Option A - Immunology and disease Flashcards
(400 cards)
1
Q
What is the human body for a wide variety of microorganisms?
A
A host
2
Q
What is the human body a host for?
A
A wide variety of microorganisms
3
Q
Term for the human body being a host for a wide variety of microorganisms
A
The microflora of the body
4
Q
Microflora of the body
A
The wide variety of microorganisms in the human body
5
Q
Why is the term “microflora” used?
A
Flora = plants
Bacteria used to be thought to be microscopic plants
6
Q
Is all bacteria in the body bad?
A
No
7
Q
Do all microorganisms cause disease?
A
No
8
Q
What are our environments and body full of?
A
Microorganisms
9
Q
What do many species of bacteria and fungi have with the human body?
A
A symbiotic relationship
10
Q
What does the human body have a symbiotic relationship with a lot of?
A
Many species of bacteria and fungi
11
Q
What do bacteria and fungi obtain from the human body in the symbiotic relationship?
A
Habitat and food
12
Q
Services provided by many species of bacteria and fungi to the human body in the symbiotic relationship
A
Some gut bacteria aid digestion and absorption
Some provide vitamin K, a vitamin needed for blood clotting
On the outer surface of the skin, they outcompete pathogenic organisms
In the vagina, they produce lactic acid which prevents pathogenic growth
13
Q
What do some species of bacteria do in the vagina?
A
Produce lactic acid which prevents pathogenic growth
14
Q
What is vitamin K needed for?
A
Blood clotting
15
Q
Vitamin needed for blood clotting
A
Vitamin K
16
Q
What do bacteria and fungi do on the outer surface of the skin?
A
Outcompete pathogenic growth
17
Q
What type of cells are there the most of in the human body- bacterial cells or human cells?
A
Bacterial cells
18
Q
What’s the issue with some microorganisms? Explain
A
Some species are pathogenic or parasitic - they have the potential to cause disease if they secrete toxins or if their numbers increase too much
19
Q
When do pathogenic or parasitic bacteria cause disease?
A
If they secrete toxins or if their numbers increase too much
20
Q
What happens if pathogenic or parasitic species secrete toxins or if their numbers increase too much?
A
They have the potential to cause disease
21
Q
Pathogens
A
An organism that causes disease to its host
22
Q
An organism that causes disease to its host
A
Pathogen
23
Q
What s cholera caused by?
A
A Gram negative bacterium which is endemic in some areas of the world
24
Q
Endemic
A
The disease is always present at low areas in a particular region
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What does the cholera bacteria do?
Its toxins affect the gut lining causing watery diarrhoea leading to severe dehydration and frequently death
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What role do humans play in the spread of cholera?
They act as reservoirs or carriers and contaminate water supples in which the organism is transmitted
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Reservoirs of infection
Where a population of organisms are host to the pathogenic bacteria/pathogenic organism (i.e - where the bacteria lives)
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Reservoirs of infection for cholera
Humans
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What would a carrier of cholera do?
May be symptomless and spread the disease
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Where is the only place that cholera bacteria multiplied?
In the human host
31
How is cholera prevented?
By the treatment of water, good hygiene and the provision of clean drinking water
32
How is water purified to kill pathogens?
Using UV light or chlorine for example
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Possible treatment of cholera
Antibiotic treatment
34
What is the main treatment of cholera?
Rehydration
35
How do we rehydrate someone with chloera?
Electrolytes and glucose in clean water
36
Derivation of vaccine for chloera
Killed organism or possibly genetically engineered
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What would a vaccine do against cholera?
May provide temporary protection
38
How would cholera bacteria look when stained with Gram’s stain?
Characteristic curved rods (comma shaped)
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What type of bacterium is the cholera bacteria?
Gram negative
40
Causative agent of cholera
*Vibrio cholerae*
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Name for the bacteria that cases cholera
Vibrio cholerae
42
When are there concerns that cholera will spread?
In contaminated drinking water in developing areas or when a natural disaster occurs
43
Why would a natural disaster lead to an increase in the number of people with chloera?
The natural disaster will cause a collapse in the normal societal services so clean water cannot be provided
44
Explain exactly why cholera cases tend to increase following a natural disaster
The natural disaster will cause a collapse n the normal societal services so clean water cannot be provided
It’s therefore hard to obtain clean water to rehydrate to treat cholera and that water may be infected too, causing the cycle to repeat
45
What is the main think needed to treat chlolera and why?
Clean water
To rehydrate
46
Did cholera used to be a big deal?
Yes - it used to kill millions of people per year
47
How does *Vibro cholerae* cause cholera to happen?
By producing a toxin called choleragen
48
Toxin produced by vibrio cholerae
Choleragen
49
What does the toxin choleragen do?
Causes water loss in cells
50
Explain exactly how Vibrio cholerae producing choleragen leads to water loss in the cells
Choleragen raises the levels of intracellular cyclic AMP (cAMP) in the epithelial cells lining the gut
This reverses the action of the sodium and chloride pumps in the epithelial cell membrane
The cells actively pump Na+ and Cl- ions out and into the lumen of the gut
This causes a disturbance in the electrolyte balance of the body
High concentrations of salts build up in the lumen of the gut and this causes fluid loss from the body as a result of osmosis (the water potentials of the cells increase so large quantities of water leave the cell, leading to dehydration)
This fluid loss leads to circulatory collapse and possibly death
51
How does choleragen increase the levels of cAMP in epithelial cells?
The toxin activated Adeylate cyclase, and this causes cAMP to be synthesised
52
How is treatment of cholera with fluid replacement (rehydration fluid) done?
It’s either given orally or with a drip into the blood
53
What is TB caused by?
*Mycobacterium tuberculosis* infection
54
Bacteria that causes TB
*Mycobacterium tuberculosis*
55
What type of disease is TB?
