Topic 6B- Microorganisms And Immunity

Question 1

Name the structures found in bacteria

Answer 1

Flagellum
Pili
Capsule
Chromosomal DNA
Plasmids DNA
Ribosomes
Cell wall
Plasma membrane
Mesosomes
Cytoplasm

Question 2

Name the structures present in a virus

Answer 2

Attachment proteins
Envelope
Capsid
RNA or DNA (RNA in retro viruses such as HIV)
Proteins

Question 3

What is the definition of a pathogen?

Answer 3

Any organisms which cause infectious diseases

Question 4

What does HIV do to the immune system?

Answer 4

It uses T helper cells to replicate, and it bursts out of them destroying them. This reduced T helper cell numbers, which weakens the immune system.

Question 5

How does HIV replicate inside cells?

Answer 5

It attaches to T helper cells using attachment proteins. The capsid is inserted into the cell, where it uncoats and releases its genetic material (RNA). Reverse transcriptase creates a copy of DNA using the viral RNA as a template. This then forms a double strand of DNA. This is inserted into the host DNA, where is it transcribed and translated into viral proteins. This will form new viral components, which will form new viruses, which then bud out of the T helper cell- destroying it.

Question 6

What is the latency period?

Answer 6

A period where the number of HIV cells replicating decreases, and therefore there symptoms also disappear.

Question 7

HIV causes AIDS, what are the symptoms of AIDS?

Answer 7

Minor infections:
ears
nose
genitals (here are the mucosal areas)
persistent coughing.
More serious:
Chronic diarrhoea
Severe bacterial infections
Tuberculosis
Fatal:
Brain parasites
Respiratory fungal infections

Question 8

How does TB infect the immune system?

Answer 8

By surviving and replicating inside phagocytes

Question 9

What are Tubercles?
How can TB become active again?

Answer 9

Areas within the lungs where TB is sealed off by the immune system.

When the immune system becomes weakened and these tubercles aren’t maintained.

Question 10

What are the symptoms of TB?

Answer 10

Initial:
Fever and weakness (due to lung inflammation)
Developmental:
Damage to the lungs leading to respiratory failure.
Spread to other organs, such as liver or kidneys, leading to organ failure.

Question 11

Where can pathogens enter into the body?

Answer 11

Through cuts in the skin

Through respiratory system during inhalation through nose

Through the digestive system via contaminated food or drink

Through mucosal surfaces in the nose, ears, mouth or genitals.

Question 12

What are the barriers to prevent infection?

Answer 12

Stomach acid- acidic condition kills infectious material

Lysozyme (tears)- secreted at mucosal surfaces, where perforin perforates the infectious cell causing lysis.

Skin and gut flora- flora are naturally occurring organisms on the surface of the skin and gut. They compete with pathogens for nutrients and space, and because there is so many of them, they tend to outcompete and the pathogens struggle to grow.

Skin- it’s a physical barrier. If it breaks they can enter the blood, but it clots to prevent them from doing so.

Question 13

What is the non specific immune response?

Answer 13

It is a respond which occurs in the same way for all microorganisms, it is not specific to the antigens on the surface of the microorganism surface.

It attacks the microorganisms straight away.

Question 14

What are the three types of non-specific immune response?

Answer 14

Inflammation
Phagocytosis
Lysozyme action
Interferons

Question 15

Describe what happens during inflammation?

What are the characteristics of this response?

Answer 15

Histamine released
Vasodilation occurs and increased permeability.
More white blood cells go to the area of infection, so more phagocytosis occurs of pathogens.

Swollen, red, warm and painful areas.

Question 16

What are the jobs or inteferons?

What do they do?

Answer 16

They are anti viral proteins which prevent viruses from spreading to uninfected cells.

They prevent viral replication but inhibiting the viral proteins from being produced.

Stimulate specific immune response to kill pathogenic microorganisms.

They stimulate other non-specific immune responses, such as inflammation.

Question 17

How do phagocytosis and lysozyme action work?

Answer 17

The phagocyte recognises the foreign antigens. It moves around the pathogen, engulfing it. This creates a phagosome/phagocytic vacuole. A lysosome containing lysozyme will then fuse with this to form a phagolysozome. The lysozymes will then break down the pathogen, and the phagocyte will use MHCS proteins to become antigen presenting cells.

Question 18

What is the specific immune response?

Answer 18

An antigen-specific response which produces antibodies aimed at particular antigens.

Question 19

How do phagocytes activate T cells?

Answer 19

APCs have complementary antigens on their surface to the CD4 receptors on the surface of the T cells. The CD4 receptors bind to the antigens and become activated. Here they divide to produce clones of themselves.

Question 20

What are the 3 different types of T cells?

Answer 20

T helper cells
T killer cells
T memory cells

Question 21

What do T helper Cells do?

Answer 21

Activate B cells and T killer cells, and increase phagocytic activity.

The T helper Cells release cytokines, which are chemicals that stimulate:

B cells to become activated, which then become memory B cells and effector B cells which differentiate to become plasma B cells. Plasma B cells release antibodies to those antigens.

T killer cells to differentiate so to increase in numbers.

And increase phagocytic activity, so that more APCs can be made and the cycle can continue.

Question 22

T killer cells are a part of the ___ response?

B cells are part of the ______ response?

Answer 22

Cell-mediated

Humoral

Question 23

When an immune cell becomes activated, what two cell types do they take?

Answer 23

Memory cells- for a secondary immune response

Active cells- for the purpose of ridding the pathogens.

