Communicable Diseases, Disease Prevention And The Immune System Flashcards
1
Q
What are pathogens?
A
They are microorganisms that cause diseases
2
Q
What are communicable diseases?
A
They are diseases that can be transferred from one organism to another
3
Q
What are Vectors?
A
They are substances that carry the pathogens from one organism to another and are involved in the spread of plant and animal diseases
4
Q
Types of pathogens
A
Bacteria, virus, fungi and protoctista
5
Q
What are the two ways bacteria can be classified?
A
- Based on their shape- they can either be rod shaped, spherical, spiral, corkscrew or comma shaped
- Based on their cell wall- bacterial cell walls have different structures and react differently in a process called Gram staining
6
Q
How do viruses cause diseases?
A
They invade living cells where they release their genetic material and insert it into the host DNA, making more viruses which burst out of the cell, killing it and spreading to infect other cells
7
Q
How are protoctista diseases spread?
A
They use vectors to transfer them to their host or they may enter the blue through polluted water
8
Q
What type of feeders are fungi?
A
Many fungi are saprophytic feeders but some are parasitic feeders which means they feed on living plants and animals and these are the pathogenic fungi that causes communicable diseases
9
Q
What do fungi produce when they reproduce?
A
They produce millions of tiny spores which can spread huge distances so they can spread very quickly and widely through crop plants
10
Q
What are the two modes of pathogen action?
A
- Damaging the host tissue directly and
- Producing toxins which damage the host tissues
11
Q
What pathogens damage the host tissues directly?
A
• Viruses take over by releasing their genetic material into the host cell and insert it into the host DNA. The virus then uses the host cell to make new viruses which then burst out of the cell, destroying it and then spread to infect other cells
• Protoctista simply digest and use the cell contents as they reproduce
12
Q
What pathogens produce toxins which damage the host tissues?
A
• Bacteria produce toxins that poison or damage the host cell causing diseases. Some bacteria produce toxins which break down the host cell membranes, inactive or damage enzymes and some interfere with the host cell genetic material so the cell cannot divide
13
Q
What happens when plant gets diseases?
A
They threaten people because when crop plants fail, people suffer. They may starve, economies may struggle and jobs are lost. Plant diseases also threatenes ecosystem
14
Q
What pathogens cause ring rot?
A
Ring rot is a bacterial disease which affects the field of potatoes so it cannot be used to grow potatoes for at least two years. There’s no cure
15
Q
What type of pathogen causes TMV?
A
TMV is a viral disease that discolours the leaves of tobacco or tomato plants. This prevents the plant from photosynthesising, stunting growth and reducing the yield of the crops
16
Q
What pathogen causes late blight?
A
It is caused by a Protoctista pathogen. The hyphae penetrates host cells destroying leaves causing damage to crops. It affects tomatoes and potatoes
17
Q
What pathogen causes black sigatoka?
A
It is caused by a fungus and it affects banana plants by attacking and destroying the leaves. The hyphae penetrates and digest the cells, turning the leaves black
18
Q
What type of pathogen causes tuberculosis (in animals)?
A
It is caused by a bacterial pathogen. It damages and destroys lung tissues and suppresses the immune system so the affected person is prone to getting infected by other diseases.
19
Q
How can tuberculosis be cured?
A
It is cured by antibiotics and preventable by improving living standards and vaccination
20
Q
What type of pathogen causes HIV/AIDS( in humans)?
A
It is caused by HIV which targets T helper cells in the immune system. It gradually destroys the immune system so affected people are prone to other infections
21
Q
What type of pathogen causes influenza (in animals)?
A
It is caused by a viral infection. It kills the ciliated epithelium cells leaving the airway open to secondary infections
22
Q
What type of pathogen causes malaria?
A
It is caused by plasmodium and is spread by a mosquito which acts as a vector
23
Q
What type of pathogen causes Athlete’s foot (in humans)?
A
It is caused by a fungus and it grows and digests the warm, moist skin between the toes.
24
Q
What is the cure for Athlete’s foot?
A
Use antifungal cream
25
How does HIV work?
It contains the enzyme reverse transcriptase which transcribes the RNA to a single strand of DNA in the host cell. The viral DNA then interacts with the host's genetic material and so more viral proteins are made.
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How is HIV spread?
It is passed from one person to another through bodily fluids, unprotected sex, shared needles and uncontaminated blood products. Females that have undergone FGM are more likely to have HIV
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Is there a cure for HIV?
There is no cure nor vaccine, but **anti-retroviral** drugs slow the progress of the disease
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What are the two main types of disease transmission?
Direct and indirect transmission
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What is direct transmission?
This is when the pathogen is transferred directly from one organism to another.