Bacterial
56
Why is TB on the increase?
Partly Due to the link with the HIV epidemic
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When can TB be spread rapidly?
In overcrowded conditions
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How is TB transmitted?
In airborne droplets when infected people cough and sneeze
59
Explain how people with TB coughing and sneezing would lead to others catching TB
Sneezing projects fluid from the lungs onto surfaces that can be touched, and also the microscopic aerosol particles are water particles in which bacteria can live in. These stay in the air for a long time and can be breathed in.
60
What can be happen with the microscopic aerosol particles released when infected people cough and sneeze? Why?
They’re water particles in which bacteria can live in, so they stay in the air for a long time and can be breathed in
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What does the most common form of TB attack?
The lungs and neck lymph nodes
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Symptoms of TB
Coughing, chest pain, coughing up blood
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How is TB prevented?
By a BCG vaccination programme for children
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Treatment of TB
A long course of antibiotics (6 months)
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What does TB do in the alveoli? Explain the result of this
Forms nodules and eventually fills them, therefore decreasing the surface area for the alveoli to exchange gases. If it happens to lots of the alveoli, it can become hard to get O2 into the blood.
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What happens when TB forms nodules in lots of the alveoli?
It can become hard to get O2 into the blood
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Describe the experience of having the TB disease
It’s a slow, progressive disease - someone as it for a while before their health starts to deteriorate
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What did TB used to be spread through?
Infected milk
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How is milk treated to avoid it spreading TB?
Pasteurisation of milk is now used to kill the Tuberculosis bacteria
- heated to kill the bacteria
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TB
Tuberculosis
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List the different ways in which viruses affect cells
- cell lysis when they escape form cells to infect other cells/organisms (shedding)
- production of toxic substances
- cell transformation where they can trigger cells to become cancerous
-suppress the immune system
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Shedding
Cell lysis when viruses escape the cells to infect other cells/organisms
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How are certain cancers avoided by cell transformation where viruses trigger cells to become cancerous?
HPV injections help avoid cervical cancers
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Give an example of a viruses that suppresses the immune system
HIV affects T-helper cells
75
Describe the lytic cycle
1. Virus injects its genetic material into the cell. The virus can also get into the cell by endocytosis to release its genetic material
2. Viral genes contain viral DNA and these can be replicated to make new viral proteins inside the host cell
3. New viral cells break out of the host cell, causing the lysis of the host cell, which kills the host cell, so that the viral cells can now infect other cells
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Ways in which a virus particle can get into a host cell
-by the virus injecting its genetic material into the cell
-by endocytosis
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What can happen instead of just the lytic cycle?
The lysogenic cycle
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What happens during the lysogenic cycle?
DNA is incorporated into the cell and becomes part of the cell’s DNA but doesn’t cause the lytic cycle at first
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What does the DNA of the virus do during the lysogenic cycle?
Can hide in the DNA of the cell and is replicated as viral DNA
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In which cycle are there no symptoms and in which cycle are there symptoms?
No symptoms = lysogenic cycle
Symptoms = lytic cycle
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What can happen at some point during the lysogenic cycle?
The virus can switch to the lytic cycle and cause symptoms
82
Explain chicken pox in terms of the 2 cycles of viruses
The chicken pox is always in the person’s body as part of the lysogenic cycle. The lytic cycle either happens earlier on in the person’s life and causes chickenpox, or it can stay n the system for a long time and the lytic cycle occurs later on to cause shingles. These both have different symptoms, but it’s the same virus causing both.
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Can viruses be considered organisms?
It’s up for debate
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What is the only organism that humans have intentionally made extinct (outside specialist laboratories)?
Small pox
85
What is small pox?
A disease caused by a virus
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Which virus causes small pox?
*Variola major*
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What does the virus *Variola major* do?
Causes small pox
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Fatality rate of small pox v.s Covid
Small pox —> 30-60%
Covid —> 2%
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How infectious was small pox?
Just as infectious as Covid, if not more
90
What was a successful immunisation program for small pox based on?
Its low rate of antigenic variation/mutation and the highly immunogenic nature of its component antigens
91
Why was the vaccine for small pox highly effective?
Because the virus has a low rate of mutation
92
Explain why so many more vaccines needed to be generated for Covid compared to small pox
The small pox virus had a low rate of mutation
Covid, on the other hand, had lots of variants due to mutations in the virus’ genetic material, which caused a change in the protein coat of the virus so that vaccines no longer worked
The virus causing small pox was much more stable, so just one vaccine could be used
This means that the vaccine was highly effective
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Why do mutations mean that vaccines no longer work on viruses?
Mutations cause a change in the protein coat of the virus so vaccines no longer work
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Extra reasons why small pox was able to be made extinct
There was no animal reservoir
People were keen to be immunised because of the devastating effects of the disease (much more serious than chicken pox)
95
How long has it been since there was a case of smallpox?
Many decades (since 1979)
96
What form a protein on the outside of the small pox virus?
Surface tubules
97
What do surface tubules do for a small pox virus?
Form a protein on the outside of the virus
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Genetic material of a smallpox virus
DNA genome
99
Why do we still have some small pox virus particles in laboratories?
It’s important to keep some in order to make a vaccine if it reappears
100
Where is the nucleoprotein (RNA) of the influenza virus?
In the core of the virus
101
What is in the core of the influenza virus?
The nucleoprotein (RNA)
102
What type of virus is the influenza virus?
An RNA virus
103
Why is the influenza virus an RNA virus?
The genetic material of the virus is RNA
104
Is there more variation in the flu virus or the small pox virus? Why?
The influenza vis is an RNA virus
RNA mutates easier and more often than DNA
This means that there’s much more variation in the flu virus than the small pox virus
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What is the protein coat of the influenza virus?
The capsid
106
What is the capsid of the influenza virus surrounded by?
