Disease And Immunity

Question 1

What is a pathogen?

Answer 1

A pathogen is a microorganism that causes disease.

Question 2

Name three types of pathogens

Answer 2

Bacteria, Fungus, viruses

Question 3

State two ways in which pathogens can cause disease

Answer 3

By releasing toxins
Damaginh host cells

Question 4

What is the difference between specific and non specifoc responses to disease?

Answer 4

Specific is much slower (yet quicker after re-infection)
Specific is only affective against a specific pathogen, non- specific works on a range of pathogens, and always uses the same response
Non-specific is present from birth, specific isnt

Question 5

What is an antigen?

Answer 5

A foreign protein that stimulates an immune response and the production of antibodies.

Question 6

How can a cell identify a virus?

Answer 6

Via their specifoc antigens on the surface of the virus, that are specific to each molecule

Question 7

Name a non specifoc immune response

Answer 7

Phagocytosis

Question 8

Describe the stages of phagocytosis

Answer 8

A phagocyte regocnises and binds to the specific antigen on the pathogen.
It engulfs the pathogen, enclosing it in a vesicle.
Lysosomes fuse with the vesicle, and its hydrolytoc enzymes damage the bacteria cell walls
The enzymes digest the pathogen by hydrolysis of its molecules
The phagocyte places the pathogens antigens on its surface membrane, becoming an antigen presenting cell.

Question 9

How can a cell become an antigen presenting cells?

Answer 9

Cells that:
Are infected by a virus
An abnormal cell that has become cancerous
A phagocyte that has just engulfed and hydrolysed a pathogen

Question 10

What is the difference between cellular and humoral specific immune responses?

Answer 10

Humoral is mediated by B cells, cellular is mediated by specific T- helper cells
Humoral produces and releases antibodies, cellular destroys infected cells

Question 11

Describe the process of the cellular immune response

Answer 11

A specific t-helper cell binds to an antigen on the antigen presenting cell, via its complimentary receptors
This stimulates the specific T-helper cell to divide by mitosis, to produce more T-helper cells and memory cells
The T-helper cells release cytokines, which stimulate specific cytotoxic T- cells to divode by mitosis
The cytotoxic cells release perforin, which destroys the infected cell by osmotoc lysis.

Question 12

Describe the process of the humoral immune response

Answer 12

The specofc B cell binds to an antigen on the pathogen, via its complimentary receptors
Cytokines released by specifoc Thelper cells activate the B cells, causing them divide by mitosis to prodice cells that differentiate into plasma cells and memory cells.
Plasma cells produce and release antibodies
Memory cells remain in the body, and upon second exposure prodice plasma cells that release more antibodies more rapidly

Question 13

How many antibodies can plasma cells produce per second?

Answer 13

Around 200

Question 14

What are antibodies?

Answer 14

Proteins synthesised by specifoc plasma B cells.
They have a specific tertuary structure, that is complimentary to a particular antigen

Question 15

What is the role of antibodies?

Answer 15

Antibodies can bind to specific antigens (due to their complimentary tertiary structure) to form an antigen- antibody complex.
They then neutralise the pathogens, by clumping them together, allowing phagocytes to engulf more pathogens. This is called agglutination

Question 16

What are monoclonal antobodies?

Answer 16

Antibodies that are produced by the same specific B-cell/ plasma cells. They have the same tertiary structure and will bond to the same antigen

Question 17

What are five uses of monoclonal antibodies?

Answer 17

Medical diagnosis
Pregnancy testing
Targeted drug treatments
Drug testing
Covid testing

Question 18

Explain the process of the Elisa test is

Answer 18

A container is coated in monoclonal antibodies, specific to the antigen being tested for
The sample being tested is added to the container. If the antigen is present it will bind to the monoclonal antibodies.
The container is washed to remove any unbound antigens
A second monoclonal antibody with an emzyme attached is added, and will bind to another site of the antigens
The container is washed again
The substrate to the enzyme is added, and hydrolysed (if the antigen and therefore enzyme is present). This will cause a colour change, indicating a positive result

Question 19

What is passive immunity?

Answer 19

Where antibodies are aquired from an outside source. It give immediate immunity yet the effect is short lived

Question 20

What is active immunity?

Answer 20

Immunity stimulated by the production of antibodies
It is not immediate as memory cells need to be made, yet this means the effect is long lasting.
It can be aquired naturally (by pathogens) lr artificially (vaccinations)

Question 21

What are vaccinations?

Answer 21

The introduction of an antigen into an organism, with the intention of making them immune to a specifoc disease

Question 22

Explain how vaccinations provide immunity for a disease

Answer 22

A vaccination contains a specific inactive/ weakened antigen
The antigen will be displayed on an antigen presenting cell.
Specific Th cells will bind to the antigen, and release cytokines
Cytokines will activate specific B cells to divide by mitosis, producing memory cells and plasma cells
Upon second exposure to the same antigen, memory celld will prodice olasma cells, whoch will produce and release more antibodies more rapidly
The pathogen is therefpre destroyed before symptoms start

Question 23

What makes a vaccination programme successful?

Answer 23

The vaccine must have very few side effects
Must have means of administration
Easily stored and transported
Economically available in larger quantities

Question 24

What is heard immunity?

Answer 24

Where around 90% of the population are vaccinated against a particular disease, which prevents the spread of the disease to people who are not vaccinated/ immune

Question 25

What is HIV?

Answer 25

A virus that can cause AIDS (acquired immune deficiency syndrome)

Question 26

State the features of a HIV virus

Answer 26

A capsid that contains genetic material (RNA) and the enzyme reverse transcriptase
Attachment proteins
Lipid envelope

Question 27

Explain how HIV replicates, once it has infected an organism

Answer 27

Attachement proteins bind to the specific complimentary receptors on T-helper cells
The capsid (containing RNA and reverse transcriptase) is injected into cell, the RNA and enzyme are released
Reverse transcriptase is used to make a complimentary strand of DNA, using viral RNA as a template
Double stranded DNA is made from this, and incorporated in the t cells own DNA.
Viral DNA used to make new Viral proteins, which are made into new viruses inside cell and released.

Question 28

Explain the development of aids

Answer 28

The replication and release of HIV viruses lead to the destruction of T helper, so their numbers decrease
Fewer T helper cells means fewer B cells, cytotoxic T cells and phagocytes are activated
The bodys immune response is reduced, less infected cells are destroyed.
Organism becomes more susceptible to other infections that can cause desth

Question 29

State three typical symptoms of AIDS

Answer 29

Lung infections, weight loss, diarrhoea

Question 30

How can HIV be treated?

Answer 30

Using a combination of antiviral drugs

Question 31

Explain why HIV cannot be trated with antibiotics

Answer 31

They are viruses, not bacterial cells
They dont contain the structures that are targeted by antibiotics
They infect body cells, so the antibiotics would also damage normal cells
Ciruses have a different metabolism