4.1.1 Disease and the immune system

Question 1

What is a non-specific immune response?

Answer 1

-a system that works in the same way for all pathogens, whatever foreign antigen it has
-always present and activated rapidly

Question 2

Non-specific defence barriers

Answer 2

-the skin
-mucous membranes
-expulsive reflexes
-lysozymes
-blood clotting

Question 3

The skin

Answer 3

-acts a physical barrier covering the body to prevent entry of pathogens
acts a chemical barrier:
-it has a skin flora of healthy microorganisms that outcompete pathogens for space on the body surface
-produces chemicals that are antimicrobial(help destroy/slow down the growth of microorganisms) and can lower pH, which inhibits growth of pathogens(produces sebum)
-i.e skin cells secrete fatty acids that can kill some bacteria and lower pH so it is harder for pathogens to colonise
-i.e skin cells secrete lysozyme, which catalyses breakdown of carb in the cell walls of some bacteria

Question 4

Mucous membranes

Answer 4

-many body openings/tracts i.e nose, ears that are exposed to the environment have membranes that can secrete sticky mucus to trap microorganisms
-contain lysozymes which destroy bacterial and fungal cell walls + phagocytes which remove remaining pathogens
-i.e lung epithelium are lined with mucus and have cilia which beat to waft away pathogens(phlegm coughed out through trachea up to throat or swallowed so HCl in stomach breaks it down)

Question 5

Expulsive reflexes

Answer 5

-coughs and sneezes expel pathogen-laden mucus from gas exchange system after irritation from substance i.e dust
-vomiting and diarrhoea expel contents of gut along with infective pathogens

Question 6

Lysozymes

Answer 6

-enzymes in tears, urine and stomach acid which help prevent pathogens getting into our bodies

Question 7

Blood clotting

Answer 7

-Pathogens can enter body through a cut as your skin is breached
-Blood clots are a mesh of protein fibres that seal wounds(prevent pathogen entry and blood loss)
-formed by cascade of chemical reactions when platelets come into contact with collagen in skin or the wall of a damaged blood vessel and begin secreting several substances i.e thromboplastin and serotonin

Question 8

What do thromboplastin and serotonin do?

Answer 8

• T is an enzyme that triggers cascade of reactions which result in the formation of fibrin
  which itself forms a network, trapping platelets
  and forming a blood clot
• S makes smooth muscle in the walls of blood vessel contract, so they narrow and reduce blood supply to the area

Question 9

Wound repair

Answer 9

-clot dries out, forming a hard and tough scab that acts as barrier against pathogens
-Epidermis cells below scab divide and migrate to the edges of the wound while damaged blood vessels regrow
-tissue below the wound contracts to bring the edges of the wound closer together + collagen fibres are deposited to give tissue strength(too much collagen= scarring)
-once epidermis reaches normal thickness, the scab comes off and wound is healed

Question 10

What is the immune response?

Answer 10

-The body’s response to a foreign antigen*/ pathogen that got past primary defences
-it involves a non specific response which is the same for all pathogens and a specific response which is antigen specific
* i.e blood cells reject other blood type

Question 11

Symptoms of the inflammatory response

Answer 11

(localised response to pathogens)
-pain, heat, redness and swelling of tissue

Question 12

Steps of the inflammatory response

Answer 12

1) Mast cells(white blood cells) become activated when they detect damaged tissue and release chemicals called cytokines and histamines
2) Histamines causes:
- heat and redness by vasodilation(widening blood vessels) which increases blood flow to affected area(more white blood cells to fight pathogen) + temp increase helps prevent pathogens reproducing
- pain and swelling by making capillaries more ‘leaky’/increasing permeability of blood vessels, to allow specific white blood cells to leave blood plasma and join tissue fluid(then drain into lymphatic system and take pathogen to lymph nodes which become inflamed)
3) Cytokines are cell signalling chemicals that inform + attract phagocytes to the site of pathogen for phagocytosis to occur

Question 13

How do fevers occur and why are they a good adaptation?