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Methods of direct transmission
1. By direct contact: kissing, contact with any bodily fluids from the infected person, direct skin-to-skin contact
2. Ingestion- taking in contaminated food or drink, or transferring pathogens from the hands to the mouth
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What is an indirect transmission?
It is the spread of pathogens from one organism to another through another medium
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Ways of indirect transmission in humans
1. Vectors- they transmit the communicable pathogen from the host to another organism
2. Fomites - inanimate objects such as beddings, socks, or cosmetic can transfer pathogen
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Factors increasing the likelihood of transmission in animals
1. Overcrowding
2. Poor nutrition
3. Poor disposal of waste providing breeding sites for vectors
4. Climate change
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Methods of direct transmission between plants
It involves direct contact of a healthy plant with any part of a diseased plant
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Methods of indirect transmission in plants
1. Vectors eg wind, water, humans, animals
2. Soil contamination
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Factors affecting the transmission of communicable diseases in plants
1. Overcrowding
2. Less resistance to the pathogen
3. Climate change
37
Suggest different approaches to control the spread of malaria (5 marks)
Treating people to reduce the pool of infection using medicines against disease(1); destroying mosquitoes that spread the disease (insecticide sprays on water and homes) (1); preventing mosquitoes from breeding (1) by draining swamps(1); removing waste filled with water (1); preventing mosquitoes reaching people by using mosquito nets over beds (1)
38
Describe how a plant response to a pathogen is triggered (3 marks)
Receptors on the plant cell wall respond to molecules from the pathogen(1) or chemicals released when the plant cell wall is being attacked(1). This stimulates the release of cell signalling molecules which switch on the genes in the nucleus, triggering cellular responses (1) such as sending alarm signals to other unaffected cells to trigger their defences, physically strengthening the cell wall or producing defensive chemicals
39
What are the physical defenses that plants carry out when they are attacked?
When they are attacked, they produce high levels of callose which is a polysaccharide involved in the strengthening of the cell wall and preventing the penetration of pathogens. Lignin is also added, making the mechanical barrier to invasion even thicker and stronger
40
What are the chemical defences plants carry out?
They release powerful chemicals that either repel the insect vectors or kill the invading pathogens.
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Examples of the chemical produced by plants
1. Insecticides
2. Insect repellents
3. General toxins
4. Antifungal compounds
5. Antibacterial compound eh antibiotics
42
What are the two lines of defenses mammals have against pathogens?
1. Non-specific defences and
2. Specific immune responses
43
Feature of the non-specific defences
1. It defends all pathogens in the same way
2. It is rapidly activated and it always present
44
What are the non-specific defences in mammals?
1. Skin
2. Expulsive reflexes eg coughing/sneezing which expels pathogens from gas exchange system. Vomiting and diarrhoea which expel pathogens from digestive system
3. Mucous membranes
4. Inflammatory response
5. Blood clotting and wound repair
45
Features of the skin that prevent pathogens from entering
1. It has a layer of dead cells which makes the skin difficult for pathogens to penetrate
2. It is covered in an oily substance called sebum which inhibits the growth of pathogens
3. Healthy skin also has healthy microorganisms which outcompete the pathogen for resources and space on the body surface
46
Describe the inflammatory response
Mast cells are activated in damaged tissues and release histamine and cytokines(1). Histamine causes vasodilation which increases the blood supply to the affected area causing it to be red and hot(1). This increased temperature prevents the pathogens from reproducing. Histamine causes the blood vessels to become leaky so blood plasma is forced out as tissue fluid which causes swelling (oedema) and pain(1)
Cytokines attract phagocytes to the site and dispose of the pathogen by phagocytosis
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What are phagocytes?
They are specialised WBC that engulf and destroy pathogens
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Types of phagocytes
Neutrophils- only involved in non-specific defences
Macrophages- they are involved in both the non-specific defences and the specific immune system
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Stages of phagocytosis- involving neutrophils
1. Pathogens release chemicals which attract phagocytes
2. Opsonins are chemicals that bind to the pathogen and "tag" them making them more easily recognised by phagocytes
3. Phagocytes have receptors on their cell surface membrane that bind to the opsonins and the phagocyte engulfs the pathogen forming a phagosomes
4. Lysosomes move towards and combine with the phagosome forming phagolysosomes
5. The lysosomal enzymes break down and destroy the pathogen
50
Stages of phagocytosis involving macrophages
1. When the macrophage has digested the pathogen, antigens on the surface membrane of the pathogen combine with glycoproteins in the cytoplasm called the major histocompatibility complex (MHC) forming an MHC- antigen complex.
2. The MHC-antigen complex then moves the antigen to the macrophages cell surface membrane becoming an antigen-presenting cell (APC)
51
What is the role of cytokines?
It acts as cell-signalling molecules, informing other phagocytes that the body is under attack and stimulates them to move to the site of infection or inflammation. They can also increase the body temperature and stimulate the specific immune system
52
What is the general structure of an antibody?
