Immunity

Question 1

What is a pathogen?

Answer 1

Microorganisms that can cause disease.

Question 2

What are the four different types of pathogens?

Answer 2

1. Bacteria.
2. Fungi.
3. Protists.
4. Viruses.

Question 3

How do bacteria cause disease?

Answer 3

They release toxins that damage body cells.

Question 4

How do viruses cause disease?

Answer 4

They use host cells to replicate before bursting out and destroying cells.

Question 5

How do protists cause disease?

Answer 5

They take over cells and break them open.

Question 6

How do fungi cause disease?

Answer 6

Digest living cells to destroy them and some release toxins.

Question 7

What is the difference between non-specific and specific defense mechanisms?

Answer 7

Non-specific responses to all pathogens are the same, and specific responses produce a different response for every pathogen.

Question 8

What physical and chemical barriers does the body use to prevent infection?

Answer 8

1. The skin acts as a physical barrier to block pathogens from entering the body. It also produces sebum that inhibits the growth of pathogens.
2. The mucus produced by the body traps pathogens and prevents them from entering the body.
3. Eyelashes and nose hairs trap pathogens and prevent them from entering the body.
4. Tears have enzymes that kill pathogens and prevent them from entering the eye.

Question 9

What are antigens?

Answer 9

A protein on the surface of a pathogen that stimulates an immune response.

Question 10

Apart from pathogens what other cells and molecules can the immune system identify?

Answer 10

1. Abnormal body cells like cancerous or infected cells.
2. Toxins.
3. Foreign cells.

Question 11

How does phagocytosis occur?

Answer 11

1. The pathogens release toxins that attract the phagocytes to them.
2. The phagocytes engulf the pathogens to form a phagosome. The vesicles then fuses with a lysosome.
3. The lysosome releases its lysozymes into the vesicle, which hydrolise the pathogens and kills them.
4. The phagocyte then displays the antigens of the pathogens on its cell membrane.

Question 12

Describe the cell-mediated response.

Answer 12

1. After phagocytosis the phagocytes display the antigens of a pathogen in their cell membrane.
2. The T-cells have receptors in their cell membrane that are specific to those antigens. Once the receptors bind to those antigens the T-cells divide by mitosis to form helper T-cells and cytotoxic T-cells.
3. Helper T-cells activate phagocytosis, cytotoxic T-cells and B-cells.
4. Cytotoxic T-cells kill abnormal and foreign cells.

Question 13

Describe the humoral response.

Answer 13

1. The B-cells have Antibodies on their cell membrane that are complementary to a specific pathogen. They also have receptors that are complementary to chemical releases by helper T-cells that activate it.
2. Once the Antibodies bind to that pathogen and the B-cells are activated by chemicals released by helper T-cells they divide by mitosis to form plasma and memory cells.
3. Plasma cells secrete Antibodies, and memory cells remain in the body for a long time the Antibodies on their cell membrane bind to that pathogen again. They divide rapidly to form plasma cells that secret Antibodies.

Question 14

Why is the primary immune response much slower compared to the secondary immune response?

Answer 14

The primary response is slow because there are few B-cells with Antibodies complementary to the specific antigen on the pathogen and it takes time for the B-cells to divide into plasma cells that secrete Antibodies. The secondary response is faster because the memory cells that were produced during the primary response are present and they can divide rapidly to form plasma cells once the antibody on these cells binds to the antigens on the pathogen.

Question 15

Draw and label an antibody. What is an antibody?

Answer 15

An antigen-binding immunoglobulin, produced by B cells, that functions as the effector in an immune response.

Question 16

How do antibodies help fight infection

Answer 16

The antigen bidding site on the Antibodies bind to antigens on pathogens ans cause them them to stick together. This makes it easier for pathogens to engulf and hydrolyse the pathogens.

Question 17

Why are Antibodies specific to a particular antigen?

Answer 17

The Antibodies have a specific tertiary structure meaning they are only complementary to a specific antigen and they can only form an antibody-antigen complex with that antigen.

Question 18

What are monoclonal Antibodies?

Answer 18

Antibodies made from identical plasma cells.

Question 19

What medical purposes do monoclonal antibodies have?

Answer 19

1. Bringing therapeutic drugs to cells.
2. Pregnancy tests.
3. Diagnosis of diseases using ELISA tests.

Question 20

What is a positive ELISA test used for?

Answer 20

To detect whether the patient has the Antibodies that bind to a specific antigen.

Question 21

Describe a positive ELISA test.

