C 3.2 Defense Against Disease Flashcards
(146 cards)
1
Q
What does blood clotting involve?
A
Blood clotting involves a cascade of reactions, each of which produces a catalyst for the next reaction + the events are triggered by blood platelets (cell fragments) and clotting factors.
2
Q
What is blood clotting factors?
A
Clotting factorsare proteins in blood that control bleeding & which are released by platelets.
On surface of these activated platelets, many diffclotting factorswork together in a series of complex chemical reactions.
Clotting must be strictly controlled bc blood clots inside blood vessels can cause blockages. Examples of clotting factors are prothrombin, fibrin or tissue factor (TF).
3
Q
How are cuts sealed by blood clotting (simple explanation)?
A
- Injury to vessel lining triggers release of clotting factors
- Vasoconstriction limits blood flow & platelets form a sticky plug
- Fibrin strands adhere to plug to form an insoluble clot
4
Q
What happens after platelets have collected?
A
After platelets have collected at site of injury, collecting platelets release a clotting factor (a protein called thromboplastin – it is also released by damaged tissues at the site). This clotting factor, along with vitamin K & calcium ions (always present in plasma), causes a soluble plasma protein called prothrombin to be converted to an active, proteolytic enzyme, thrombin. Action of thrombin enzyme is to convert another soluble blood protein, fibrinogen, to insoluble fibrin fibres at site of cut. Within this mass of fibres, red blood cells are trapped & blood clot has formed. Initially it is a gel, which dries to form a hard scab when exposed to the air.
5
Q
What is the role of fibrin in the clotting process?
A
Fibrin forms a mesh that traps platelets and red blood cells, creating a stable blood clot that eventually dries and shrinks to form a scab.
6
Q
How does thrombin contribute to forming a blood clot?
A
Thrombin converts fibrinogen, a soluble clotting factor, into insoluble fibrin.
7
Q
What role does thromboplastin play in the clotting cascade?
A
Thromboplastin, with the help of calcium ions, converts prothrombin into its active form, thrombin.
8
Q
What do platelets and injured tissues release during clotting, and why is this important?
A
They release clotting factors—including calcium ions and thromboplastin—which trigger a cascade of chemical reactions necessary for clot formation.
9
Q
What is the initial step in blood clotting following a skin injury?
A
Platelets are activated and accumulate at the site of injury to form a plug.
10
Q
Why is blood clotting an important defence mechanism?
A
Clotting quickly seals wounds or cuts, preventing pathogens from entering the body through these openings. It also prevents further blood loss and significant fall in blood pressure.
11
Q
What function do commensal bacteria (natural microorganisms on skin) serve in our primary defence system?
A
They naturally reside on the skin, gut, mouth, and nose and can outcompete pathogenic organisms for nutrients and space.
12
Q
How do gastric secretions contribute to defence against ingested pathogens?
A
The hydrochloric acid in gastric secretions creates a low pH that kills most microbes ingested with food.
13
Q
What role do cilia play in defending the respiratory system?
A
Cilia on respiratory epithelial cells in lining of mucous membrane beat in a coordinated way to move mucus and trapped pathogens & harmful particles away from the lungs, facilitating their expulsion via coughing or sneezing or swallowed
14
Q
In which body fluids is lysozyme found and what is its role?
A
Lysozyme is present in mucus, sweat, tears, and saliva, where it helps to kill bacteria.
15
Q
What is mucus?
A
Mucus is a sticky watery solution of glycoprotein with protective (physical barrier) and lubrication functions.
16
Q
What are mucous membranes?
A
Mucous membranes are thinner & softer type of skin. They are found in areas e.g. vagina, foreskin, head of penis & airways leading to lungs.
17
Q
How do mucous membranes trap and eliminate pathogens?
A
They produce sticky mucus which has antiseptic properties as they trap pathogens and contain lysozyme, an enzyme that attacks bacterial cell walls (destroy pathogens).
18
Q
Where are mucous membranes located?
A
They line body cavities & parts open to outside, including digestive, urogenital, & respiratory tracts, as well as mouth, nose, & other ducts.
19
Q
What chemical defence does the skin offer against pathogens?
A
Sebaceous glands associated with hair follicles secrete a fluid (sebum) which maintains skin moisture & lower the skin’s pH, inhibiting bacterial & fungal growth.