1. They are Y-shaped immunoglobulins which bind to a specific antigen on the pathogen that has triggered an immune response
2. They are made up of two identical long polypeptide chains called the heavy chains and two much shorter identical chains called the light chains. The chains are held together by disulphide bridges
3. The antibody has an antigen binding site which is complementary to the structure of the antigen. This makes the antibodies highly specific for the antigen they bind to.
4. The hinge region of the antibody provides the molecule with flexibility allowing the distance between the two antigen binding sites to vary
53
Function of antibodies
1. They act as agglutinins causing the pathogen carrying antigen-antibody complexes to stick together which prevents them from spreading through the body and makes it easier for phagocytes to engulf a number of pathogens at the same time
2. They act as opsonin causing the antigen-antibody complex to be easily found and engulfed by the phagocytes
54
Types of lymphocytes
T lymphocytes and B lymphocytes
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Where are B lymphocytes made and where do they mature in?
They are made and mature in the bone marrow
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Where are T lymphocytes made and where do they mature in?
They are made in the bone marrow but **mature** in the **thymus gland**
57
Types of T lymphocytes
1. T killer cells
2. T memory cells
3. T helper cells
4. T regulator cells
58
What is the function of T killer cells?
They destroy the pathogen carrying antigen by producing **perforin** which makes holes in the cell membrane of the pathogen making it more permeable
59
What is the function of T helper cells?
1. They have CD4 receptors on their cell surface membrane which bind to surface antigens on APCs
2. They produce interleukin which: stimulates B cells to divide by mitosis increasing the production of antibodies, production of other types of T cells and stimulate phagocytosis
60
What is the function of T regulator cells?
They suppress the immune system acting to control and regulate it. They stop the immune system once a pathogen has been eliminated and make sure the body recognises self antigens and does not set up an autoimmune response
61
Process of cell mediated immunity
Macrophages digest pathogens in phagocytosis. They process the antigens from the pathogen surface to form APCs.
The receptors on some of the T helper cells fit the antigen and this activates the T helper cells to produce interleukin which stimulates more T cells to divide by mitosis. This produces clones of identical activated T helper cells which can either :
• produce interleukin to stimulate phagocytosis
• develop into T memory cells
• develop into T killer cells
• produce interleukin which stimulates B cells to divide
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Types of B lymphocytes
• Plasma cells- they produce antibodies to a particular antigen and release them into circulation
• B memory cells - they remember the antigen and activate the secondary immune response
• B effector cells- these divide to form plasma clones
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What does the humoral immunity respond to in the body?
It responds to antigens found outside the cell e.g. bacteria and fungi and to APC's.
64
Process of the humoural immunity
1. B lymphocytes have antibodies on their cell surface membrane which is complementary to a specific antigen on the pathogen surface. The antibody then engulfs and processes the antigen to become an APC
2. The activated T helper cell uses its T cell receptor to bind to the antigen on the B cell surface. This is clonal selection.
3. The activated T helper cells produce interleukin which activates the B cells to divide by mitosis to give clones of plasma cells and memory cells. This is clonal expansion
4. Cloned plasma cells produce antibodies that fit the antigen on the pathogen surface and either disable them or act as opsonins or agglutinins
5. Some cloned B cells develop into B memory cells that can divide into plasma cell clones to produce antibodies.
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What is clonal selection?
This is when the correct B cell with the correct antibody for a particular antigen is selected for cloning
66
What is the primary immune response?
This is when the body is infected with the pathogen for the first time and triggers an immune response. The antigen triggers the production of T and B cells which produce memory cells that remain in the body for a long time. The T memory cells recognise the antigen if infected for the 2nd time, while the B cells record the antibodies for that antigen
67
Features of the secondary immune system
1. It is faster
2. Memory cells are produced
3. The pathogen enters for the 2nd time
4. Symptoms are not shown
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What happens in the secondary immune response?
Clonal selection happens faster. B memory cells are activated and divide to form plasma cells that produce the right antibody for that antigen. T memory cells divide into the right type of T cells to kill the cell carrying the antigen
69
Compare the main types of T and B lymphocytes- what are their similarities and differences? (6 marks)
Similarities: Both cells form clones of active cells (1); both form memory cells which mean that when they meet a pathogen a second time there is a rapid response, destroying the pathogen before it can cause the disease (1);
Differences: T cells stimulate B cells (1); T cells destroy pathogens directly (1); B cells produce antibodies which act as opsonins stimulating phagocytes to engulf pathogens (1); T cells also regulate immune response so it stops once a pathogen is removed and does not turn against body cells (1)
70
What is an autoimmune disease?