A lipid envelope
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What has the lipid envelope of the influenza virus derived from?
The host’s cell membrane
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What does a virus do when it breaks out of a host cell via exocytosis?
Brings some of the host cell’s membrane with it
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How does a virus break out of a host cell?
Via exocytosis
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What do we refer to viruses as and why?
Particles, not cells
They don’t have organelles, just a core with genetic material
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2 important spike proteins on the influenza envelope
Neuraminidase
Hemagglutinin
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What can both Neuraminidase and Hemagglutanin do for the influenza virus?
These can lock onto receptors in the host cell membrane and enable the virus to gain entry into the host cell
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What do the spikes on a particular influenza virus vary depending on?
The version of the flu virus
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Examples of versions of influenza virus + explain
H5N1
H1N1
H = Hemagglutinin
N = Neuraminidase
= referring to the protein spikes
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What is influenza caused by?
A virus
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How many sub-groups of the influenza virus are there?
3 main sub groups
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What is there within each main sub group of influenza virus?
Many different antigenic types
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Give examples of antigenic types of the influenza virus?
H5N1, H1N1
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What are H1N1 and H5N1 examples of?
Antigenic types of the influenza virus
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Antigenic types
The types within the 3 main subgroups of the virus that causes influenza (e.g - H5N1, H1N1)
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Where in the body does the influenza virus infect?
The upper respiratory tract
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Symptoms of the influenza virus being present
Sore throat
Coughing
Fever
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How do we know that someone isn’t suffering from the flu and it’s just a cold?
No fever (high temperature) = not the flu, just a cold
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What do we know if someone says they have the usual symptoms of a cold but also a fever (high temperature)?
They might have the flu
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How do sufferers spread flu?
By droplet infection
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What does prevention of the flu include?
Quarantine and hygiene
127
Why is influenza difficult to control?
Its mode of spread is difficult to control
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Affect of antibiotics on influenza
Ineffective
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Why do we use antibiotics on people with the flu if antibiotics are ineffective against infleunza?
They’re only used to treat the symptoms of secondary bacterial infection
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Explain how and why antibiotics are used to treat the symptoms of secondary bacterial infection (relating to the flu)
Antibiotics don’t affect viruses at all, so they’re not used for the actual flu. They’re used to treat secondary bacterial infection.
You’re more likely to get other symptoms from the flu due to the weakened immune system and those are what the antibiotics are used for
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Why are you more likely to get other symptoms when you have the flu?
Since you’ll have a weakened immune system
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What is currently being done to combat the flu?
Annul vaccination programmes are available
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Why are annual vaccination programmes against the flu not always effective?
Due to the number of types, together with the emergence of new types of flu
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What happens every year in terms of the flu?
Annual outbreaks
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What’s true about annual vaccination programmes for the flu and why?
They’re not always effective due to the number of types, together with the emergence of new types
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What is malaria caused by?
The parasite *Plasmodium spp*
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What does the parasite *Plasmodium spp.* cause?
Malaria
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What type of parasite is Plasmodium?
Protoctistan
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Is malaria bacterial or viral? Why?
No
It’s caused by a parasite
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Explain where malaria is present
It’s endemic in some sub-tropical regions (always present at a low level and rarely leads to big epidemics)
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When can malaria lead to big epidemics?
In wet seasons
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How come so many people are affected by malaria?
There are large populations in the areas where it’s endemic
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Why is malaria so bad?
It can kill
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What is malaria caused mainly by?
2 species, within which are many antigenic types
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Why is malaria hard to vaccinate against?
The disease is caused mainly by 2 species, within which a re many antigenic types
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What does it lead to due to there being many antigenic types of the 2 species that cause malaria?
It’s hard to vaccinate against
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Why can malaria be regarded as a pandemic?
It affects millions of people worldwide and kills more than any other infection, despite the years of research and drug development
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Which mosquitos are vectors of malaria?
Females
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What are female mosquitos to malaria and why?
Vectors, since they transmit the parasite to new victims
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Why are male mosquitos not vectors of malaria?
They feed on plant nectar, not blood
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What type of mosquitos feed on blood?
Pregnant females
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Why could the malaria parasite not exist without mosquitos?
It couldn’t be transmitted and part of its life cycle takes part in the mosquito
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Where do malarial parasites reproduce asexually in a human?
Liver
Red blood cells
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Describe the transmission of malaria
When a mosquito takes blood from an infected person, it takes in the sexually reproducing stage of Plasmodium called gametocytes. They produce zygotes high develop not an infective stage, called sporozoites. Sporozoites migrate from the mosquito’s gut to its salivary glands.
When the mosquito feeds on another human’s blood, it transmits the parasite - Pladmodium sporozoites in the mosquito’s saliva are infected into the human. They transfer to the liver and reproduce asexually in the liver cells to multiply and produce merozoites.
Merozoites are released into the blood and infect red blood cells, where they do more asexual reproduction to multiply in number.
The red blood cells burst and release more merozoites, which causes severe bouts of fever. The merozoites infect more red blood cells. This cycle repeats every few days and when the red blood cells burst, the fever recurs.
Some merozoites become gametocytes.
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Where do the parasites migrate to in a mosquito ?
The salivary glands
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When does someone experience severe bouts of fever with malaria?
When the parasite bursts out of red blood cells
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Where does the sexual stage of the life cycle of the malarial parasite occur?
Starts in the human red blood cell and is completed in the mosquito (eggs and sperm develop and undergo fertilisation and form a zygote in the mosquito)
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Why is malaria difficult to treat?
The parasite reproduces inside human cells (liver and red blood cells) where its able to hide from drugs and the immune system
Its evolved with us for millions of years and so its efficient at hiding from the immune system
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How come the malarial parasites able to hide from drugs and the immune system?
