The Immune System and Antibiotics Quiz

This quiz covers the following specification points for Edexcel:
5.3, 5.12, 5.13, 5.14, 5.16 and 5.20

5.3.  Explain why the presence of one disease can lead to a higher susceptibility to other diseases:

There are three main reasons why this can be the case:

If you have a disease, your immune system is weakened and already occupied trying to fight off a pathogen. This means another pathogen could take advantage of this situation and spread within the body.

Diseases damage the natural defences – physical and chemical barriers (See point 5.12).

Disease stop organs from working effectively, which makes gaining a new disease more likely. For example, if your lungs are not working properly you will have less oxygen and more carbon dioxide in the body, leading to less energy through respiration, which could prevent other organs from properly functioning.

5.12 Describe how the physical barriers and chemical defences of the human body provide protection from pathogens, including:

Physical barriers, including mucus, cilia and skin

Chemical defence, including lysozymes and hydrochloric acid

Physical barriers prevent pathogens from entering the body and chemical barriers attempt to kill the pathogen before it can take hold in your body and cause disease.

5.13 Explain the role of the specific immune system of the human body in defence against disease, including:

Exposure to pathogens, the antigens trigger an immune response which causes the production of antibodies, the antigens also trigger the production of memory lymphocytes, the role of memory lymphocytes in the secondary response to the antigen.

As a reminder, pathogens are microorganisms that enter the body and cause disease, they are either: bacteria, fungi, protists or viruses.
Pathogens all have particular molecules on their surfaces that are unique to that pathogen. These molecules are called antigens.

Antibodies are one of the immune system’s weapons against pathogens. They are complementary molecules (opposite shapes to antigens) on the surfaces of white blood cells called lymphocytes.

These antibodies attach themselves to antigens and the antibodies are said to be activated. Activated lymphocytes divide over and over to produce clones.

Some lymphocytes secrete antibodies in large amounts and these stick to the antigens and destroy the pathogens or mark them for destruction by other types of white blood cells.

Other lymphocytes stay in the blood and are prepared to quickly attack the pathogen in the future if it returns, these are called memory lymphocytes. If the pathogen returns, we have a secondary response that is much faster and more effective at defending the body

5.14 Explain the body’s response to immunisation using an inactive form of a pathogen

The system described above with the secondary response is used during the process of immunisation, or vaccination.

We inject our bodies with weakened or dead pathogens and trigger the production of antibodies that can protect us if we ever encounter the pathogen again.

5.16 Explain that antibiotics can only be used to treat bacterial infections because they inhibit cell processes in the bacterium but not the host organism.

Antibiotics do not affect viruses, protists or fungi.

5.20 Describe that the process of developing new medicines, including antibiotics, has many stages, including discovery, development, preclinical and clinical testing.

• Pre-clinical – this is where we test a new drug on cells or tissues in the lab to see if they have the effect we want. If they do, animal testing is common to see how the effects on cells translate to the whole body and also to detect any dangerous side effects.
• Clinical – this begins with a small clinical trial on healthy people to test the safety and side effects, followed by larger clinical trials with people with the disease to determine an appropriate dose (how much of the drug is given to patients).