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AS Biology > Infectious Diseases > Flashcards

Infectious Diseases Flashcards

(72 cards)

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1
Q

What is a disease?

A

A disease IMPAIRS normal functioning of an organism, leading to poor health

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2
Q

What is an INFECTIOUS disease

A

A disease that is caused by pathogens and can be passed on between individuals

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3
Q

What is a non infectious disease

A

A disease that is not caused by pathogens and cannot be passed between people

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4
Q

What is an infectious disease key phrases

A

Transmissible
Passed on from infected organism to uninfected organism
Caused by pathogen (eg HIV causes AIDS, Mycobacterium tuberculosis causes TB)
Caused by virus, bacterium, fungus, protoctist

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5
Q

Examples of non infectious disease

A

Sickle cell anaemia
Coronary heart disease (CHD)
Emphysema

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6
Q

What type of pathogen causes Cholera

A

Bacterium

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7
Q

What bacterium causes Cholera

A

Vibrio Cholerae

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8
Q

How is cholera transmitted

A

FECAL-ORAL route
1. Enters body in contaminated food and water
2. Bacteria breeds in SMALL INTESTINE and secretes CHOLERAGEN (choleragen enters by endocytosis)
3. Choleragen reduces the ability of the epithelium of the intestine to absorb salts and water in the blood —> increased conc of salts in blood —> higher water potential gradient
4. These are lost in the faeces causing diarrhoea, if not treated loss of fluid can be fatal

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9
Q

Treatment of cholera

A

Oral rehydration therapy (ORT) - solution of salts and glucose to hydrate the body
Make sure FLUID INTAKE = FLUID LOSSES in the urine and faeces to maintain OSMOTIC balance of blood and tissue fluids
Take ANTIBIOTICS

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10
Q

Prevention and control of cholera

A

Transmission most likely to occur in CROWDED and IMPOVERISHED condition —> REFUGEE CAMPS
Improper access to proper sanitation, a clean water supply and uncontaminated food
Best controlled by treating sewage effectively, providing a clean water supply and maintaining good hygiene in food preparation
No fully effective vaccine against cholera —> intestinal cells ANTIGENIC CONCEALMENT, antibodies cannot reach intestines

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11
Q

Mode of action of cholera

A

Bacteria bypasses stomach and enters lumen of small intestine
Enters intestinal cells by endocystosis, choleragen released
Choleragen inhibits protein channels, salts/ions canot enter bloodstream
High conc of ions —> low water potential in intestine
Water enters by osmosis —> diarrhoea

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12
Q

Global distribution of cholera

A

West and East Africa, Afghanistan
Unknown in MEDC’s due to sewage treatment and cleaned piped water
Transmission cycle broken

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13
Q

Explain how it is possible to reduce the number of deaths during a cholera epidemic

A

Provide boiled water to kill bacteria
Provide ORT containing electrolytes and salts
Absorption of salts helps absorbs glucose
Absorption of salts increases water uptake by osmosis
Deaths usually caused by rapid dehydration
Rapid provision of medical supplies
For severe cases antibiotics should be taken
Safe sewage disposal

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14
Q

Explain why cholera is unlikely to be transmitted in developed countries

A

Transmission cycle broken
Sewage treatment plans, mains drainage
Human faeces does not come in contact with drinking water supply
Water treatment plants
Drinking water is piped to homes

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15
Q

Explain why cholera is likely to be transmitted in underdeveloped countries

A

Greater exposure to contaminated water and food supply
No safe drinking water sources
Lack of hygiene
Faeces and sewage mixed with drinking water
Insufficient access to oral cholera vaccines
Lack of education
Differences in effectiveness of surveillance and reporting
Refugee camps
Increase in antibiotic resistance
Lack of health services
Inadequate access to healthcare and medicine

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16
Q

Explain how cholera bacteria are transmitted from one person to another

A

Fecal oral route
Bacteria leaves infected person in faeces
Bacteria enters water supply
Bacteria ingested by uninfected person