The parasite reproduced inside human cells (liver and red blood cells)
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When is the malarial parasite susceptible to drugs?
When it’s free in the blood plasma when its broken out of liver cells
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What is the malarial parasite susceptible to when it’s free in the blood plasma and has broken out of liver cells?
Drugs
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What does the prevention of malaria rely on and why?
Knowledge of the life cycle of both the vector and the parasite in order to exploit their weak points
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What gives us the opportunity to control the disease of malaria?
The fact that the parasite has 2 host organisms
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How can we control malaria based on the fact that the parasite has 2 host organisms?
By controlling the mosquitos (kill and stop from feeding on human blood)
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When do mosquitos feed on blood and why?
At night
They’re nocturnal
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Methods of protecting yourself from malaria
Insecticide treated nets and beds
Insect repellent
Clothing
Screening
Coils and creams
167
Give the anti larval methods of preventing malaria
Chemicals
Environmental (source reduction) e.g - species specific measures, filling, levelling and draining of breeding sites, oil on water surface
Biological - microbial insecticides, natural predators, eaten by introduced fish (mosquito larvae are aquatic)
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Why can fish be used to prevent the spread of malaria?
Mosquito larvae are aquatic so if we get fish that eat these it will cut down on the amount of vectors to spread the disease
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Why does putting oil on water surfaces help prevent the spread of malaria?
Mosquito larvae depend on reaching air - they have breathing tubes which break through the water tension and with oil on the surfaces, these tubes get blocked, so they can’t respire
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Give the anti adult methods of preventing malaria
Genetic control —> cytoplasmic incompatibility, chomosomal translocations, sterile male techniques (when a female breeds with the male, the eggs don’t develop. Female mosquitos only feed on blood when their eggs are developing, so they’ll stop doing this)
Bacterial infections
Insecticides
Residual sprays (long term effects) —> DDT
171
Why do sterile male techniques of mosquitos help prevent the spread of malaria?
When a female breeds with the male the eggs don’t develop. Female mosquitos only feed on blood when their eggs are developing so they’ll stop doing this
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When is the only time female mosquitos feed on blood?
When their eggs are developing
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How do we sterilise male mosquitos?
Using ionising radiation
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How many genuses of mosquito spread malaria?
Only 1
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Give the life cycle of the *Anopheles mosquito*
Adult (that feeds on blood) lays eggs on the water
Eggs hatch to form larvae
Large undergoes metamorphosis
Breaks out as an adult
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What do all of the control measures of malaria have?
Advantages and disadvantages
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Disadvantage of using oil on the surface of water to control malaria
Affects other species and causes contamination
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Disadvantage of using fish that feed on malarial larvae to control malaria
Introducing a non-native fish can effect the ecosystem
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What is drug treatment against malaria used for?
It’s mainly used to reduce the chances of infection
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Explain why drug treatment against malaria is mainly used to reduce the chances of infection
The parasite is most vulnerable when first infected into the human host and is free in the plasma. This is when it can be killed by drugs and so taking them before being infected is effective.
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When is the malarial parasite most vulnerable to drug treatment?
When first injected into the human host and is free in the plasma
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When can the malarial parasite be killed by drugs?
When its first been injected into the human cost and is free in the plasma
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Why have vaccines been proved to be difficult to develop against malaria?
The malarial parasite mutates
There are different antigenic types
Different species of plasmodium
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What has been difficult to do since the malarial parasite mutates and there are different antigenic types and different species of plasmodium?
Develop Vaccines
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What are antibodies?
Proteins produced by the body
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When are anti bodies effective against the malarial parasite? What does this lead to
When outside body cells
Limiting the target stages for a vaccine
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Pathogenic
An organism that causes damage to its host
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Infectious
A disease that may be passed on or transmitted from one individual to another
189
Carrier
A person who shows no symptoms when infected by a disease organism but can pass the disease on to another individual
190
Disease reservoir
Where a pathogen is normally found. This may be in humans or another animal and may be a source of infection.
191
Endemic
A disease which is always present at low levels in an area
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Epidemic
Where there is a significant increase in the usual number of cases of a disease often associated with a rapid spread
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Pandemic
An epidermic occurring worldwide, or over a very wide area, crossing international boundaries and usually affecting a large number of people
194
Vaccine
Use non-pathogenic forms, products or antigens of microorganisms to stimulate an immune response which confers protection against subsequent infection
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Antibiotics
Substances produced by microorganism which affect the growth of other microorganisms
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Antibiotic resistance
Where a microorganism which should be affected by an antibiotic is no longer susceptible to it
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Vector
A living organism which transfers a disease from one individual to another
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Toxin
A chemical produced by a microorganism which causes damage to its host
199
Antigenic types
Organisms with the same or very similar antigens on the surface. Such types are sub groups or strains of a microbial species which may be used to trace infections. They are usually identified by using antibodies from serum
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What are sub groups or strains of a microbial species which may be used to trace infections?
Antigenic types
201
How are antigenic types usually identified?
By using antibodies from serum
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Antibiotic definition
Substances produced by microorganisms which inhibit the growth of or kill bacteria
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What are antibiotics also known as?
Anti microbial agents
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What are antibiotics secreted by?
They’re chemicals secreted by fungi or other bacteria
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Explain why antibiotics are secreted by fungi or other bacteria
In order to decrease competition for food
In their natural environment, they would mix with organisms competing for the same food source
When these chemicals are released, it gives them a selective advantage
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2 categories of antibiotic
Bactericidal
Bacteriostatic
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What do bactericidal bacteria do?
Kill bacteria
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What do bacteriostatic bacteria do?
Inhibit bacteria from multiplying
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Why is it useful that bacteriostatic antibiotics inhibit bacteria from multiplying?
By stopping bacteria from multiplying, it is the immune system a better chance to kill the infection
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What 2 things can antibiotics be?