20
Q
How does the epidermis (skin) help prevent pathogen entry?
A
Its outer layers consist of dead cells with large amounts of keratin deposits that form a tough, impermeable barrier for pathogens to pass through. It is a physical barrier to entry of pathogen & physical or chemical damage.
21
Q
What are the three layers of the skin?
A
The epidermis, dermis, and hypodermis.
22
Q
What are the primary physical and chemical barriers that form the body’s first line of defence?
A
The skin and mucous membranes.
23
Q
In what way can some pathogens be classified as parasites?
A
Some pathogens are obligate parasites, meaning they rely on their host for energy, nutrition, and other life functions.
24
Q
What are prions and what is an example of a prion-caused disease?
A
Prions are infectious proteinaceous substances that cause neurodegenerative diseases, for example, bovine spongiform encephalopathy (mad cow disease).
25
What distinguishes viruses from other pathogens, and what diseases do they cause?
Viruses require a living cell to replicate. They cause diseases such as the common cold, influenza, measles, mumps, and COVID-19.
26
Define protists and list some diseases they cause.
Protists are diverse unicellular or multicellular eukaryotic organisms. The pathogenic ones can cause diseases like malaria, toxoplasmosis, and sleeping sickness.
27
What are fungi and which diseases are commonly associated with fungal pathogens?
Fungi are unicellular or multicellular eukaryotic organisms; a small percentage are pathogenic and can cause conditions such as ringworm, thrush, and athlete’s foot.
28
What are bacteria and what diseases can pathogenic bacteria cause?
Bacteria are unicellular, prokaryotic organisms found nearly everywhere. Although most are beneficial, some cause diseases like tuberculosis, plague, diphtheria, and cholera.
29
What are the main types of pathogens?
Bacteria, fungi, protists, viruses, and prions.
30
How do pathogens cause disease in the human body?
They invade and live parasitically in the body, and diseases occur when they pass from an infected host to a healthy individual.
31
What are pathogens?
Pathogens, also called infectious agents, are organisms that cause disease and serve as the starting points in the chain of infection.
32
What is amoeboid movement?
A type of locomotion that involves the protrusion of pseudopodia.
33
What is a monocyte?
Largest type of specialised white blood cells or leukocytes capable of amoeboid movement., defending the immune system by destroying or damaging pathogens, including viruses, bacteria and fungi.
34
What is a neutrophil?
Most abundant type of specialised white blood cells or leukocytes capable of amoeboid movement. of white blood cells, They are usually the first line of defence against pathogens, targeting mainly bacteria and fungi.
35
What is a macrophages?
A type of white blood cell that engulfs and kills microorganisms, removes dead cells, and stimulates the action of other immune system cells.
36
What is a pseudopodia?
Literally ‘false feet’, they are temporary arm-like projections or extensions used for movement and feeding.
37
What is the primary role of the immune system?
To protect the body from pathogens and foreign substances by distinguishing self from non-self.
38
What are the two main branches of the immune system?
The innate immune system and the adaptive immune system.
39
What is innate immunity?
Immunity present from birth that provides rapid, non-specific defence against pathogens. The innate immune system responds to broad categories of pathogen. It does not change during an organism’s life. Phagocytes are part of the innate system.
40
How does the innate immune system respond to pathogens?
It uses physical and chemical barriers—such as the skin, mucous membranes, and phagocytosis—to prevent or limit pathogen spread.
41
Is the response of the innate immune system specific to particular pathogens?
No, it responds in a similar manner to any potential pathogen without tailoring the response.
42
What is the adaptive immune system?
Adaptive immune system responds in a specific way to particular pathogens. It builds up a memory of pathogens it has encountered, so it offers more effective protection against common infectious diseases. Antibody-producing lymphocytes are part of the adaptive system.
43
What triggers the adaptive immune system?
It is activated when the innate immune system is unable to fully control an infection.
44
Which cells mediate the adaptive immune response?
Lymphocytes, a type of white blood cell.
45
What is one key feature that distinguishes the adaptive immune system from the innate immune system?
Specificity—it targets particular pathogens with a tailored response.
46
What is another important feature of the adaptive immune system?
Memory—the system “remembers” pathogens for a faster, enhanced response during subsequent infections.
47
Do the innate and adaptive immune systems work independently?
No, they constantly communicate and work together to provide an effective immune response.
48
What is the second line of defence in the human body?