Question 24

Which cells release antibodies?

Answer 24

Plasma B cells

Question 25

What can antibodies do?

Answer 25

Prevent infection- surround pathogens by binding to all antigens to make the pathogens unable to bind to new human cells Opsonisation- marking a pathogen for destruction by allowing phagocytes to reach the pathogen and engulf it Act as antitoxins- neutralise toxins by binding to them, preventing their effect on human cells. The toxin-antibody complex is then phagocytosed. Agglutinating- each antibody has two binding sites to antigens, so this means antibodies can link pathogens together and therefore clump them together. This means that when a phagocytic cell arrives, it can engulf many pathogens at once.

Question 26

Antibodies can be membrane bound or secreted. Describe the differences between them.

Answer 26

Membrane bound: Attached to a B cell Extra section of heavy chain protein which anchors it to B cells Secreted: Free from any attachment Don’t have extra section on the heavy chain protein which anchors them to the B cell. Both have slightly different heavy chain structures.

Question 27

What are: Exons Introns

Answer 27

Parts of the DNA sequence which DO code for amino acids Parts of the DNA sequence which DO NOT code for amino acids “Exons are on, introns are not”

Question 28

What is splicing? What is alternative splicing?

Answer 28

The process by which the dna sequence is transcribed to pre-mRNA, and it is spliced (introns (non coding DNA) is removed leaving exons). Alternative splicing is just where some additional exons may be removed, which forms a different mRNA strand- producing a different amino acid structure and therefore proteins. This is what happens for membrane and secreted antibodies, the part of the heavy chain which isn’t present on the secreted antibody is left out when the exon coding for it is removed.

Question 29

What does a non specific and specific immune response together make?

Answer 29

A primary immune response

Question 30

Why is the primary immune response slow?

Answer 30

There haven’t been many B cells created yet, so there aren’t any antibodies made to bind to the pathogens antigens. Once there is enough, the antibodies will be able to overcome the infection

Question 31

What types of immunity are there?

Answer 31

Active: your own immune system is making antibodies as a result of a foreign presence of antigens from a pathogen in your system. Natural- producing antibodies when having a disease Artificial- producing antibodies as a result of a vaccine (attenuated versions of the pathogens) Passive: this is when you’re given antibodies from a different organism m Natural- from breast milk Artificial- from being injected with antibodies

Question 32

What are the benefits of using vaccines which may be even better than the bodies immune system?

Answer 32

The time taken for the body to produce B cells may allow the symptoms of the disease to develop. With a vaccine, this is less likely to happen. Vaccines contain antigens which stimulate a primary immune response without actually causing the disease, meaning that you become immune without actually getting any symptoms of the disease.

Question 33

What is the evolutionary race?

Answer 33

The struggle between pathogens and their hosts to have more superior mechanisms to overpower each other.

Question 34

What is HIVs evasion mechanism to our immune system?

Answer 34

It has constantly mutating antigens (antigenic mutation), forming new strains of the virus. This means the body can’t form immunity against the virus. It kills immune cells in order to replicate, so with less immune cells, the virus is harder to detect. It also disrupts antigen presentation in phagocytic cells, which can prevent immune system cells from recognising the disease and giving an immune response.

Question 35

What are TBs evasion mechanisms?

Answer 35

It produces a thick wax around its cell wall, which prevents lysozyme from being able to break down it. It can then reproduce undetected in the phagocytic cells. It also disrupts antigen presentation, affecting immune responses in other immune cells from killing infected cells.

Question 36

What are antibiotics?

Answer 36

Chemicals that kill or inhibit the growth of microorganisms.

Question 37

What are the different types of antibiotics?

Answer 37

Bacteriocidal- kill the bacteria Bacteriostatic- inhibit the growth of bacteria

Question 38

How do antibiotics work? How don’t they affect human cells or viruses?

Answer 38

The affect the bacteria’s metabolism. They do this by: Inhibiting enzymes needed for cell wall maintenance. This can lead to cell lysis if pressure inside the cell increases too high due to osmosis. Inhibiting protein production by binding to bacterial ribosomes. Since all enzymes are proteins, enzyme production will be affected, so important metabolic processes such as growth and development will be affected. They don’t affect human cells as human cells are eukaryotic and don’t have cell walls, so there are no enzymes to affect in this nature. Additionally, human cells have 80S ribosomes which are different to 70S ribosomes, so they’re no effected. Viruses don’t have ribosomes or cell walls, so bacteria don’t have an affect on them.

Question 39

Hospital acquired infections are transmitted by poor hygiene, how can this be minimised?

Answer 39

Regular hand washing of staff and patients Equipments and surface should be disinfected after every use. People with hospital acquired infections should be moved to isolation wards to minimise the risk of infection.

Question 40

Why are antibiotic resistant pathogens commonly found in hospitals?

Answer 40

As there are more antibiotics used in hospitals, so there is a higher probability of resistance being evolved in the pathogens.

Question 41

What codes of practice have been developed to prevent and control the development of antibiotic resistant infections/pathogens?

Answer 41

Doctors shouldn’t provide antibiotics for minor bacterial infections Doctors should provide narrow spectrum antibiotics instead of broad spectrum antibiotics Doctors should rotate the use of different antibiotics, to lower to chance of resistance being evolved. Patients should take the antibiotics for the full cycle, to prevent the accumulation of just the highly resistant bacteria. These are much more difficult to manage.