Answer 13

-cytokines stimulate hypothalamus to reset at a higher temp when pathogen invades
-useful because pathogen reproduction is best at 37 degrees or lower so it is inhibited
-specific immune system works better at higher temps

Question 14

What are phagocytes?

Answer 14

-specialised white blood cells that engulf and destroy pathogens:*neutrophils & macrophages
-build up at a site of infection to attack pathogens(pus consists of dead neutrophils and pathogens)
*first white blood cell to respond to a pathogen inside the body

Question 15

neutrophil structure

Answer 15

-multilobed nucleus= can squeeze through fenestrations to get to blood and tissue
-lysosome= vesicle with digestive enzymes

Question 16

Phagocytosis- neutrophils

Answer 16

• role is to digest as many pathogens as possible
  1) will recognise an antibody tagged to the pathogen that marks it as foreign(opsonin attach to antigens to aid this)
  2) engulf the pathogen by changing the cytoskeleton structure of neutrophil
  3) pathogen is enclosed in a vesicle called a phagosome, which then combines with a lysosome to form a phagolysosome
  4) enzymes from lysosome digest + destroy pathogen
  5) our body will recycle what we can i.e amino acids and the rest is released via exocytosis

Question 17

Structure of macrophages

Answer 17

-lysosome= vesicle with digestive enzymes
-nucleus
-MHC complex= glycoproteins in the cytoplasm which help form an antigen presenting cell(APC)

Question 18

Phagocytosis- macrophages

Answer 18

• starts the specific immune response
  1) all the same steps as with a neutrophil except that a phagolysosome will not digest the antigen of the pathogen
  2) MHC complex combines with the antigen and moves to the cell surface of the macrophage
  3) This forms an antigen presenting cell

Question 19

What are Opsonins?

Answer 19

-chemicals that bind to pathogens and ‘tag’ them so they can be easily recognised by phagocytes
-receptors on phagocyte’s cell membrane bind to common opsonins that act as constant region so phagocyte can then engulf pathogen

Question 20

The specific immune system

Answer 20

-slower than non specific responses BUT immune memory cells mean secondary responses are very quick

Question 21

Role of antigens

Answer 21

-on the surface of all cells and the body can recognise the difference between self antigens and non-self antigens(on pathogens)
-some toxins can act as antigens
-trigger immune response involving production of proteins called antibodies
-can bind to antibody to form antigen-antibody complex(similar to lock and key mechanism)
-there is a specific antibody for each antigen

Question 22

Structure of antibodies

Answer 22

-Y shaped glycoproteins/immunoglobulins (proteins with carbohydrate group attached)
- 4 polypeptide chains= 2 long heavy chains and 2 short light chains
- chains are held together by Disulfide bridges(very strong bonds)
each chain has:
-2 variable regions where the antibody forms antigen-binding sites, shape is specific to complementary antigen, regions DIFFER for antibodies
-constant region which is the same sequence of amino acids in every antibody, allow binding to receptors on immune system
-hinge region gives antibody flexibility, allows it to bind to more than one pathogen

Question 23

How do antibodies help clear infection?

Answer 23

• act as opsonin so antibody-antigen complex(tag pathogens) is easily identified and digested by phagocytes
• act as agglutinins causing pathogens to clump together, to help prevent them spreading + make it easier for phagocyte to engulf large volume when it binds (specialised with 2 variable regions + hinge region)
• act as anti-toxins= neutralise the toxins produces by pathogens by binding to it and preventing it from affecting human cells–} toxin-antibody complexes are phagocytosed

Question 24

Primary immune response(specific)

Question 25

Where do lymphocytes mature?