Second line of defence is mostly implemented by phagocytic branch of white blood cells. In addition, cells such as dendritic cells & macrophages activate an inflammatory response, secreting proteins called cytokines that trigger an influx of defensive cells from blood.
49
What is a phagocyte?
Phagocyte = large, irregularly shaped leukocytes cells that remove bacteria, viruses, cellular debris & dust particles. Diff phagocytes cells work in diff locations: neutrophils circulate in blood, while macrophages are found in lymph, tissue fluid, lungs & other spaces, where they kill microbes before they enter blood.
50
What is phagocytosis?
A process where specialized white blood cells ingest and digest foreign material, including pathogens.
51
Which cells are known as professional phagocytes?
Monocytes, neutrophils, and macrophages.
52
What kind of movement allows phagocytes to reach the site of an infection?
Amoeboid movement, which enables them to migrate from the blood to the affected tissues.
53
What is the first step in the process of phagocytosis?
Recognition of the pathogen (bacterium) by receptor molecules on the plasma membrane of phagocytic leucocyte.
54
After recognition, how do phagocytes begin to engulf the pathogen?
Bacterium becomes attached to receptor molecules on plasma membrane of leucocyte, through extend pseudopodia that bind to and surround the pathogen.
55
What structure is formed when pseudopodia encircle the pathogen?
A vesicle called a phagosome is formed when trapped bacterium engulfed into a food vacuole in cytoplasm of leucocyte.
56
What happens during phagosome maturation?
The phagosome undergoes changes preparing it for fusion with lysosomes.
57
What is formed when the phagosome fuses with lysosomes?
A phagolysosome.
58
What role do the lysosomal enzymes play in phagocytosis?
They digest the microbial components inside the phagolysosome, through lysosomes in cytoplasm fusing with vacuole & discharging hydrolytic enzymes
59
What is the end result of phagocytosis?
The pathogen (bacterium) is broken down into its constituent molecules, and these are dispersed into the cytoplasm. 'rubbish-collecting' leucocytes are distributed widely in body - they engulf larger debris & damage cells, and dispose of them.
60
How would you compare the speed of the innate immune response with that of the adaptive immune response?
The innate immune response is rapid and immediate, whereas the adaptive response is slower to develop.
61
What advantage does immunological memory provide?
It allows for a faster and more effective response upon re-infection with the same pathogen.
62
Why is distinguishing self from non-self critical for the immune system?
It prevents the immune system from attacking the body’s own cells while targeting foreign invaders.
63
What general defence mechanisms are employed by the innate immune system?
Physical barriers (skin and mucous membranes) and generalised cellular responses like phagocytosis.
64
How does the adaptive immune system complement the innate immune system?
It provides a specific, long-lasting response that targets pathogens more effectively when the innate defences are insufficient.
65
Which immunity retains memory?
Adaptive immunity retains a memory of the pathogen ensuring a more effective and enhanced immune response on subsequent exposure to the same pathogen.
66
What is the third line of defence in the human body?
3rd line of defence = adaptive or specific immune response & usually takes longer to come into effect after 1st & 2nd lines of innate immune system. Adaptive immune system response typically results in production of antibodies, which then circulate in blood stream & are contained in lymph nodes.
67
How are lymphocytes different from each other.
Each B cell is programmed to make one specific antibody. When a B cell encounters its specific or eliciting antigen it changes into an antibody producing cell.
68
What is an antigen?
Antigen: A substance or molecule, often found on a cell or virus surface that stimulates production of antibodies (characteristic to surface of a cell/cell type).
69
What is an antibody?
Antibody: A protein produced by lymphocytes in response to an antigen that. It recognizes a specific antigen & binds to it as part of an immune response.
70
How does immune cells recognize foreign cell (pathogens)
Surface antigens are found on viral cells, bacterial cells & all animal cells including red blood cells. It is these cell surface antigens (or proteins) which cells of immune system recognizes as self or as foreign.
71
What are two important surface antigens of influenza virus?
Influenza virus has two important surface antigens important for virus replication:
1. hemagglutinin and
2. neuraminidase.
Antivirals can act on these proteins to fight infections.
72
How are B-lymphocytes activated?