Broad or narrow spectrum
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Broad spectrum antibiotics
Affect many species of bacteria - gram positive and gram negative
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Narrow spectrum antibiotics
Much more selective e.g- Penicillin G only kills gram positive bacteria
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Example of a narrow spectrum antibiotic + explain
Penicillin - only kills gram +ive bacteria
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Disadvantage of broad spectrum antibiotics
Could kill good bacteria in the bodies microflora ,which may be harmful in the long term
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When should broad spectrum antibiotics be used?
If it can’t quickly be decided which bacteria is responsible for an infection but based on the symptoms, it’s definitely a bacterial infection, broad spectrum antibiotics should be used
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What’s better - broad or narrow spectrum antibiotics and why?
Narrow spectrum
They target the group the pathogen belongs to and don’t kill the bodies natural flora
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2 types of antibiotic to learn about
Penicillin
Tetracycline
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Explain exactly how Penicillin works
Penicillin affects/prevents the formation of cross linkages in the peptidoglycan cell wall during the growth and division of bacterial cells
It does this by binding to and inhibiting the enzyme responsible for the formation of cross links between molecules of peptidoglycan
The cell wall is weakened so when osmotic changes occur, the cells lyse
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What does penicillin prevent the formation of?
Cross linkages in the peptidoglycan cell wall
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Explain why cells lyse when the cell wall of bacteria is weakened by Penicillin
The water potential inside the bacterial cell is low, whereas outside, the water potential is high (the cytoplasm would be the natural environment of the cell)
This hydrostatic pressure on the cell wall would usually resist its expansion, however upon weakening the cell wall, the pressure can cause lysis
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Natural environment of a bacterial cell
Cytoplasm
222
2 ways to describe Penicillin as an antibiotic
Narrow spectrum
Bactericidal
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Explain why penicillin is a narrow spectrum antibiotic
It’s not effective against gram negative bacteria since they have a lipopolysaccharide layer around the thin peptidoglycan layer, whereas it is more effective against gram positive bacteria with its lack of lipopolysaccharide layer around the peptidoglycan layer
224
What is Penicillin effective against and what isn’t it effective against? Why?
Not effective against gram negative bacteria -> they have a lipopolysaccharide layer
Is effective against gram positive —> no lipopolysaccharide layer
225
Would penicillin work against cholera? Why?
No
Cholera is a gram negative bacteria (lipopolysaccharide layer)
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Why aren’t eukaryotic (i.e - human cells) affected by penicillin?
Since eukaryotic cells don’t have cell walls, so of course they wouldn’t be affected by a chemical that effects cell wall formation
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2 ways of describing the tetracycline antibiotic
Bacteriostatic
Broad spectrum
228
Explain how Tetracycline acts as an antibiotic
It affects protein synthesis, a metabolic process common to all bacteria, and is effective against a broader range of bacteria
It acts by acting as a competitive inhibitor of the second anticodon-binding site on the 30s subunit of bacterial ribosomes and prevents the binding of a tRNA molecule to its complementary codon on mRNA. This means the amino acid isn’t added to the polypeptide and so translation has been inhibited in protein synthesis
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Why is Tetracycline a broad spectrum antibiotic?
It acts on the bacterial ribosome, so it stops protein synthesis in *all* bacteria
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Why is Tetracycline a bacteriostatic antibiotic?
Since the bacterial cell can still survive, but it can’t grow if it can’t make proteins
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Would Tetracycline work against chlorella why?
Yes
It affects protein synthesis - a metabolic process common to all bacteria
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Why does Tetracycline not affect human cells?
It doesn’t affect translation in human cells since our ribosomes are different to bacterial ribosomes (80s = bigger)
233
What has led to the spread of antibiotic resistant strains of bacteria?
The overuse of antibiotics
234
What has the overuse of antibiotics led to?
The spread of antibiotic resistant strains of bacteria
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Fields in which antibiotics can be used
Medicine, agriculture
236
What is the issue that antibiotics are used in agriculture?
Resistance can be passed on between species on plasmids
237
How is antibiotic resistance passed on between species?
On plasmids
238
Explain how antibiotic resistance comes about
Bacteria divide rapidly under optimum conditions and have a high mutation rate
Naturally occurring mutations that confer resistance to antibiotics have given these bacteria a selective advantage in the presence of antibiotics within a population, which pass this on
Overuse of antibiotics has resulted in the accidental selection of bacterial strains that are completely unaffected by antibiotics
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How has antibiotic resistance basically occurred?
natural selection due to a selective pressure that humans made themselves through the use of antibiotics
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Antibiotic resistant bacteria in the absence of antibiotics and when they cause an infection
In the absence of antibiotics, they no longer have an advantage over non-mutated forms
If they cause an infection, they’re becoming increasingly difficult to control
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What do bacteria do under optimal conditions?
Divide rapidly and have a high mutation rate
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What confers resistance to antibiotics to bacteria?
Naturally occurring mutations
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Give an example of an antibiotic resistant bacteria
MRSA
It’s resistance to all but 2 antibiotics that have been discovered
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What are the ways in which we can cut down on antibiotic resistant bacteria?
Look for new types of antibiotics
Use new ways of controlling bacterial infections (e.g - Bacteriophage virus)
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Advantage of using Bacteriophage viruses instead of antibiotics
They infect bacteria with the advantage of being specific to a particular species of bacterium and only killing that type = no effect on the natural body bacteria
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What are all of the natural barriers that we have to reduce the risk of infection?
Skin
Skin flora
Blood clotting
Inflammation
Phatgotytosis
Ciliated mucous membranes
Lysozyme
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What is needed to maintain skin as a tough barrier against infection?
Vitamin C is essential in our diet to maintain strong connective tissue
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Why is vitamin C important in our diets?
It maintains strong connective tissue
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What happens when we don’t have enough vitamin C?
