutes, take both aluminum balls out of the soapy water and place them next to each other on a paper towel.
Do they both look the same? If not, how do they look different? Can you explain your results?
- Think about what your results mean.
What do your results tell you about how real viruses get affected by washing your hands with soap and water?
Cleanup
What Happened?
As you might have guessed, you built two different virus models in this activity. One model represented a non-enveloped virus and the other model an enveloped virus like SARS-COV-2 (the coronavirus that causes COVID-19). They both have the same basic structure which was represented by the aluminum ball and the double-sided tape in your virus model. Here is what each part of the model represented:
- The aluminum foil represented the nucleic acid core which carries the viruses' genetic information in the form of RNA or DNA.
- The double-sided tape mimicked the protein shell or capsid with surrounds and protects the virus's RNA or DNA.
- The butter represented the lipid membrane that envelopes, or surrounds, the capsid of enveloped viruses. The fats in butter are a type of lipid similar to the lipids in virus envelops. This membrane does not exist in non-enveloped viruses which is why you only put butter on one of your models.
- The sprinkles in your model represented proteins that a virus uses to attach to the outside of its host cell. In a non-enveloped virus, they are located on the surface of the capsid, whereas they are on the surface of the lipid membrane envelope for an enveloped virus. If those proteins are damaged, lost, or destroyed, the virus particle can no longer infect its host.
Dropping both virus models into soapy water mimicked washing your hands with warm water and soap. Swirling the viruses around in the water is similar to you scrubbing your hands with soap. You should have noticed that the butter, which represents the lipid membrane envelope, slowly dissolved in the soapy warm water. This is because the soap molecules interact with the butter molecules, which leads to the butter layer being destroyed. As a result, the enveloped virus model should have lost all its sprinkles over time. The non-enveloped virus on the other hand should have kept its sprinkles for a much longer time, although eventually it might lose some of them, too. This means that using soap during hand washing can help make enveloped viruses, like the one that causes COVID-19, noninfectious. Which keeps all of us healthier!
You can read more about enveloped and non-enveloped viruses in the Digging Deeper section.
Digging Deeper
If you ever had a common cold or the flu, you had a viral infection! A virus is a type of germ that can cause diseases in people such as the cold, the flu (influenza), chicken pox or COVID-19. But how does a virus make a person sick? To make someone sick, a virus first has to infect a person, which means that it has to get inside a person's body. It often enters through the nose, mouth, or breaks in the skin. Once inside a person, or host, a virus attaches to the outer walls of the host's cells. When attached, the virus releases its genetic material (its DNA or RNA) into the cell and then hijacks its replication machinery to make more virus particles (Figure 1). The higher number of cells that get infected by the virus, the sicker a person gets.
Some types of viruses enter the human body through the nose, mouth, or breaks in skin. Once inside they go through six steps. First, the virus attaches to the host cell. Second, the virus gets inside the host cell. Third, the virus releases its RNA or DNA inside the host cell. Fourth, the newly assembled viruses get released from the host cell. Fifth, the new viruses get assembled inside the host cell. Sixth, new virus parts are made inside the host cell. Sixth, the newly assembled viruses get released from the host cell.
Figure 1. Diagram showing how a virus infects its host (left) and what happens inside an infected body (right).
So how can you protect yourself from being infected by a virus? Your first line of defense is to not allow a virus to enter your body to begin with. This means staying away from people who are or could be sick, avoiding touching your nose, mouth or face, and practicing good hand hygiene. The Center for Disease Control recommends scrubbing your hands for at least 20 seconds with water and soap to get rid of viruses such as SARS-COV-2. Why is hand washing so important and how does it affect the virus? The simple answer is that the mechanical action of hand washing dislodges and carries away most of the virus. But soap also plays an important part in killing some viruses.
Viruses come in many different shapes and sizes. All viruses consist of a nucleic acid core which includes their RNA or DNA, and an outer protein shell which is called the capsid. In addition to this basic structure, some viruses such as SARS-COV-2, the coronavirus that causes COVID-19, have an additional outer lipid membrane envelope that surrounds its capsid (Figure 2).
Both non-enveloped and enveloped viruses have genetic material (RNA or DNA), surrounded by a protein shell called a Capsid. In non-enveloped viruses the proteins that attach to receptors on a host cell are found on the outside of the Capsid. In contrast, in enveloped viruses a lipid membrane envelope surrounds the Capsid and the attachment proteins are embedded in the lipid membrane envelope.
Figure 2. Structures of a non-envelope virus (left) and an enveloped virus (right).
The attachment tools that a virus needs to hook onto the host cell are located on the outside surface of the virus. Many viruses use proteins to interact with its host cell. For non-enveloped viruses these proteins are located on the surface of the capsid whereas for an enveloped virus the attachment proteins are located on the surface of its lipid membrane envelope (Figure 2).
Enveloped viruses, such as SARS-COV-2, are much more susceptible to soap than non-enveloped viruses, like the viruses which cause polio and hepatitis A. This is because of their lipid membrane envelope. The lipid membrane is made of two layers of lipid molecules that have a hydrophilic (water loving) head and a hydrophobic (water hating) tail. Within this lipid bilayer the hydrophobic tails point toward the center of the sheet whereas the hydrophilic heads face to the outside (Figure 3).
Figure 3. Structure of a lipid bilayer formed by lipid molecules with a hydrophilic head and a hydrophobic tail.
Detergent or soap molecules have a very similar structure to the lipids in a lipid bilayer. They also have hydrophobic tail and a hydrophilic head but are usually assembled as a spherical structure (a micelle) in which the hydrophobic tails also point inward and the hydrophilic heads outward (Figure 4).
Figure 4. Structure of a detergent micelle.
When detergent micelles come into contact with a lipid bilayer, a process called solubilization happens. This means that the detergent disintegrates the lipid bilayer by incorporating its detergent molecules into the lipid bilayer and also pulling lipids from the bilayer into its detergent micelles (Figure 5). As a result, the lipid membrane dissolves, and the enveloped virus is left without its envelope. With its envelope, the virus also loses its host cell attachment machinery, which means that the virus cannot hook onto a host cell anymore. The soap has successfully inactivated the virus!
Lipid bilayer membranes are made up of two rows of lipid molecules oriented back-to-back. Detergent molecules disrupt the organization of the lipid membrane by pulling lipid molecules out of the rows and into a circle of detergent molecules called a micelle. Free floating detergent molecules then insert themselves into the lipid bilayer thus ruining the membrane structure.
Figure 5. Schematic drawing showing how detergents solubilize lipid bilayers.
Ask an Expert
For Further Exploration
- With a timer, measure how long it takes until all the sprinkles are gone from the enveloped virus model. Do you now know why a quick hand wash is not as effective as washing your hands for at least 20 seconds?
- Repeat the experiment, but this time use cold water and soap in your bowl. How do your results change?
- Find out what other shapes a virus can have! Research online or find a book about viruses and draw all virus shapes that you can find on a piece of paper. What are the viruses' names and what diseases do they cause?
Related Resources
Project Ideas
Activities
Links
- Lumen: Structure of Viruses
- Chagrin Valley Soap and Salve: How Does Soap Work?
- cK-12: Phospholipid bilayer
- Science Magazine: Does disinfecting surfaces really prevent the spread of coronavirus?
