Study sets, textbooks, questions
Upgrade to remove ads
AQA A-Level Biology (new spec) Unit 2C - Cells and The Immune System
Terms in this set (47)
Molecules that can generate a immune response when detected by the body
Organisms that cause disease
Define abnormal body cells
Cancerous or pathogen-infected cells have abnormal antigens
Poisons which are molecules and can be produced by pathogens
What happens with blood transfusions?
Cells will have antigens which are different from our own, so this triggers an immune response. This is why blood is matched on ABO blood group
Define a phagocyte
A type of white blood cell found in the blood, are the first cells to respond to an immune trigger
How does phagocytosis work?
A phagocyte recognises foreign antigens, the cytoplasm engulfs the pathogen so it's contained in a phagocytic vacuole, a lysosome fuses with the vacuole and the lysozymes break down the pathogen. The phagocyte presents the pathogen's antigens to active other immune cells
What are T-cells?
A white blood cell with receptor proteins that bind to complementary antigens presented by phagocytes
What are the 2 types of T-cells?
Helper t-cells (Th) and cytotoxic t-cells (Tc)
What do helper t-cells do?
Release chemical signals that activate and stimulate Tc cells and phagocytes. It also activates B-Cells
What do cytotoxic t-cells do?
Kill abnormal and foreign cells by releasing a chemical which perforates the CSM, making the cell kill itself
What are B-cells?
A white blood cell covered in antibodies, each b-cell has a different antibody on it so they can bind to complimentary antigens to form antigen-antibody complexes
What happens during clonal selection?
An antibody on a B-cell binds to a complimentary antigen on a pathogen, activating the B-cell, which divides into plasma cells
What do plasma cells do?
Release antibodies specific to the antigen to form antigen-antibody complexes
What is agglutination?
Where pathogens become grouped together as antibodies can bind to 2 antigens. Phagocytes engulf many antigen-antibody complexes at once, leading to the destruction of the pathogen
What are antibodies?
Proteins, made of chains of amino acids. It's specific because of the variable regions which form the binding sites, meaning that they have unique tertiary structures. All antibodies have the same constant region
What is the cellular immune response?
T-cells and phagocytes
What is the humoral immune response?
B-cells, clonal selection and the production of monoclonal antibodies
What happens during the primary immune response?
An pathogen enters the body for the first time. The primary response is slow because there aren't enough B-cells to make antibodies needed to bind to the antigens. The infected person will show symptoms. After being exposed to the antigen, memory t-cells (which remember the antigen and will recognise it) and memory b-cells (which remember the antibodies and will make them quicker) are produced, making the person immune
What happens during the secondary immune response?
If the same pathogen enters the body again, the immune system will produce a quicker, stronger immune response. Clonal selection happens faster and antibodies are released sooner. The person won't show symptoms
Define active immunity
When the immune system works to produce its own antibodies after being stimulated by an antigen
Give a natural and artificial method of gaining active immunity
Natural - become immune after catching a disease, artificial - become immune after a vaccine
Define passive immunity
Being given antibodies made in a different organism
Give a natural and artificial method of gaining passive immunity
Natural - when a baby becomes immune due to antibodies received from it's mother through the placenta and umbilical cord, artificial - become immune after being injected with antibodies from someone else
List 3 differences between active immunity and passive immunity
Active immunity: requires exposure to antigen, takes time for protection to develop, memory cells are produced. Passive immunity: doesn't require exposure to antigens, protection is immediate, memory cells aren't produced
What are vaccinations?
Injections that contain antigens that cause your body to produce memory cells against a particular pathogen, without the pathogen causing damaged
Define herd immunity
Those who are vaccinated are likely to protect those not vaccinated, as there's less chance of the disease occurring
What are the disadvantages of taking a vaccine orally?
It could be broken down by enzymes in the gut or the molecules could be too large to be absorbed into the blood
Why are booster vaccines given?
To make sure that more memory cells are produced and that the person is immune
What are some of the ethical issues surrounding vaccines?