Vitamin C deficiency
Weakened connective tissue = more likely to get infections
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Skin flora
Bacteria that grow on the skin surface
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Bacteria that grow on the skin surface
Skin flora
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Why is the skin flora useful?
It offers protection by competing with pathogenic bacteria, and unlike these bacteria, the flora is not easily removed by washing
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Why is blood clotting good?
To seal wounds
To stop bleeding
To stop any pathogens from getting into the cut skin
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Why does inflammation occur and why is it useful?
When you get an injury, the area becomes swollen due to increased blood flow, and this prevents any breaks in the barrier from spreading/localises breaks in the barrier
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What is phagocytosis done by and why?
White blood cells
To destroy invading microbes
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How do white blood cells destroy invading microbes?
Via phagocytosis
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Where can ciliated mucous membranes be found?
In trachea and bronchi
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What do ciliated mucous membranes in trachea and bronchi do?
Trap microbes in inhaled air
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Where is lysozyme found?
Tears, saliva and stomach acid
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What does lysozyme do?
Kills bacteria (digest bacterial cell walls, not human cells)
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Why are all of the natural barriers to infection non-specific?
They stop *any* bacteria from entering the body
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Describe all of the natural barriers to infection
Natural, non-specific, first-line barriers
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Why is the adaptive immune system better than just the natural barriers to infection?
It’s a much more targeted response against invading pathogens
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What does the adaptive immune system involve?
It’s specific to the pathogen and involves recognising antigens for being “foreign” to the body
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What is the adaptive immune response specific to?
The pathogen
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2 strands of action of the immune system
The humoral response
The cell mediated response
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What are the humoral response and the cell mediated response?
The 2 strands of action of the immune system
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What’s the most important part of the adaptive immune system?
Antibodies
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What are antibodies?
Quaternary protein molecules known as globulins
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Quaternary protein molecules
2+ polypeptide chains joined together
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Shape of antibodies
Characteristic 3D globular structure
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What do antibodies consist of?
4 polypeptides
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Describe the polypeptides that make up antibodies
Two heavy chains and two light chains
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What are the polypeptide chains of antibodies joined by?
Disulphide bonds
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Describe the 3D shape of the binding site of an antigen
It’s specific and varies and is complementary to the shape of a specific antigen molecule
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Why are the binding sites of antibodies specific?
They only bind to 1 particular antigen
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What are antibody molecules synthesised by?
B lymphocytes
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What do B lymphocytes synthesise?
Antibody molecules
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What are the 2 regions of an antibody?
Variable region and constant region
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Which part of an antibody varies in structure and which is the same in all antibodies?
Variable region varies in structure
Constant region is the same in all antibodies
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Antigen
Any molecule which has a specific shape that antibodies can recognise
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What are antigens usually and why?
Proteins
These have a specific 3D shape
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What could the protein form of antigens be?
The surface proteins of virus particles or bacterial cells or protistant parasites etc
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What happens when an antigen changes in terms of antibodies?
When an antigen changes (i.e - its surface proteins change), the antibody will no longer bind to it since the antigen binding site is no longer complementary
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What needs to be made when an antigen changes?
New antibodies
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Why was Covid so hard to treat (in terms of antigen and antibodies)?
The virus kept mutating (the antigens changed) so antibodies would no longer be able to bind to them since the antibody binding sites were no longer complementary
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Why is the adaptive immune system adaptive?
Since it learns from encountering new antigens
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Explain how the adaptive immune system works
It recognises foreign antigens and allows you to develop immunity for next time, which is why there are some diseases you can only get once.
The adaptive immune system learns antigens so that the body can recognise them next time and destroy the, for example, virus before it causes any symptoms
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Why are there some diseases you can only get once?
The adaptive immune system learns the antigens so that the body can recognise them next time and destroy them before they cause any symptoms
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What does the adaptive immune system do when it recognises foreign antigens?
It allows you to develop immunity for next time
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What type of lymphocytes does the humoral response involve?
B lymphocytes
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What are B lymphocytes involved in?
The Humoral response
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Where do B lymphocytes originate from?
Stem cells in the bone marrow, and mature in the spleen and lymph nodes
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What does each B lymphocyte have?
Receptor for the detection of its specific antigen
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What does the activation of B lymphocytes do?
Stimulates the proliferation (fast increase in numbers) of antibody producing cells, plasma cells and memory cells
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The activation of what stimulates the proliferation of antibody producing cells, plasma cells and memory cells?
B lymphocytes
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What do memory cells do?
They remain in the circulation ready to divide if the same antigen is encountered again
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What type of proteins are antibodies?
Globulins
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What are antibodies specific to?
The antigen with which they bind to form an antigen-antibody complex
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What forms when an antigen and an antibody bind to each other?
An antigen-antibody complex
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What shape do antibody molecules have?
Y shapes
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How many polypeptide chains are antibodies formed from?
4
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How many bonding sites do antibodies have?
2
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What happens when an antigen-antibody complex forms?
The antigen-antibody complex renders the antigen inactive in some way, such as through agglutination, which increases the rate of engulfment by phagocytes
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Phagocytes
Cells that swallow the pathogen
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Example of how an antigen-antibody complex renders the antigen inactive in some way
Through agglutination
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What does agglutination increase the rate of?
Engulfment by phagocytes
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Agglutination meaning
Sticking together
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Explain how agglutination occurs
The antigens have 2 binding sites = bind to other cells = form clumps = agglutination
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Why is agglutination useful?
It makes it easier for phagocytes to engulf clumps of cells via phagocytosis
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Explain the Humoral response of the adaptive immune system
There are lots of different types of B lymphocytes in the body, each with different receptors on their surface. One of these will match the antigen.