Answer 21

1. The antigen is added to wells in a plate.
2. A sample of the patient’s blood plasma is placed in the plate, and if the first antibody that is complementary to the specific antigen is present, then it will bind to it. The antigen and antibody form a complex.
3. The plate is washed to remove any unbound Antibodies.
4. A second antibody is added, and if the first antibody is present, then the second antibody will bind to the antigen and form a complex. This antibody has an enzyme attached to it.
5. If the second antibody has bound once the substrate is added there should be a colour change.

Question 22

What is active immunity?

Answer 22

When the body makes its own Antibodies after being exposed to a pathogen.

Question 23

What are examples of natural and artificial active Immunity?

Answer 23

1. Natural: The body’s immune system producing Antibodies after being exposed to a pathogen.
2. Artifical: The body producing Antibodies after a vaccine.

Question 24

What is passive Immunity?

Answer 24

An individual is given Antibodies that come from another organism.

Question 25

What are examples of natural and artificial passive Immunity?

Answer 25

1. Natural: A mother transferring her Antibodies to her baby through breast milk. 2. Artifical: Monoclonal Antibodies.

Question 26

What are vaccinations?

Answer 26

When a dead organic inactive pathogen is injected into the person in order to trigger an immune response.

Question 27

What ate the factors taken into account when making and distributing vaccines?

Answer 27

1. The vaccine must be affordable and available in large amounts for mass immunisation. 2. They must have few side effects. 3. Whether there are necessary resources for production, storage and transportation. 4. Whether there are enough trained healthcare workers to give the vaccines in a proper and timely manner. 5. Whether herd Immunity can be reached.

Question 28

What is herd Immunity?

Answer 28

By vaccinating as many people as possible most people within the population will be immune to the diseases and won't be able to pass it to others. This protects people who can't get vaccines from being infected.

Question 29

Why do vaccines not completely eliminate diseases?

Answer 29

1. People with weak immune systems, like babies and the Elderly, may not be able to withstand vaccines and build up an immune response. 2. Pathogen mutation and antigenic variability. 3. Pathogen variety means that a vaccine could not help deal with all the different types of a certain disease like colds. 4. Vaccine objections.

Question 30

What is antigenetic variability and how does it affect how well vaccines can help manage diseases?

Answer 30

It is when the antigen on a pathogen changes. It means that the immune system will no longer recognise the antigens and the memory cells won't be activated by the antigens on the new strain of pathogen. This means that the immune system won't be able to deal with illness before the symptoms start showing up.

Question 31

How do antibiotics kill bacteria?

Answer 31

They target the metabolic reactions of the bacteria, like stopping them from forming cell walls or disrupting enzyme activity.

Question 32

Why do antibiotics not work on viruses?

Answer 32

Antibiotics stop the metabolic reactions of bacteria, but since viruses don't have any cell structures and rely on their host cells' metabolic reactions the antibiotics can't disrupt these without causing harm to healthy human cells.

Question 33

How do bacteria develop antibiotic resistance?

Answer 33

1. A genetic mutation occurs, which means that some bacteria have an allele that makes them resistant to antibiotics. 2. These bacteria survive and can reproduce and pass on that resistance allele to their offspring. Their offspring are also more likely to survive, reproduce and pass on that allele to the next generation. Over time, the frequency of that allele increases until almost all of them have that gene.

Question 34

Draw the structure of a HIV virus.

Question 35

Describe how the HIV virus replicates.

Answer 35

1. HIV has attachment proteins on their envelope that are complementary to a specific receptor on the cell membrane of helper T-cells. 2. Once the proteins and receptors bind together the contents of the virus are inserted into the helper T-cell. 3. The reverse transcriptase turns viral RNA into viral DNA, and the viral DNA is inserted into the host cells' DNA. 4. The host cell then transcribed the viral DNA into viral mRNA. 5. This is then translated to form the proteins needed to make new viruses.

Question 36

How does HIV cause disease?

Answer 36

The HIV virus destroys helper T-cells, and this causes the immune system to fail as there are fewer helper T-cells available to activate phagocytosis of pathogens, cytotoxic T-cells and activate the formation of plasma cells that release Antibodies. This leads to the formation of AIDS, which is when the person is not able to fight infections and certain infections can lead to death.

Question 37

What is the treatment for HIV?

Answer 37

HIV and AIDS are incurable. However, antiretroviral drugs can reduce viral replication to the point that the infected person experiences no symptoms and can't transmit the virus.