Immunity Flashcards
What are pathogens
Organisms that cause diseases
What are parasites
Organisms which live on another living thing (the host) and cause harm to them
What’s an immune response
A response to an antigen which involves the activation of lymphocytes
What are antibodies
Protein molecules released by the immune system in response to an antigen, which are capable of neutralising the antigen
Describe the skin as a primary defence
Acts as a physical barrier blocking pathogens from entering the body. Also acts as a chemical barrier by producing chemicals that are antimicrobial and lower ph, inhibiting pathogen growth
Describe mucous membranes as a primary defence
Protect body openings that are exposed to the environment eg mouth genitals nostrils. Some membranes secrete mucus which is a sticky substance that traps pathogens and contains antimicrobial enzymes.
What are phagocytes
A type of white blood cell that carries out phagocytosis whuch is the engulfment of pathogens. Found in blood and issues and are the first cells to respond to a pathogen inside the body
How does a phagocyte respond to a pathogen
Recognises the antigens on the pathogens surface and the cytoplasm of the phagocyte surrounds it, englulfing it. Pathogen is now in jail which is technically called a phagocytic vacuole. A lysosomes fuses with the phagocytic vacuole and the enzymes released break down the pathogen. The phagocyte then presents the pathogens antigens on its surface to activate other immune system cells
How do t lymphocytes work in the immune response
Activated by phagocytes. Surface is covered with receptors whuch bind to antigen presented by phagocyte. Each t lymphocyte has a different receptor on its surface. When the receptor on the surface of a t lymphocyte meets a complimentary antigen it binds to it. This activates the t lymphocytes and this is called clonal selection. The t lymphocyte then undergoes clonal expansion which is where it divides to produce clones which then differentiate into different types of t lymphocytes which carry out different functions. Helper t cells activate b lymphocytes
What are b lymphocytes
Covered with antibodies that can bind to antigens to fork an antigen antibody complex. Each b lymphocyte has a different shaped antibody on its surface.
How do b lymphocytes work
Activated by helper t cells. When the antibody on the surface of a b lymphocyte meets a complimentarily shaped antigen it binds to it. This together with substances released from the helper t fells activats the b lymphocytes, and this is clonal selection. The activated b lymphocyte divide by mitosis into plasma cells and memory cells and this is called clonal expansion
What order does the immune response work in
Phagocytes. T lymphocytes. B lymphocytes.
Describe cell signalling and why it’s important in the immune response
It’s how cells communicate. A cell may release or present a substance that binds to the receptors on another cell which causes a response. Cell signalling is important in the immune response because it activates all the different types of white blood cells thy are needed, eg helper t cells release substances that activate b lymphocytes
What are plasma cells
Clones of the b lymphocyte. They secrete the antibody into the blood. These antibodies will bind to the antigens on the surface of the pathogen to for, antigen antibody complexes
Draw the structure of an antibody
Variable regions, light chain, heavy chain, hinge protein, disulphide bridge, constant region
Tell me about the structure of an antibody
The variable regions form the antigen binding site. The shape of the variable region is complimentary to a particular antigen. The variable regions differ between antibodies. The hinge region allows flexibility when the antibody binds to the antigen. The constant regions allow binding to receptors on immune system cells eg phagocytes and is the same in all antibodies. Disulphide bridges hold the polypeptide chains together
What are the three ways antibodies helpr to clear an infection
Agglutination pathogens. Neutralising toxins. Preventing the pathogen binding to human cells.
How do antibodies help to clear an infection by agglutinating pathogens
Each antibody has two binding sites so an antibody can bind to two pathogens at once - the pathogens become clumped together. Phagocytes then bind to the antibodies and phagocytose a lot of pathogens all at once
How do antibodies help to clear an infection by neutralising toxins
Antibodies can bind to the toxins produced by pathogens. This prevents the toxins from affecting human cells so the toxins are neutralised. The toxin-antibody complexes are phagocytosed.
How do antibodies help to clear an infection by preventing the pathogen binding to human cells
When antibodies bind to the antigens on pathogens they may block the cell surface receptors that the pathogen needs to bind to the host cells. This means the pathogen can’t attach to or infect the host cells.
Explain the differences between the primary and secondary immune responses
Primary is where pathogen enters first time. Secondary is second time. Primary is slow secondary is fast. Primary activates b and t lymphocytes and secondary activates memory cells pimary has symptoms and secondary doesn’t
What is the primary response
When a pathogen enters the body for the first time the antigens on its surface activate the immune system. This is called the primary response.
Describe the primary response
It’s slow because there aren’t many b lymphocytes at can make the antibody needed. Eventually the body will produce enough of the tight antibody to overcome the infection, meanwhile they’ll show symptoms
Describe memory cells
After being exposed to an antigen, both t and b lymphocytes produce memory cells which remain in the body for a long time. Memory t cells remember the specific antigen and will recognise it. Memory b lymphocytes remember the specific antibody needed to bind to the antigen.
