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LEARNING TARGETS
LEARNING TARGETS
Outline the lines of defence against pathogens available to humans
Distinguish between specific and unspecific response
Describe the different types of white blood cells and outline their roles
Describe the process of making antibodies using proper terminology
Read " A Bug's life" and be able to answer questions regarding pathogens
Use this document to learn new terms
Use this document to learn new terms
Lines of defence
Lines of defence
When microorganisms enter the body, they release toxins. The toxins damage cells to cause the symptoms of the disease. The body’s first line of defence is its natural barriers which include:
skin
chemicals in tears
chemicals in sweat
stomach acid.
White blood cells
White blood cells
The body’s first line of defence is preventing the pathogen from entering in the first place. If a pathogen manages to get into the body, the second line of defence takes over and the white blood cells have key functions in this.
Functions of the white blood cells
Functions of the white blood cells
White blood cells can:
Engulf pathogens and digest them
produce antibodies to destroy pathogens
produce antitoxins that neutralise the toxins released by pathogens.
In a written examination, it is easy to get carried away with metaphors about invaders and battles: stick to the point. Note that:
the pathogens are not the disease, they cause the disease.
white blood cells do not eat the pathogens, they ingest them.
antibodies and antitoxins are not living things, they are specialised proteins.
Types of white blood cell
Types of white blood cell
There are several types of white blood cell [cells which fight disease by making antibodies or engulfing germs ], each with a different function. But there are two main groups. The first of these are Phagocytes which engulf and digest bacteria (a process called Phagocytosis).
These cells can pass easily through blood vessel walls into the surrounding tissue, and move towards pathogens [microorganisms that cause disease]
A white blood cell ingesting disease-causing bacteria.
The second type of white blood cells are called Lymphocytes and they produces antibodies to label microorganisms. Pathogens contain certain chemicals that are foreign to the body. These are called antigens [Foreign organisms that get into the body, and trigger an immune response. ]. Each of this group of white blood cell carries a specific type of antibody - a protein with a chemical ‘fit’ to a certain antigen. When a white blood cell with the appropriate antibody meets the antigen, the white blood cell reproduces quickly to make many copies of the antibody that neutralizes the pathogen.
The second type of white blood cells are called Lymphocytes and they produces antibodies to label microorganisms. Pathogens contain certain chemicals that are foreign to the body. These are called antigens [Foreign organisms that get into the body, and trigger an immune response. ]. Each of this group of white blood cell carries a specific type of antibody - a protein with a chemical ‘fit’ to a certain antigen. When a white blood cell with the appropriate antibody meets the antigen, the white blood cell reproduces quickly to make many copies of the antibody that neutralizes the pathogen.
Memory cells
Memory cells
Memory cells are a type of white blood cell that can respond quickly when it meets a microorganism for the second time. They produce the right antibody for the particular microorganism and destroy it before you feel unwell. This is described as being immune to a disease.
Mutation rate
Mutation rate
On average an adult human will catch two to four colds every year, and a child will catch even more (because their immune system is still developing. This happens for two main reasons:
there are hundreds of different cold viruses
the viruses have a high mutation rate
A high mutation rate means that the DNA of the virus frequently changes, so the human body has to destroy the virus using a different antibody each time, which makes it harder to develop immunity.
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