Once the antigen has bound to the correct B lymphocyte, the cell is activated
This means that it’s triggered to proliferate and divide by mitosis
Some of the B lymphocytes become plasma cells, which secrete antibodies into circulation
Some become memory cells, which stay in circulation after the infection has passed
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What’s different about the different B lymphocytes in the body?
They have different receptors on their surface - one of these will match the antigen
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When is a B lymphocyte activated?
Once the antigen has bound to the correct B lymphocyte
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What happens to a B lymphocyte once it’s activated?
It’s triggered to proliferate and divide by mitosis
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What are the different types of cells that B lymphocytes become during the humoral response?
Plasma cells
Memory cells
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What do plasma cells formed from B lymphocytes in the humoral response of the adaptive immune system do?
They secrete antibodies into circulation
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What do memory cells produced from B lymphocytes in the humoral response of the adaptive immune system?
Stay in circulation after the infection has passed
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When does the cell mediated response of the adaptive immune system occur?
In parallel with the humoral response
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What type of lymphocytes does the cell mediated response involve?
T lymphocytes
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What are T lymphocytes involved in?
The cell mediated response of the adaptive immune system
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Where do T lymphocytes originate from?
Originate from stem cells in the bone marrow, but are activated in the thymus gland
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Why are T lymphocytes called this?
Since they’re activated in the *T*hymus gland
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What causes the proliferation of T lymphocytes?
Detection of the corresponding specific antigen
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What does the detection of the corresponding specific antigen cause for T lymphocytes?
The proliferation of T lymphocytes
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Subpopulations of T cells after they’ve differentiated during proliferation
Effector cells (T killer or cytotoxic T lymphocytes)
Helper T cells
Memory cells
Regulator T cells
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What do cell-mediated defenses include?
The activation of phagocytes
Antigen-specific killer/cytotoxic T lymphocytes
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What does the activation of B cells involve the release of?
Various chemicals - cytokines - in response to an antigen
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Cytokinesis
chemicals released in response to an antigen after the activation of B cells
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What are involved as well as T lymphocytes in the cell-mediated response of the adaptive immune system?
Macrophages
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What do macrophages do?
Swallow anything foreign and they take the antigen from the pathogen and display them on the surface membrane of the cell
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What do T cells do after a macrophage has displayed an antigen on the surface membrane of the cell?
A T cell with a receptor binds to the antigens on the macrophage surface membrane, and this activates the helper T cell, causing it to proliferate and differentiate into the 4 types of T cell
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What type of T cell is activated to proliferate and differentiate into the 4 types of T cell?
T helper cells
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What do killer T cells do?
Destroy the pathogen by causing the lysis of the pathogen
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List all of the things that helper T cells do
Cooperate with B lymphocytes to initiate an antibody response
Activate other T cells and B cells to proliferate and produce antibodies
The helper T cells are what produce cytokines which stimulate killer T cells and B cells
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What produces cytokines?
Helper T cells
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What do cytokines do?
Stimulate killer T cells and B cells
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What do memory T cells do?
Remain in the plasma and lymph nodes in circulation to respond rapidly if the same type of pathogen invades again
They remain dormant until the host is next exposed to the antigens
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Where do T memory cells remain?
In the plasma and lymph nodes in circulation
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What do regulator T cells do?
Slow down and stop the immune reaction after about 1 week
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If a virus infects body cells, the T cells carrying the antibody for that virus multiply rapidly to form what?
A clone
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What a killer, helper, memory and regulator T cells all examples of?
Clones, with different functions
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When does the primary immune response occur?
When we encounter an antibody for the first time
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Explain the primary immune response
Following first exposure to a foreign antigen there is a latent period during which antigen presenting cells (including macrophages) carry out phagocytosis and incorporate foreign antigen into their cell membranes
T helper cells detect these antigens and secrete cytokines which stimulate B cells and macrophages
B cells are activated and undergo clonal expansion (proliferation by mitosis) - some then differentiate to become antibody secreting plasma cells with short lives ad others to become long lived memory cells that retain the ability to undergo mitosis
A low level of antibody is secreted by B plasma cells for about 3 weeks. This clears the infection and symptoms disappear.
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Compare the lives of plasma cells and memory cells
Plasma cells (antibody secreting) = short lives
Memory cells = long lives
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When does the secondary immune response occur?
Could happen years after the primary immune response
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Explain the secondary immune response
Following re-exposure to the same antigen, there is a very short latent period due to the presence of memory cells
Only a very small amount of antigen is required to stimulate rapid production of plasma cells
Antibody levels increase to between 10 and 100x greater than the initial response and in a very short time (faster + stronger response)
Antibody levels stay high for longer and no symptoms develop - the pathogen is destroyed before symptoms appear
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Which period of the secondary immune response is much shorter than the primary immune response and why?
Latent period
Due to the presence of memory cells
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How can immunity be acquired?
Whether humoral or cell mediated, can be acquired either actively or passively
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Active immunity
Where the individual produces antibodies
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Immunity where an individual produces antibodies
Active immunity
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2 possibles types of active immunity + explain
Natural if it follows natural infection
Artificial if it follows vaccination (e.g - against Rubella in MMR vaccine)
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Problem with Rubella
Harms a developing foetus in a pregnant woman
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Which type of immunity provides long lasting protection and why?
Active immunity
Due to the production of antigen-specific memory cells
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Passive immunity
Where the individual receives antibodies produced by another individual
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Where the individual received antibodies produced by another individual
Passive immunity
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When can passive immunity be natural?
When antibodies are transferred to the foetus via the placenta, or to the body in breast milk
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Why is it important that antibodies are circling in the blood of a foetus when born?
Since the adaptive immune system of a newborn isn’t fully developed
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When is passive immunity artificial?
When pre-synthesised antibody is injected into an individual (e.g - tetanus antitoxin)
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What type of immunity only provides short lived protection and why?