For B lymphocytes to become antibody producing cells it involves presentation of antigens on a cell, Hepler T-cell (e.g. phagocyte which has ingested a microbe) on specific receptors, followed by an activation of killer T-Cells and B-lymphocytes. Neither a B-cell, nor a T-cell can be activated on its own. Instead, it must come across an antigen-presenting cell that “displays” a matching antigen on its MHC proteins.
73
What is a phagocyte?
Phagocyte = White blood cells that engulf, absorbs & digest pathogens, foreign particles & cell debris.
74
What is T-Lymphocyte?
T-Lymphocyte = White blood cells processed by thymus that are responsible for cell-mediated immunity
75
What is B-Lymphocyte?
B-Lymphocyte = Lymphocyte that produce antibodies & are responsible for presenting antigens to T-cells. Once activated, they can mature into plasma cells or memory B-lymphocytes
76
What is B-Plasma cells?
B-Plasma = type of immune cell that makes large amounts of a specific antibody. Plasma cells develop from B-cells that have been activated.
77
What is B-Memory cells?
B-Memory cells: long-lived lymphocyte capable of responding to a particular antigen on its reintroduction, long after exposure that stimulated its initial production.
78
Where is class II MHC found?
Class II MHC (major histocompatibility complex) is found on antigen presenting cells and triggers an immune response.
79
What are naive lymphocytes?
Lymphocytes (B-cells and T-cells) that have not yet encountered their specific antigen.
80
What are effector cells in the context of lymphocytes?
Lymphocytes that have encountered their specific antigen and become activated to mount an immune response.
81
What is the significance of having a specific B-cell and T-cell for every antigen?
It ensures that the immune system can recognize and respond to an enormous variety of antigens with precision.
82
How do lymphocytes become activated from their naive state?
They encounter their specific antigen in the secondary lymphoid organs, which triggers their conversion into effector cells.
83
What role do phagocytes play in activating helper T-cells?
They digest pathogens and retain fragments (antigens) that are later presented by antigen-presenting cells (APCs) to helper T-cells.
84
What is the function of antigen-presenting cells (APCs) in the immune response?
APCs display antigen fragments on their surface to activate specific helper T-cells.
85
What happens when a helper T-cell is activated?
It increases in number (clonal expansion), activates B-cells specific to the same antigen, and also activates cytotoxic T-cells.
86
How does the activation of helper T-cells contribute to the overall immune response?
By coordinating the activation of both B-cells (for antibody production) and cytotoxic T-cells (for killing infected cells).
87
What are the two integrated events required for B-cell activation?
First, the B-cell receptor must bind to its specific antigen; second, an activated helper T-cell that recognizes the same antigen must provide additional stimulation.
88
How are B-lymphocytes activated to form clones of antibody producing cells?
1. B cells recognize antigens with specific receptors. B-cells differ in antigen specificity.
2. Activated B cells divide many times by mitosis, generating a clone of plasma cells which all produce same antibody type. This is called clonal selection.
3. Antibodies are released from plasma cells & circulate in blood stream for several weeks.
4. Most of clones turn into active plasma cells, but some differentiate into memory B-cells.
89
What are plasma cells?
Plasma cells are mature B lymphocytes which secrete a large number of antibodies during an immune response.
Plasma cells have a large number of rER, which manufactures, modifies and transports antibodies.
90
What are the protective mechanism of binding antibodies to antigens?
- Agglutination
- Activation of complement
- Opsonization
- Antibody-dependent cell-mediated cytotoxicity (two types: protein antigens stick out of pathogen or release enzymes to destroy cell from inside)
- Neutralization
91
What is the clonal selection theory?
The theory that once a B-cell is activated by its specific antigen, it divides repeatedly to produce clones, all of which recognize the same antigen.
92
What occurs during the multiplication of activated B-cells?
They undergo repeated mitotic divisions to form many clones that are all specific to the antigen encountered.
93
What are plasma cells and what is their function?
Plasma cells are differentiated B-cells that produce and secrete large quantities of antibodies specific to the antigen.
94
What role do antibodies play in the immune response?
They bind to antigens, neutralizing them or marking them for destruction by other immune cells.
95
What are memory B-cells and why are they important?
Memory B-cells are long-lived cells that remain in the bloodstream and lymph nodes, “remembering” the antigen for a rapid response upon reinfection.
96
How does the activation of helper T-cells lead to clonal expansion?
Once activated, helper T-cells multiply, increasing the pool of cells available to activate B-cells and cytotoxic T-cells that recognize the same antigen.
