- Readings and Assignments
- Germs:
- Directions: Read the following information about germs, then answer the questions that follow.
Did You Know… Germs
Whether we like it or not, germs are a part of our lives. Although some germs are helpful, many can cause serious illnesses. Germs, or pathogens, are small organisms (living things) that can cause diseases; there are four major classes of germs: bacteria, viruses, fungi and protozoa.
Bacterial infections are caused by small, single-celled bacteria that can live on their own. These microscopic organisms live all throughout our environment including on your body and in your food. Ever heard of probiotic yogurt? This is yogurt that contains bacterial cultures that help regulate digestion. Even though some types of bacteria are helpful to humans, bacteria can also be harmful to humans. Infections like strep throat and tuberculosis are both caused by bacterial cells.
Viruses are even smaller than bacteria and cannot live on their own. If you look at the diagram of bacteria and viruses above, you can see that a virus lacks important cell structures such as a cell wall, cell membrane or ribosomes. For these reasons, viruses need to inside another living organism to reproduce, grow and survive. Although viruses cannot survive outside of a host for a long period of time, they sometimes survive long enough to meet an unsuspecting live host. Once viruses have entered your body, they can reproduce to cause infections such as the common cold and smallpox.
Fungal infections are caused by multi-celled organisms (plural fungi) that are sometimes mistaken as plants. Most fungi are not harmful to humans, such as the mushrooms in mushroom soup, but some fungi can cause infections such as athlete’s foot and ringworm. Protozoa are single-celled organisms, like bacteria, that like moist environments. Thus, protozoan infections are commonly spread through contaminated water. Malaria is an example of a disease caused by protozoa.
Information adapted on April 26, 2016 from http://kidshealth.org/en/teens/care-about-germs.html#cat20119
When one of the many germs gets into your body, illness can occur. Your immune system, which is made up of leukocytes (white blood cells), proteins, lymph nodes and lymphoid organs (spleen, thymus and tonsils), defends you against these invaders. Through a series of steps called an immune response, your immune system attacks germs to protect your body. There are two basic types of leukocytes:
- The phagocytes are cells that chew up invading organisms.
- The lymphocytes are cells that allow the body to remember and recognize previous invaders and help the body destroy them. There are two kinds of lymphocytes: B lymphocytes and T lymphocytes.
B lymphocytes are activated when an antigen (foreign substance) invades the body. B lymphocytes will then create antibodies, or specialized proteins that lock onto a specific antigen. Antibodies and antigens fit together like a lock and key. Thus, antibodies are specific to only one antigen. Once the B lymphocytes recognize specific antigens, they develop a memory for the antigen and will produce antibodies the next time the antigen enters your body. That's why if someone gets sick with a certain disease, like chickenpox, that person typically doesn't get sick from it again. This concept is also true when you get a vaccination. Although antibodies can recognize an antigen and lock onto it, they are not capable of destroying it without help. That is the job of the T lymphocytes. Together, your B and T cells work to rid your body of the invading germs. We cannot see your immune system at work, but we can see physical symptoms that tell us our immune system is working. For example, coughing, sneezing, fever, inflammation, vomiting, diarrhea, being tired and cramping can all indicate a bacterial or viral infection. Being that these germs can make a person quite ill, it is important to help prevent the spread of germs. 
The most effective way to prevent the infections that are caused by germs is by protecting yourself. Most germs are spread through the air by coughing or sneezing or through bodily fluids such as blood, saliva or semen. Thus, avoiding contact with these substances by washing your hands, using safe food handling procedures and cleaning surfaces thoroughly is the best way to prevent the spread of illness. Vaccinations are another way to protect yourself from harmful germs as these expose your B lymphocytes to the antigen in a less harmful way and your immune system will still be able to remember it the next time it encounters this germ.
Questions:
- What are the four classes of germs? How can these germs be harmful to the body?
- In one sentence, describe what the immune system does for your body?
- Once germs enter the body, what happens? Make a list of 5 symptoms that tell you your body is fighting them off.
- Think about when you might encounter germs. List two reasons when it is important to wash your hands.
- Washing hands is just one way to prevent germs from spreading. List three other ways you can help fight the battle against germs.