Answer 25

-B lymphocytes mature in the Bone marrow -T lymphocytes mature in the Thymus gland

Question 26

Cell mediated response(T cells)

Answer 26

-Clonal selection: macrophages form antigen-specific cells + receptors of T helper cells(white blood cells with lots of receptors) that are specific to the antigen will bind to APCs and become activated -Clonal expansion: when activated, Th cells produce interleukins which stimulate more T cells to divide rapidly by mitosis forming clones with the specific antigen -Differentiation: cloned T cells may: - develop into T memory cell(rapid 2ndary response) - T helper cell= produce interleukins(cell signalling proteins, type of cytokine) that detect APCs + stimulate phagocytosis / stimulate B cell division in PLAs - T regulator(suppress immune system + slow it down to prevent auto-immune diseases) - T killer cells(destroy pathogen by binding to it and secreting perforin which makes holes in cell membrane + kills cells i.e cancer cells, virus infected cells)

Question 27

Humoral response

Answer 27

-B lymphocytes(type of white blood cell covered with antibodies, different shape on each membrane complementary to antigen) -B-cell with complementary antibody engulfs pathogen -Clonal selection: Activated T helper cells bind to the B-APC with the correct antibody to overcome a specific antigen -produces more activated T helper cells(release interleukins) activate the B cells -Clonal expansion: activated B cell divides by mitosis to give clones of B plasma cells and B memory cells -Differentiation: B effector cells divide to form plasma cells(PLA) which produce lots of antibodies that fit the antigens on the surface of pathogens and form a-a complexes: could be agglutinins, antitoxins or opsonins

Question 28

Primary vs Secondary immune response

Answer 28

- primary: -when the pathogen enters the immune system for the 1st time -very slow, can take days/weeks to become fully effective against specific pathogen because there aren't many B lymphocytes that can make specific antibody until memory cells -activates B and T lymphocytes -person undergoes symptoms - secondary: happens if you get exposed to the same pathogen again - the volume of antibodies produced is higher in a shorter amount of time & is a rapid response,(clonal selection happens faster) -memory B cell produce lots of plasma cells quickly= lots of antibodies quickly -memory T cells produce lots of T killer cells quickly to kill pathogens quickly -no symptoms show

Question 29

What is cell signalling and why is it important?

Answer 29

-it is how cells communicate and it is important because it helps to activate the different types of white blood cells that are needed -i.e cytokines inform other phagocytes when the body is under attack and stimulate them to move to the site of infection, and can increase body temp -i.e T helper cells release interleukins which activate B lymphocytes by binding to receptor to signal presence of a pathogen

Question 30

Blood smears

Answer 30

-sample of blood is smeared over a microscope slide -stains are added to the sample to make different cells more distinguishable i.e rbcs, wbcs and platelets(tiny fragments involved in blood clotting) -some wbcs have granules in their cytoplasm so they look grainy -i.e monocyte is the biggest white blood cell, type of phagocyte, kidney bean shaped nucleus and non grainy cytoplasm -lymphocyte is smaller than neutrophil, big nucleus, very little cytoplasm, can distinguish between B and T under light microscope -neutrophil has a multilobed nucleus, grainy cytoplasm

Question 31

Maintaining immunity

Answer 31

-memory B and T lymphocytes have a limited lifespan and when they die the person becomes susceptible to disease again -immunity maintained by continuously exposing to pathogen to produce more new memory cells -i.e areas with high malaria become immune to it

Question 32

What are the 4 types of pathogens?