97
In the activation process, what indicates that a B-cell has successfully recognized an antigen?
The B-cell receptor on its surface binds specifically to the antigen.
98
Why is the stimulation by an activated helper T-cell critical for B-cell activation?
It provides a necessary second signal that ensures the B-cell is activated only in the presence of the correct antigen, thereby preventing inappropriate responses.
99
What is the overall result of the interaction between T-lymphocytes and B-lymphocytes?
The coordinated activation and clonal expansion of lymphocytes lead to the production of antibodies, elimination of the pathogen, and establishment of immunological memory.
100
How does the immune system “remember” an antigen for future protection?
Through the formation of memory B-cells, which remain dormant until the same antigen is encountered again.
101
What does the term “clonal expansion” refer to in the context of B-cell activation?
It refers to the process where a single activated B-cell divides to produce many identical clones that all recognize the same antigen.
102
How do plasma cells and memory cells differ in their roles?
Plasma cells produce antibodies to fight the current infection, while memory cells provide long-term immunity by “remembering” the antigen for future responses.
103
What triggers the transition from a primary to a secondary immune response?
The presence of memory B-cells generated during the primary response, which rapidly differentiate into plasma cells upon re-exposure to the antigen.
104
What is the significance of having both humoral and cell-mediated responses during an immune reaction?
It ensures that the body can neutralize free pathogens with antibodies (humoral immunity) and eliminate infected cells via cytotoxic T-cells (cell-mediated immunity).
105
Why is the described process considered a simplified version of lymphocyte activation?
Because the complete process involves additional complex signalling pathways and interactions that are beyond the scope of this overview.
106
What is a disease?
Disease = particular kind of illness, with characteristic symptoms
107
What are the three main causes of disease?
1. Genetic - alleles a person has
2. Environmental - e.g. toxic chemicals or radiation
3. Infection with a pathogen
108
What is a pathogen?
A pathogen is a disease-causing organism. They are passed from one infected organism to another.
They enter the organism, multiply there and cause harm. Typically, term is used to describe an infectious agent e.g. virus, bacterium, protozoa, or a fungus. Pathogens are therefore microorganisms. Scientific study of pathogens = Pathology.
109
What can also cause diseases?
Prions & helminthic parasites can also cause diseases. e.g. CJD (Creutzfeldt-Jakob disease) = human version of a group of infectious diseases which affect brain = spongiform encephalopathies. Causative agent has been found to be a prion, rather than a microorganism or virus. Prions = protein molecules which enter body & reach brain tissue where they cause more proteins already there to turn into prion molecules causing brain cells to malfunction, lading to development of disease. e.g. organisms that invade body & can be seen with naked eye, such as tapeworms, are usually considered to be parasites rather than pathogens.
110
how can pathogens get transmitted with examples?
- Inhaled droplets e.g. Influenza virus
- Direct contact e.g. Herpes (virus), Varicella (virus)
- Bodily fluids e.g. strep throat, HIV
- Animal vectors e.g. Rabies (virus), malaria (protozoa), Lyme's (protozoa)
- Blood contact e.g. Hepatitis virus
- Ingested/swallowed e-g- Salmonella (bacteria)
111
What is bacteria pathogen? How is it transmitted? And what are examples?
- Don`t have a real nucleus (instead they have a nucleoid)
- They are prokaryotes
- Divide by binary fission (asexual reproduction)
- Cell walls composed of peptidoglycan
- Infectious & non-infectious kind
- They can cause: Food poisoning, salmonella, conjunctivitis, strep throat, cholera…
112
What is virus pathogen? How is it transmitted? And what are examples?
- Don`t have nucleus but have DNA
- Need to attach to another cell to reproduce
- Are not considered as cells
- Cannot be killed by antibiotics
- Cause of flu, common cold, HIV, Herpes,…
113
What is fungus pathogen? How is it transmitted? And what are examples?
- They have a nucleus & polysaccharide chitin in their cell walls
- They are eukaryotes
- Reproduce by producing spores
- They can cause Athlete`s foot, mould, ringworm, allergic reactions
114
What are protozoan parasites pathogen? How is it transmitted? And what are examples?
- Often parasitic or symbiotic organisms
- Unicellular eukaryotes, making treatment difficult
- They can cause Malaria, Leishmaniosis, Giardia, Trypanosoma, Sleeping sickness, Lyme’s disease…
115
What are helminthic parasites pathogen? How is it transmitted? And what are examples?