It is when the immune system stops recognising the "self" cells and starts to attack healthy body tissues
71
Discuss the problems that could arise from treating an autoimmune disease with immunosuppressant drugs. (3 marks)
Immunosuppressant drugs reduce activity of immune system (1) preventing/reducing destruction of healthy tissue BUT susceptibility to infection increases (1) as immune system is less effective at recognising pathogens (1)
72
The humoral immune system deals with bacterial and fungal infections but the cell mediated immune system is more effective at tackling viral infections. Explain the biology behind the statement. ( 6 marks)
Humoral immune system response to antigens outside of cell(1); bacterial and fungal cells present in body have antigens to which humoral system can respond (1); system makes antibodies to bacterial and fungal surface antigens, forms antigen-antibody complexes so macrophages readily engulf pathogen (1). Cell mediated system responds to changes in cells (1); Viruses enter the body cells and takes over the cell metabolism (1)
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What are the forms of immunity?
1. Active immunity
2. Passive immunity
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What is active immunity?
It is the type of immunity gotten when one's immune system makes its own antibodies after being stimulated by an antigen
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Types of active immunity
1. Natural immunity
2. Artificial immunity
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What is Natural active immunity?
This is when you become immune after catching a disease. When you meet a pathogen for the first time, your immune system is activated and antibodies are formed, which results in the destruction of the antigen. The immune system produces T and B memory cells so if reinfected by the same pathogen, the immune system recognises it and immediately destroys the pathogen before it causes disease symptoms
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What is artificial active immunity?
This is when you become immune after being injected by a vaccine.
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What is a vaccine?
It is a safe form of an antigen which may contain : dead or inactivated pathogen, altered or detoxified toxin molecules or isolated antigens from the pathogen
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Process of vaccination
1. A vaccine is injected into the bloodstream
2. That triggers the primary immune response to produce antibodies and memory cells
3. If infected with the live pathogen, the secondary immune response is triggered and the pathogen is destroyed before the symptoms of the disease surfaces
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What are vaccines used to prevent?
They are used to help prevent epidemics and pandemic
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What is an epidemic?
It is when a communicable disease spreads rapidly in a population either in a specific location or in a whole country
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What is a pandemic?
It is when the disease spreads across several countries or even the whole world
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What is passive immunity?
It is the type of immunity one gets from being given antibodies made by a different organism
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Types of passive immunity
1. Natural immunity
2. Artificial immunity
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Example of natural passive immunity
A baby becomes immune due to the antibodies it receives from its mother through the placenta and in breast milk called colostrum. The antibodies in the colostrum provides immunity to the baby until its own immune system is developed and can make its own antibodies
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What is artificial passive immunity?
Antibodies are formed in one individual, extracted and then injected into the bloodstream of another individual. An example is tetanus. Infected people will be injected with tetanus antibodies extracted from the blood of a horse, preventing the development of the disease but not providing long-term immunity.
87
What is herd immunity?
This is when the majority of the population is vaccinated against a disease, so the vaccinated people are less likely to get the disease because there is no one to catch it from. This helps prevent the outbreak of the disease/epidemic
88
Influenza is caused by a virus that constantly changes its antigens. Explain why a new influenza vaccine is made every year. (2 marks)
Memory cells produced from vaccination with one strain of the influenza virus will not recognise other strains with different antigens(1), so a new vaccine is made every year to protect against the most recently circulating strains of influenza (1)
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Sources of medicines
Many medicinal drugs are manufactured using natural compounds found in plants, animals and microorganisms. E.g. Penicillin was the first ever antibiotic treatment against bacteria and it was obtained from a fungus.
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Why do we need to protect biodiversity?
We need to protect our biodiversity so we don't destroy a plant, animal or microorganism which could give us a key to a life saving drug
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What are personalised medicines?
They are medicines that are tailored to an individual's DNA. A person's DNA can be used to predict how they'll respond to a drug which can then be used to prescribe drugs that'll be more effective for them
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What is synthetic biology?
It involves using technology to design and make things like artificial proteins, cells and even microorganisms
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What are antibiotics?
They are chemicals that inhibit the growth of bacteria
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What is the biggest issue that arises from using antibiotics?
The development of antibiotic resistant bacteria
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Process of the development of antibiotic resistant bacteria
1. Genetic mutations make some bacteria naturally resistant to antibiotic
2. The bacteria with the antibiotic resistance survives and reproduces and passes on the allele for bacteria resistance onto its offspring so antibiotic resistance becomes common in the population
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Examples of antibiotic resistant bacteria
MRSA and C. difficile
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How can we reduce the likelihood of antibiotic resistant infections?
1. Patients are advised to finish their antibiotic course to reduce the risk of resistant individuals surviving and developing into a resistant strain population
2. Doctors are being encouraged to reduce their use of antibiotics e.g. not prescribing them for minor infections.