Answer 32

-Bacteria -Viruses -Protoctista -Fungi

Question 33

Bacteria

Answer 33

-prokaryotes(unicellular, no membrane-bound nucleus or organelles)—> naked DNA and plasmids help develop resistant genes -can be rod shaped(bacilli), spherical(cocci), comma shaped(vibrios), spiralled(spirila) and corkscrew(spirochaetes) -Gram positive bacteria look purple-blue under a light microscope and Gram negative bacteria appears red--} different types of cell wall which affect how bacteria reacts to antibiotics(kills/inhibits growth of bacteria) -cause disease predominantly by producing toxins that harm the host(inhibit enzyme action)

Question 34

Viruses

Answer 34

-non living infectious agents (0.02-0.3 um diameter and around 50x smaller than bacteria) -some genetic material(DNA/RNA) surrounded by protein -spread through contacts -invade living cells by injecting genetic material into host cell and combining it with host cell DNA to make more viruses using host cell’s biochem i.e bacteriophages take over bacteria + use it to replicate while killing it -reproduce rapidly and develop adaptations to their host -can cause disease in every other type of organism -hard to find a cure that won’t damage host cell DNA

Question 35

Protoctista

Answer 35

-group of eukaryotic organisms(single celled) with wide variety of feeding methods to digest cells(affect both plants and animals) -incluse single-celled AND colony groups -parasitic: use people/animals as host to reproduce -pathogenic: need vector to transfer them to hosts i.e mosquitoes + water

Question 36

Fungi

Answer 36

-affects plants more -eukaryotic organism, often multicellular(yeast is exception, causes thrush etc) -cannot photosynthesise and digest food **extracellularly**(secrete enzymes through cell membrane onto food to break it down then pass it into cell to absorb nutrients) -some can be parasitic, so feed on living plants and animals(pathogenic fungi) -saprotrophic fungi digest decayed matter -reproduce to produce millions of tiny spores which spread wide distances so they are rapid(lead to starvation + hardship) -produce toxins

Question 37

Animal diseases: TB

Answer 37

-bacterial -affects mostly humans and cattle -damages and destroys lung tissue and suppresses immune system(less able to fight other diseases) -HIV/AIDS make you more susceptible to TB **curable by antibiotics and preventable by improving living standards and vaccines**

Question 38

Animal diseases: Bacterial meningitis

Answer 38

-bacterial -affects the meninges of the human brain(protective memebranes) -can spread and cause blood poisoning and rapid death -blotchy red/purple rash that doesn't disappear when a glass is pressed on it(15-19 year olds mainly) -10% victims die and 25% get some permanent damage **cured by antibiotics if early and vaccines can protect some forms**

Question 39

Animal diseases: HIV/AIDS

Answer 39

-caused immunodeficiency **virus** -affects humans and some non-human primates -retrovirus with RNA as its genetic material -reverse transcriptase enzyme transcribes RNA to single stranded DNA in the host cell which interacts with the genetic material of host and produce viral proteins -targets T helper cells of the specific immune system + gradually destroys it so they become susceptible to other infections -passed via bodily fluids i.e unprotected sex, sharing needles **no vaccine/cure but antiretroviral drugs slow process of disease for more healthy years**

Question 40

Animal diseases: Influenza

Answer 40

-viral infection(A virus, most virulent) -affects animals and humans -kills ciliated epithelial cells in gas exchange system leaving airways open to secondary infection(lead to other fatal illnesses) -young/old + chronically ill most affected -virus mutate regularly, surface antigens changing leads to new epidemic due to no new antibiotics -**vulnerable groups given flu vaccine annually, no cure**

Question 41

Animal diseases: malaria

Answer 41

-protoctisa(Plasmodium parasite) and spread by the bites of infected mosquitoes as a vector -parasite has a life cycle with 2 hosts(reproduce in female mosquito which lays eggs, then passed into human bloodstream as mosquito feeds off blood) -invades red blood cells, liver(hides inside them) and brain and starts reproducing inside them -can recur and makes people weak and vulnerable to other infections) **no vaccine and limited cures, control vectors i.e insecticides, prevent breeding by taking away water, mosquito nets**

Question 42

Animal diseases: Ring worm

Answer 42

-a fungal disease, different fungi infects different species -affects cattle(grey-white, crusty, infectious, circular areas of skin), dogs, cats and humans -Causes a circular red rash -not damaging but may be itchy and its unsightly **antifungal creams are effective cure**