- Parasitic diseases
- Multicellular & eukaryotic
- They can cause Elephantiasis, Schistosomiasis, Toxocariasis, Pinworm, Roundworm or tapeworm infections
116
How can microbes cause diseases in the human body?
Many diff microbes can grow inside human body & cause a disease. Some are opportunistic &, although they can invade body, they also commonly live outside it. Others are specialised & can only survive inside a human body.
117
What is zoonosis?
Zoonosis is when a pathogen can be transmitted to humans from other animals. Usually viruses are specific to their host, with a very narrow rang of hosts. Sometimes viruses can use more than one species as a host.
118
What are examples of zoonotic diseases?
- Measles
- Syphilis
- Bubonic plague
- Lyme disease
- West Nile virus
- Rocky Mountain spotted fever
119
Why are zoonotic diseases increasing?
There are many reasons why there seems to be an increased appearance of these diseases. Mostly, the underlaying cause seems to be the closer contact between animals and humans.
E.g. live animal markets, wildlife hunting, intensive wildlife farming and domestic animals.
120
What is pathogen causes Tuberculosis? What is the animal host? What is the mode of human infection?
Pathogen = Mycobacterium tuberculosis
Cattle
Direct contact (air germ) or ingestion (infected milk)
121
What is pathogen causes Rabies? What is the animal host? What is the mode of human infection?
Pathogen = Rabies virus Lyssavirus
Dog
Bite & saliva
122
What is pathogen causes Japanese encephalitis? What is the animal host? What is the mode of human infection?
Pathogen = Japanese encephalitis virus
Mosquito
Mosquito bite
123
What is pathogen causes Lyme's disease? What is the animal host? What is the mode of human infection?
Pathogen = Borrelia burgdorferi
ticks
Tick bite
124
What is HIV? -how does it infect a cell?
HIV is a retrovirus is a virus that uses RNA as its genetic material. When a retrovirus infects a cell, it makes a DNA copy of its genome that is inserted into DNA of host cell.
125
When was HIV discovered? And what was it's description?
HIV was first identified in 1983. HIV is a tiny virus, less than 0.1 μm in diameter. It consists of two single strands of RNA which, together with enzymes, are enclosed by a protein coat. A membrane, derived from human host cell in which virus was formed, encapsulates each new virus particle leaving host cell.
126
How does HIV reproduce and form new mature virus particles?
1. Glycoprotein on viral envelope bind to specific receptor molecules on host cell, promoting viral entry into cell
2. Capsid & viral genome enter cell. Digestion of capsid cellular enzymes releases viral genome
3. Viral genome functions as a template for synthesis of complementary RNA strands by a viral RNA polymerase
4. New copies of viral genome RNA are made using complementary RNA strands as templates
5. Complementary RNA strands also function as mRNA, which is translated into both capsid proteins (in cytosol) & glycoproteins for viral envelope ( in ER & Golgi apparatus)
6. Vesicles transport envelope glycoproteins to plasma membrane
7. Capsid assembles around each viral genome molecule
8. Each new virus buds from cell, its envelope studded with viral glycoproteins embedded in membrane derived from host cell
127
What is the consequences of an HIV infection?
HIV attacks T – helper cells (CD4+ cells), causing their numbers to drop. As a result, immune system is weakened & fewer antibodies can be produced & diseases develop. Once CD4+ cells drop below a critical level, immune system is ineffective, & patient has AIDS - Acquired Immune deficiency Syndrome. Patients with AIDS are very susceptible to opportunistic infections, which may prove lethal.
128
How can HIV be transferred?
- sex without a condom/ unprotected sexual intercourse with an infected partner
- sharing injecting equipment
- passed from mother to baby e.g. in utero, during delivery or breastmilk
-contaminated blood transfusion & organ
129
How can HIV not be transmitted?
- saliva on a drinking glass
- sharing a towel
- sneezes & coughs
- insect bites e.g. female mosquito transmit HIV when feeding on human blood
- hugging
- kissing
- sharing food
- bathing
- sweat
130
What are antibiotics?