All vaccines are tested on animals, which people disagree with. Testing on humans can be risky, volunteers may put themselves at unnecessary risk to prove that it works. If there was an epidemic of a new disease, people would rush to get a vaccine, and decisions would have to be made on who would be the first to get it
What is antigenic variation?
Where pathogens change their surface antigens so the immune system doesn't recognise the antigens, so memory cells won't work, even if you're infected with the same disease
Why does the influenza vaccine change every year?
This is due to antigenic variation. The antigens on the surface change regularly, resulting in constant vaccines as every year, there's a different strain
What can monoclonal antibodies be used for?
Medical diagnoses and pregnancy tests
How do pregnancy tests work?
They detect hCG in urine of pregnant women. The application area contains antibodies bound to a blue bead that are complimentary to the hCG protein, when urine is applied, hCG will bind to the antibodies, forming an antigen-antibody complex. The urine moves up the stick, carrying blue beads with it. The test strip contains immobilised amtibodies to hCG which bind to hCG if its detected, turning the strip blue, confirming pregnancy
What does the ELISA test detect?
Enzyme-Linked ImmunoSorbent Assay (ELISA) looks for specific antigens/antibodies. It can test for HIV/AIDS and allergies
Outline the direct ELISA test
Antigens form a patient sample is bound to a well in a well plate. A detection antibody that is complimentary to the antigen of interest is added. If the antigen is present, the antibody is immobilised, the well is washed to remove unbound antibodies. A substrate solution is added, and if the detection antibody is present, the enzyme reacts with the substrate to give a colour change
Outline the indirect ELISA test to diagnose HIV
The antigen is bound to a well, the sample of blood is added to the well so any antibodies for HIV can bind to the antigens. The well is washed out to remove unbound antibodies. A secondary antibody is added which binds to the HIV antibody, the well is washed again. A substrate solution is added to the well which will react with the enzyme on the secondary antibody if any remains, indicating the patient has HIV
Indicate ethical issues surrounding the use of monoclonal antibodies
Animals are used to produce the cells from which the monoclonal antibodies are produced, some people disagree with this
What is HIV?
Human Immunodeficiency Virus attacks the body's immune system. It eventually leads to AIDS (Acquired Immune Deficiency Syndrome), where the immune system eventually fails and you die from complications
How does HIV work?
It attacks Th cells, which act as the host cell for the virus. Th cells activate phagocytes, Tc cells and B cells, so those cells won't work, meaning an immune response can't be triggered
What happens during the initial infection period of HIV?
HIV replicates rapidly and the person may suffer extreme flu-like symptoms. After this, replication drops to a lower level, known as the latency period, where the person won't experience symptoms
What are the symptoms of AIDS?
People are classed as suffering with AIDS when their white blood cells drop below a certain level. The initial symptoms are minor infections of mucus membranes and recurring respiratory infections. As it progresses, the immune cells decrease, so they become more susceptible to severe bacterial infection and TB. During the late stages, people have very low immune cell levels, so can develop toxoplasmosis of the brain and candidasis of the repsiratory system.
What is the structure of HIV?
Has a spherical structure, made up of a core of RNA and proteins (including reverse transcriptase), a capsid, attachment proteins and an envelope made of membrane stolen from a previous host cell
How does HIV replicate?
The attachment proteins attach to a receptor molecule on the Th cell. The capsid is released into the cell where it released the RNA, reverse transcriptase makes complimentary DNA from the viral RNA template. Double stranded DNA is made and inserted into the human DNA. Host cell enzymes used to make viral proteins from the viral DNA found in the human DNA, the proteins are assembled into new viruses which infect new cells.
How do antibiotics kill bacteria?
They interfere with metabolic reactions by targeting enzymes and ribosomes.
Why can't antibiotics kill viruses?
They don't have their own enzymes and ribosomes, they use host cell enzymes
How can HIV be controlled?
Reduce the spread, always have protected sex and not sharing needles
Other sets by this creator
AQA Biology - Unit 2C - HIV And Viruses
Immune System Practice Questions
Adaptive immunity: Questions!
Immune System Test Questions