Fichas
The Immune System
Fichas del conjunto (40)
- 1What happens when a pathogen enters the body?Foreign antigens trigger an immune system
When a pathogen invades the body, the antigens on its cell surface are identified as foreign which activate cells in the immune system. - 2What are antigens?These are molecules (usually proteins or polysaccharides) found in the surface of cells.
- 3What are the two stages in immune response?These are non-specific e.g. the same way for all microorganisms and antigen specific - aimed at specific pathogens. This involves white blood cells called T and B lymphocytes.
- 4What are the four main stages in the immune response?1) Phagocytes engulf pathogens
2) Phagocytes activate T-lymphocytes
3) T-lymphocytes activate B-lymphocytes, which divide into plasma cells
4) Plasma cells make more antibodies to a specific antigen - 5What is a phagocyte?A phagocyte is a type of white blood cell that carries out phagocytosis (this is engulfment of pathogens)
- 6Where are phagocytes found?In the blood and in tissues
- 7What type of immune response do phagocytes carry out?Non-specific immune responses
- 8How do phagocytes work?It recognises the antigen on a pathogen. The cytoplasm of the phagocyte moves round the pathogen, engulfing it. This may be made easier by the presence of opsonins.
The pathogen is now contained in a phagosome (a type of vesicle in the cytoplasm of the phagocyte). A lysosome (an organelle that contains digestive enzymes) fuses with a phagosome. The enzyme breaks down the pathogen.
The phagocyte then present the pathogens antigens. It sticks the antigens on it's surface to activate other immune system cells.
When a phagocyte does this, it is acting as an antigen presenting cell (APC). - 9What are opsonins?These are molecules in the blood that attach to foreign antigens to aid phagocytosis
- 10Explain how opsonins workThey work in different ways. Some hide the negative charges on the membrane of the pathogen, making it easier for the negatively charged phagocyte to get closer to the pathogen.
- 11What are neutrophils?These are types of phagocytes. They are the first white blood cells to respond to a pathogen in the body. They move towards a wound in response to signals in cytokines (proteins that act as a messenger molecule). The cytokines are released by cells at the site of the wound.
- 12What is a T-lymphocyte?This is another type of white blood cell
- 13How do phagocytes activate T-lymphocytes? (I)They're surface is covered by receptors. Each one binds to antigens present by APCs. Each T-lymphacyte has a different receptor on its surface and when the receptor meets a complementary antigen, it binds to it, so each T-lymphocyte will bind to a different antigen.
- 14How do phagocytes activate T-lymphocytes? (II)This then activates the T-lymphocyte and the process is called clonal selection. The T-lymphocyte then undergoes clonal expansion - it divides to produce clones of itself. Different types of T-lymphocytes carry out different functions.
- 15What are the different types of activated T-lymphocytes?1) T-helper cells
2)T-killer cells
3) T-regulator cells - 16What do T-helper cells do?They release substances to activate B-lymphacytes and T-killer cells
- 17What do T-killer cells do?These attach to and kill cells that are infected with a virus
- 18What do T-regulatory cells do?These suppress the immune response from other white blood cells. This helps to stop immune system cells from mistakenly attacking the host's body cells.
Some activated T-lymphacyte cells become memory cells - 19How do T-lymphacytes activate B-lymphacytes?B-lymphacytes are another type of white blood cells which are covered with proteins called antibodies. Antibodies bind to antigens to form an antigen-antibody complex.
Each B-lymphocyte has a different shaped antibody on its surface. - 20What happens when the antibody on the surface of a B-lymphacyte meets a complementary shaped antigen?It binds with it - so each B-lymphocyte will bind to a different antigen.
This together with substances released from T-helper cells, activates the B-lymphoctye. This process is an example f clonal selection.
The activated B-lymphocyte divides by mitosis into plasma and memory cells (clonal expansion) - 21What is cell signalling?This is how cells communicate. A cell may release a substance that binds to the receptors on another cell and cause a response of some kind.
- 22Why is cell signalling important in the immune response?As it helps to activate all the different types of white blood cells that are needed
- 23Give an example of how cell signalling worksT-helper cells release interleukins (a type of cytokine) that bind to receptors on B-lymphocytes. This activates the B-lymphocyte that there's a pathogen in the body.