Antibiotics = chemicals that block processes occurring in bacteria but not in eukaryotic cells
An antibiotic is a chemical that inhibits growth of microorganisms. Most antibacterial antibiotics were discovered in saprotrophic fungi. E.g. penicillin – it is produced by some strains of Penicillium fungus in competition with bacteria for nutrients.
131
What is mechanism of action of antibiotics?
Most antibiotics disrupt metabolism of prokaryotic cells (e.g. cell wall synthesis, proteins synthesis, folic acid synthesis, cell membrane synthesis or DNA/RNA synthesis) – whole populations of bacteria may be quickly suppressed.
132
What antibiotics not affective against?
- Viruses
-eukaryotic cells
133
Why are antibiotics not effective against viruses?
Viruses have diff metabolic pathways to bacteria – so antibiotic drugs have nothing to target. Viruses use host cell metabolism to reproduce & spread. Viruses are non-living & can only reproduce when they are inside living cells. Instead of having a metabolism of their own they use host cell’s machinery for transcription & protein synthesis, as well as enzymes for ATP synthesis. Therefore, these processes cannot be targetted by antibiotics.
134
Why are antiviral drugs effective against viruses?
- Interferons stimulate immune system to prevent replication of invading virus.
- Some antivirals target specific proteins
- Many others target a specific stage of viral life cycle
135
What is an example of bacteria resistant to antibiotic?
Sometimes bacteria become resistant to antibiotic e.g. Methicillin Resistant Staphylococcus Aureus (MRSA) (infections of blood & surgical wounds of hospital patients) = resistant bacterial strain. MRSA is any strain of Staphylococcus aureus that has developed, through process of natural selection, resistance to beta-lactam antibiotics.
136
How do bacteria become resistant to antibiotic?
Development of antibiotic resistance = example for evolution by natural selection. Genetic variation from a mutation (e.g. an antibiotic resistance gene) is selected for in environment giving cell a selective advantage.
1. A bunch of bacteria including a resistant variety get bathed in antibiotics
2. Most of normal bacteria die.
3. Resistant bacteria multiply & become more common
4. Eventually, entire infection evolves into a resistant strain
This cell will survive when antibiotic is around & give rise to future pop.
137
How can you test susceptibility of bacterial strain to antibiotics?
Susceptibility of bacterial strains to antibiotics can be shown with help of diffusion disk assays. Testing resistance of microbes in lab e.g. Petri dishes contain lawns of bacteria (creamy yellow) cultured from two diff clinical samples. White filter paper discs each contain diff antibiotics. Where clear zones appear around the discs, bacterial growth has been prevented by antibiotic.
138
How can bacteria resistance be avioded?
- Doctors prescribing antibiotics only for serious bacterial infections
- Patients completing courses of antibiotics
- Hospital staff maintaining high standards of hygiene to prevent cross infection
- Farmers not using antibiotics in animal feeds to stimulate growth
- New types of antibiotics need to be introduced
139
What are vaccines?
Vaccines which contain attenuated versions or antigens of a pathogen are introduced into body by injection (e.g. flu vaccination) or orally (e.g. polio). Aim of vaccination is to cause a primary immune response by principle of challenge & response.
140
How do vaccines work?
It stimulates an immune response – if actual microorganism enters body as a result of infection, it will be destroyed by antibodies in a secondary immune response.
141
What are vaccines made from?
Vaccines can be made from many diff molecular components originating from pathogen. Occasionally, type of agent causes a different category of antibodies from being produced.
142
What is primary immune response?
The primary immune response occurs when an antigen comes in contact to immune system for first time. During this time immune system has to learn to recognize antigen & how to make antibody against it & eventually produce memory lymphocytes. It is slower & less robust bc it relies on the activation of naive lymphocytes.
143
What is secondary immune response?
Secondary immune response occurs when second time (3rd, 4th, etc.) person is exposed to same antigen. At this point immunological memory has been established & immune system can start making antibodies immediately. A faster & stronger response upon re-exposure to same antigen due to rapid activation of memory B-cells.
144
What is active immunity?
Active immunity is immunity due to production of antibodies by organism itself after immune response has been stimulated by a pathogen
145
What is passive immunity?
Passive immunity is immunity due to acquisition of antibodies from another organism, in which active immunity has been stimulated. This includes artificial sources, as well as colostrum or placenta.
146
What is herd immunity?
Herd immunity is when majority of pop is covered by vaccine. When herd immunity exists, even those few who are unvaccinated are protected from infection.