Because the antibodies are recognised as non-self and are destroyed and no memory cells are produced
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What is vaccination an example of?
Artificial active immunity
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Explain how vaccinations work
They promote a primary immune response without causing the disease. Memory cells are produced and enter circulation so that when the individual is exposed to the disease, a secondary response occurs so symptoms do not develop since it’s faster and destroys the pathogens before symptoms develop.
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3 main differences between a primary and secondary immune response
No latent period in the secondary immune response - antibodies are produced immediately
The secondary immune response is faster than primary
A higher level of antibodies is produced which remain at a higher level for longer than in the primary immune response
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What must vaccines not do and what should they do?
Must not cause the disease
Should provide a strong immune response
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How should vaccinations give antigens?
Without giving the live pathogen
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What are the main types of vaccine?
1. Killed pathogen
2. Attenuated
3. Toxoid
4. Subunit
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Explain and give examples of killed pathogen vaccines
Some vaccines contain microorganisms which have been killed with chemicals or heat
E.g - vaccines against flu, cholera, polio, bubonic plague, hepatitis A
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Explain and give examples of attenuated vaccines
Contain live, attenuated (weakened) microorganisms. These are live microorganisms that have been cultivated under conditions that make them non-pathogenic, or are closely-related, non-pathogenic microorganisms, to produce a broad immune response. The pathogen will be too weak to multiply and cause the disease.
Examples: measles, mumps, rubella, tuberculosis, yellow fever
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Explain and give examples of toxoid vaccinations
These are inactivated toxic compounds in cases where these compounds, rather than the microorganism itself, cause illness
Examples : tetanus and diphtheria
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Explain and give examples of subunit vaccinations
Specific antigens or sub-units of a microorganism (especially viruses) can create an immune response
Examples: hepatitis B virus (composed of only the surface proteins of the virus)
Virus-like particle (VLP) vaccine against HPV that is composed of a viral major capsid protein
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What is artificial immunity?
In an emergency, antibodies can be enacted to provide rapid protection against a pathogen (e.g - in the case of rabies)
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What does artificial immunity allow time for?
Allows time for the person’s immune system to develop an active immune response
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What are injections of antibodies also used for apart from in emergencies?
With people who do not develop a strong immune response to vaccination or who have a weakened immune system
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What must the antigens used in a vaccine be?
Highly immunogenic and stimulate a protective immune response that is specific to the pathogen or antigen
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Why are different types and programmes of vaccination used?
To increase the chance of. Person developing protective, long-lasting immunity (e.g - booster vaccines which stimulate more memory cells to be produced)
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What’s the purpose of booster vaccines?
They stimulate more memory cells to be produced
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What type of pathogens are more likely to be protected by a single round of immunisations ? Give an empale
Pathogens that exhibit no or low levels of antigenic variation/mutation
e.g - rubella
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What type of pathogens are less likely to be protected by a single round of immunisations? Give an example
An organism that has many antigenic types and mutates frequently (e.g - influenza)
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What does protection against pathogens with many antigenic types that mutates frequently require?
Repeated immunisation against the most common antigens (and even then its not 100% effective)
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Active immunity v.s passive immunity
Active immunity = long lasting, produces memory cells
Passive immunity = short term, no memory cels and foreign antibodies eventually destroyed
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Artificial active immunity
Antibodies produced following a vaccination - B, T and memory cells are formed
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Artificial passive immunity
Foreign antibodies are injected
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Active natural immunity
Antibodies produced following an infection - B, T and memory cells are formed
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Cells formed for active immunity
B, T and memory cells
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Passive natural immunity
Mother’s antibodies passed on to foetus through the placenta and milk
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Example of active immunity
Rubella
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Example of passive immunity
Tetanus
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Ethical issues connected to vaccination programmes
The cost and effectiveness of the vaccines (it’s expensive to immunise a lot of people = how many will actually be saved?)
The protection of individuals and the community and whether vaccination should be compulsory (e.g - for health care workers) lots of people refuse vaccinations and this leads to a higher risk of the disease spreading through the population since some people can’t be vaccinated for health reasons, and these people would be the most vulnerable to disease too
The rights of individuals to refuse vaccinations; this may particularly apply to parents choosing not to vaccinate their children
Real and perceived side effects
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What’s a better option than using a “molecular patch” to treat dystophin and why?
Use a drug to remove mutated exons dystrophin gene since it’s more permanent and change is present after the cell replicates
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Why are antibodies not secreted immediately with the primary immune response?
As we have a latent period - time is needed to produce and secrete antibodies
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What secrete antibodies during the secondary immune response?
Memory cells
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How would an agglutination test be able to distinguish between two strains of bacteria?
Antibodies are specific to an antigen
Different strains would have different antigens
No agglutination = different strain
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How do we confirm the source of an outbreak?
Compare distribution of known strains of the bacteria to locate the possible source of
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Why are antibiotics alone not a cure for cholera?
Will pass through the gut before all bacteria killed
V. Cholerae is gram negative = some antibiotics are not effective since they’re narrow spectrum
Kill bacteria but toxin remains
+ antibiotic resistance
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What do second doses of vaccination do?
Act as booster vaccinations to increase antibody levels and increase memory cells
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Why would tetracycline not affect viruses?
It’s an antibiotic that affects protein synthesis, a metabolic process
Viruses have no metabolism
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Do viruses have metabolism?
No
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What’s a key word to use when describing how B lymphocytes become plasma cells and memory cells?
Differentiate
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How do viruses kill their host cells?
Suppress the immune system
Cell transformation - trigger cells to become cancerous
Cell lysis when they escape from the cells to infect other cells/organisms
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Why do virus particles enter host cells?
Need host cell for metabolic processes
Has no organelles
Uses cell metabolic pathways for reproduction
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Features of a successful vaccine
Trigger an immune response
No harm caused