Question 43

Animal diseases: Athlete's foot

Answer 43

-fungal disease -affects humans -form of ringworm that grows on and digests the warm, most skin between toes -cracking + scaling--} becomes itchy and sore -**antifungal creams are an effective cure**

Question 44

Plant diseases: Tobacco mosaic virus

Answer 44

-virus that infects around 150 species i.e tobacco plants, tomatoes, cucumbers -damages leaves, flowers, fruit--} stunting growth and reducing yields/crop loss -mosiac pattern of light and dark green on leaves, malformation, yellowing leaves(lack of chlorophyll so lack of photosynthesis) -**no cure but can get resistant crop strains, prevented by removing infected plants and washing hands between planting**

Question 45

Plant diseases: Potato/tomato late blight

Answer 45

-caused by protoctist -hyphae(branching filaments of fungi) penetrates host cells, destroying leaves, tubers and fruit **no cure but resistant strains, careful management and chemical treatments can reduce infection risk**

Question 46

Plant diseases: Black sigatoka

Answer 46

-fungus causes a banana disease -attacks and destroys the leaves -hyphae penetrate and digest the cells, turning the leaves black, prevent photosynthesis and growth of the plant -if plants are infected it can cause a 50% reduction in yield -resistant strains are being developed **good husbandry and fungicide treatment can control the spread of the disease but there is no cure**

Question 47

Plant diseases: Ring rot

Answer 47

-bacterial disease -affects potatoes, tomatoes, aubergines -caused by gram positive bacteria -damages leaves, tubers and fruit -can destroy up to 80% of crop and once ring rot infects a field, it cannot be used to grow susceptible crops for 2 years **no cure**

Question 48

Why does direct transmission happen?

Answer 48

-pathogens will damage host tissues directly -combined with host’s reaction produces symptoms - viruses take over the cell’s metabolism - protoctista can take over cells and digest the cell’s content to reproduce - fungi digest living cells and destroy them(pathogenic fungi)

Question 49

Direct transmission of diseases

Answer 49

-direct contact= exchanging bodily fluids, skin to skin contact, faeces transmitted on the hand -inoculation= breaking the skin, animal bites, puncture wound/sharing needles -ingestion= taking in contaminated food or drink

Question 50

Indirect transmission

Answer 50

(pathogen travels from one individual to the next indirectly) -fomites= inanimate objects i.e bedding/socks -droplet infection(inhalation)= pathogen-laden saliva/mucus inhaled can infect i.e flu, TB -vectors= transmits communicable diseases from one host to another i.e mosquitoes transmit malaria, water is a vector for diarrhoeal diseases

Question 51

factors affecting transmission of communicable diseases

Answer 51

-hygiene + overcrowding= i.e bacteria can remain in the air for long periods of time and infect more people -socioeconomic factors= i.e lack of trained healthcare workers/ insufficient public warning -poor nutrition -weak immune system -culture and infrastructure= medical practices can increase transmission -climate change= introduce new vectors/diseases i.e hotter temps introduce malaria

Question 52

Direct transmission in plants

Answer 52

-direct contact of healthy plant with any part of a diseased plant i.e ring rot, TMV, blight, black sigota

Question 53

Indirect transmission in plants

Answer 53

-contaminated soil = new crop take in pathogens/reproductive spores(protoctista+fungi) from previous infected plants in the same soil—> spores can survive composting process so compost can be contaminated -vectors = (bacterial/viral/fungi) spores may be carried on the wind i.e black sigota - water = spores swim in the surface of water on leaves - animals = can carry pathogens/spores from one plant to the next i.e - humans= pathogens/spores transmitted by hands,clothes, farming practices etc

Question 54

Factors affecting the transmission of communicable diseases in plants

Answer 54

-genetic variation= natural susceptibility -overcrowding increases likelihood of contact -poor mineral nutrition reduces resistance of plants -damp, warm conditions increase survival/spread of pathogens and spores -climate change= increased rainfall allow spores to spread in water

Question 55

What is active immunity?