- 24How do plasma cells make more antibodies to a specific antigen?Plasma cells are clones of the B-lymphocytes (identical to the B-lymphocyte). They secrete loads of the antibody specific to the antigen into the blood. These antibodies bind to the antigens on the surface of the pathogen to form lots of antigen-antibody complexes.
- 25Learn the structure of an antibody (on the middle right of page 99)Learn the structure of an antibody (on the middle right of page 99)
- 26Describe the structure of an antigen-antibody complex?The variable region of the antibody form the antigen binding site. The shape of the variable region is complementary to a particular antigen. The hinge region allows flexibility when the antibody binds to the antigen. The constant region allows binding to receptors on immune system cells (phagocytes). The constant region is the same in all antibodies. The disulphide bridge (a type of bond) holds the polypeptide chain of the protein together.
- 27Explain the different methods by which antibodies help to clear an infectionAgglutinating pathogens
Neutralising toxins
Preventing the pathogen from binding to human cells - 28Explain how agglutinating pathogens helps to clear an infectionEach antibody has two binding sites, so an antibody can bind to two pathogens at the same time - the pathogens become clumped together. Phagocytes then bind to the antibodies and phagocytose a lot of pathogens all at once. Antibodies that work in this way are called agglutinins.
- 29Explain how neutralising toxins helps to clear an infectionLike antigens, toxins have different shapes. Antibodies called antitoxins can bind to the toxins produced by pathogens. This prevents the toxins from affecting human cells, so the toxins are neutralised (inactivated). The toxin antibody complexes phagocytosed.
- 30Explain how preventing the pathogen from binding to human cells helps to clear an infectionWhen antibodies bind to the antigens on pathogens, they may block the cell surface receptors that the pathogens need to bind to the host cells. This means that the pathogen can't attach to or infect the host cells.
- 31What is the primary response?When a pathogen enters the body for the first time, the antigens on it's surface activate the immune system. This is called the primary response.
- 32Why is the primary response slow?As there aren't many B-lymphocytes that can make the antibody needed to bind to it.
Eventually, the body will produce enough of the right antibody to overcome the infection. Meanwhile the infected person will show symptoms of the disease.
After being exposed to the antigen, both T and B lymphocytes produce memory cells which remain in the body for s long time.
Memory T lymphocytes remember the specific antigen and will recognise it a second time round. Memory B lymphocytes record the specific antibodies needed to bind to the antigen.
The person is now immune - - 33Explain the primary responseEventually, the body will produce enough of the right antibody to overcome the infection. Meanwhile the infected person will show symptoms of the disease.
After being exposed to the antigen, both T and B lymphocytes produce memory cells which remain in the body for s long time.
Memory T lymphocytes remember the specific antigen and will recognise it a second time round. Memory B lymphocytes record the specific
antigen and will recognise it a second time round. Memory B lymphocytes record the specific antibodies needed to bind to the antigen.
The person is now immune - Their immune system has the ability to respond quickly to a second infection. - 34What is the secondary response?If the same pathogen enters the body again, the immune system will produce a quicker, stronger immune response - the secondary response.
- 35Explain the secondary responseClonal selection happens faster. Memory B lymphocytes are activated and divide into plasma cells that produce the right antibody to the right antigen. Memory T - lymphocytes are activated and divide into the correct type of T lymphocytes to kill the cell carrying the antigen.
The secondary response gets the pathogen before you begin to show any symptoms. - 36Learn the table and the graph at the bottom of page 100Learn the table and the graph at the bottom of page 100
- 37What is a blood smear?This is a sample of blood smeared over a microscope slide
- 38Why are stains added to a sample?To make the different cells easy to see
- 39Explain how to examine a blood smearWhen looking at a blood smear, your likely to see red blood cells, white blood cells and platelets (tiny fragments of cells involved in blood clotting). Some types of white blood cells have granules in their cytoplasm (so they look grainy) and others don't.
- 40Learn the diagram at the bottom of page 101Learn the diagram at the bottom of page 101
Información
- Descripción
- AS - Level (Disease and the Immune System) Biology Fichas sobre The Immune System, creado por Tom Baker el 17/04/2016.
- Creado por
- Tom Baker
- Visitas
- 0
- Valoración