Answer 55

-immune system makes its own antibodies/memory cells after being stimulated by a pathogen -requires exposure to antigens -protection takes a while to develop -long term protection -memory cells are produced

Question 56

What is passive immunity?

Answer 56

-gain immunity from being given antibodies from a different organism, not exposed to antigen -immediate but short term protection -immune system doesn't make antibodies on its own -no memory cells produced -can be natural(occur naturally in the body) or artificial(acquiring antibodies through exposure to antigens)

Question 57

Natural active immunity

Answer 57

-become immune after catching a disease because you have the T and B memory cells so if you meet a pathogen the second time, your immune system recognises the antigen and can immediately destroy the pathogen

Question 58

Natural passive immunity

Answer 58

-immune system of a new-born is not mature and cannot produce antibodies for the first few months - some antibodies cross the placenta from the mother to her foetus inside the uterus -first breast milk formed(colostrum) is very high in antibodies--} gut allows these glycoproteins to pass into blood stream without being digested -lasts until baby produce own antibodies + antibodies from mum are likely to be relevant to pathogens in environment

Question 59

Artificial passive immunity

Answer 59

-antibodies are formed in one individual(i.e animals), extracted then injected into the bloodstream of another individual -temporary but can be live saving for fatal diseases i.e tetanus infected person can be injected with antibodies against tetanus toxin collected from blood donation

Question 60

Artificial active immunity

Answer 60

-become immune after you've been given a vaccination containing a harmful does of antigen

Question 61

What are vaccinations?

Answer 61

-contains an attenuated(weakened) or inactive version of the pathogen whilst still containing its antigens -antigens allow primary immune response to take place so B and T memory cells can be produced -can also contain altered toxin molecules(tetanus), isolated antigens from pathogen(flu vaccine) and genetically engineered antigens(Hepatitis B)

Question 62

How does a vaccination work?

Answer 62

-small amounts of the safe antigen are injected into you blood -primary immune response(cell mediated and humoural response) triggered by the foreign antigens and your body produces antibodies + memory cells(T remember the complimentary receptor to the measles antigen) -if you come into contact with an active pathogen, the secondary immune response can be triggered and you destroy the pathogen rapidly before suffering symptoms -boosters may be needed to increase the time you are immune to a disease

Question 63

What is a disadvantage of taking vaccines orally?

Answer 63

could be broken down by enzymes in the gut or molecules may be too big to be absorbed by blood

Question 64

Epidemics vs Pandemics

Answer 64

-vaccines are used to help prevent both -epidemics= communicable disease spreads rapidly, local/national level -pandemic= same disease spreads rapidly across a number of countries/continents

Question 65

What is herd immunity?

Answer 65

-Epidemics can be prevented if a large percentage of the population is vaccinated(often have to change to remain effective) -even people who haven't been vaccinated are unlikely to get the disease as there is a smaller volume of pathogens to encounter

Question 66

Immunisation vs vaccination

Answer 66

-vaccines are administrating a substance designed to stimulate the immune system whereas immunisation is the process of developing immunisation -V causes I

Question 67

the MMR vaccine

Answer 67

-protects against measles, mumps and rubella -usually given to children at around 1 then again before they start school -contain attenuated versions of MMR

Question 68

the meningitis C vaccine

Answer 68

-protects against the bacteria that causes meningitis C -first given as an injection to babies at 3 months -boosters for 1 year olds and teens

Question 69

Influenza/flu vaccine

Answer 69

-annual vaccine as it changes every year -viruses that causes strain A mutates regularly due its rapid life cycle + reproduction--} surface antigens change and form new strains -memory cells from one strain vaccine cannot recognise other strains with different antigens(immunologically different) -Labs collect samples of different strains and test the effectiveness of various vaccines to predict which one is most effective against current flu virus -vaccine is given to vulnerable people i.e elderly, sick people/ have autoimmune diseases, youth, pregnant women, healthcare workers(exposed to pathogen) -some people are given a vaccine that protects them from a strain in another country to prevent a pandemic

Question 70

Communicable diseases that cannot be prevented with vaccines

Answer 70

-malaria= protoctista Plasmodium that causes malaria spends most its time of their pathogenic life cycle hidden behind the self antigens in erythrocyte host -HIV= human immunodeficiency virus that causes AIDS--} targets and enters macrophages and T helper cells so it has disabled the immune system itself

Question 71

What are autoimmune diseases?

Answer 71

-when an organism's immune system isn't able to recognise self-antigens and treats it as foreign antigens so launches an immune response to attack healthy tissue -around 80 different autoimmune diseases that can cause chronic inflammation/complete breakdown + destruction of healthy tissue -usually chronic(long-term), so can be treated but not cured

Question 72

Potential reasons for autoimmune diseases

Answer 72

-genetic tendencies -immune system responds abnormally to a mild pathogen/normal body microorganism -T reg cells don't work effectively

Question 73

What do immunosuppressant drugs do?

Answer 73

-prevent the immune system from working + may be used as treatments -BUT they deprive the body of natural defences against communicable diseases

Question 74

Autoimmune diseases: Type 1 diabetes

Answer 74

-takes part in the insulin-secreting pancreas -**treated by insulin injections, pancreas transplants, immunosuppressant drugs**

Question 75

Autoimmune diseases: Lupus

Answer 75

-caused by the immune system attacking cells in the connective tissues -damages tissues and causes painful inflammation + can affect skin and joints, as well as organs i.e heart and lungs -causes fatigue -**no cure but can be helped with anti-inflammatory drugs, steroids, immunosuppressants**

Question 76

Autoimmune diseases: Rheumatoid arthritis

Answer 76

-caused by the immune system attacking cells in the joints -causes pain and inflammation especially in hands, wrists, ankles and feet -**no cure, anti-inflammatory drugs, steroids, immunosuppressants, pain relief**

Question 77

innate immunity

Answer 77

-the immune system you are born with -comprises of your barrier defences and basic immune cells

Question 78

adoptive immunity

Answer 78

-immune system you’ve acquired through exposure to pathogens

Question 79

What are antibiotics?

Answer 79

-chemicals that inhibit can kill/inhibit growth of bacteria -used by humans as drug to treat bacterial infections -widespread from mid 20th cent= death rates from infectious bacteria has decreased rapidly

Question 80

Why are antibiotics useful as a drug?

Answer 80

-can target bacterial cells without harming human cells(selective toxicity)

Question 81

Process of antibiotic resistance

Answer 81

-genetic variation in bacteria population -mutations make some bacteria naturally resistant to antibiotic -allele is advantageous because it is better able to survive in host and reproduce/divide -allele passed on to lots of offspring -becomes more common in population overtime

Question 82

Why is antibiotic resistance a problem?

Answer 82

-infected people cannot easily get rid of bacteria with antibiotics -'superbugs' that are resistant to most known antibiotics are becoming more common

Question 83

MRSA

Answer 83

-can be found on the skin/nose of 1 in 3 people -causes serious wound infections and is resistant to several antibiotics i.e meticillin

Question 84

Clostridium difficile

Answer 84

-infects the digestive system(usually causes problems in people who have already been treated with antibiotics) -CF is resistant to harmless bacteria present in digestive system--} produces toxin which causes severe diarrhoea, fever and cramps

Question 85

preventing antibiotic resistance

Answer 85

-developing new antibiotics and modifying existing ones -doctors can reduce use of antibiotics i.e not for minor infections/prescriptions for elderly people, HIV patients -take full course of antibiotics to make sure infection is fully cleared ad all the bacteria have been killed