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17
Q

Discuss the problems involved in preventing the spread of cholera

A

Poor sanitation, no treatment of faecal waste
Contaminated of drinking water supply
Poverty, poor living conditions
Poor hygiene
Lack of education about transmission and health
Refugee camps
Lack of water purification
No rehydration therapy available
No effective vaccine

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18
Q

What type of pathogen cause Malaria

A

Protoctist

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19
Q

What protoctist causes malaria

A

Plasmodium

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20
Q

What are the 4 species of plasmodium

A

Plasmodium FALCIPARUM
Plasmodium MALARIAE
Plasmodium OVALE
Plasmodium VIVAX

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21
Q

How is malaria transmitted

A

Mosquito acts as a VECTOR for malaria
Female anopheles mosquito containing plasmodium in salvia feeds on human blood
When a mosquito bites an infected person, plasmodium is taken up into the mosquitos body and eventually reaches its salivary glands

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22
Q

How can malaria be prevented?

A

Reducing the population of mosquitos: removing sources of water in which the can be, releasing large numbers of sterile males

Preventing mosquito bites: mosquito nets, dark clothing, long sleeved clothes, repellent

Prophylactic drugs- drugs that prevent pathogens from breeding (quinine and chloroquine, mefloquine, proguanil)

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23
Q

Where is malaria prevalent?

A

Topical and subtropical regions- where humidity is high

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24
Q

Reasons for worldwide concern over the spread of malaria

A

Increase in drug resistant forms of plasmodium
Difficulties in developing a vaccine
Change in climate and environmental changes that favour the spread of mosquitos
Migration of people

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25
What is the relevance of anticoagulants in malaria?
Anticoagulant in saliva is passed when mosquito feeds/takes a blood meal anticoagulant prevents blood clotting when the mosquito sucks blood
26
Discuss the factors that determine the distribution of malaria worldwide
Tropics, subtropic Areas: Africa, Central America, South America, South Asia Countries: India, Sri Lanka, china, Vietnam, Naya Areas where both parasite and anopheles are present Anopheles survive in hot humid areas Parasite needs to reproduce within he mosquito Poor health facilities Mosquitoes resistant to repellent Parasite resistant to prophylactic drugs High population density —> lots of mosquitos Human activity —> breeding sites for anopheles
27
Describe how malaria is passed from an infected person to an uninfected person
Female anopheles mosquito takes BLOOD MEAL from an infected person and feeds on uninfected person Plasmodium transmitted in mosquitos saliva Blood transfusion
28
Unlike malaria, TB is found across the whole world, explain the distribution pattern
Anopheles mosquito survives within the tropics Plasmodium needs to reproduce within the mosquito Eradicated in some countries outside the tropics LEDCs do not have mosquito control programmes Mosquitos resistant to insecticides or repellents Plasmodium resistant to prophylactic drugs eg chloroquine TB is airborne and is transmitted through water droplets Does not require a vector
29
Describe one method of controlling the spread of malaria by targeting its vector and explain its effect
Elimination of free standing water Removes mosquito breeding sites Use insecticides Kills adult mosquitos
30
Explain why it has been difficult to develop an effective vaccine for malaria
Plasmodium has many antigens Many different stages of life cycle More than one plasmodium species Different stages of life cycle Mutation changes antigens due to antigenic shift/drift Parasite only vulnerable at certain stages of life cycle Antigenic concealment
31
Type of pathogen that causes TB
Bacterium
32
What is the bacterium that causes TB called?
Mycobacterium tuberculosis, mycobacterium bovis (rarely)
33
How is TB transmitted?
M.tuberculosis can enter lungs in airborne droplets of liquid that are breathed in M.bovis is the causative form of TB in cattle
34
Prevention and control of TB
Chest x ray and sputum test Increasing standards of living BCG vaccine Treatment of HIV by drug therapy reduces the risk that an HIV positive person will get TB Drugs- isoniazid and rifampicin
35
TB cannot always be cured with antibiotics because
Many strains of M.tuberculosis bacterium that have evolved resistance to most of the antibiotics that are used The bacteria reproduce inside body cells, where it is difficult for drugs to reach them Drugs need to be taken over a long period
36
Describe the global distribution of TB
Both high income and low income countries Poor housing in inner cities in the developed world and rising homelessness Breakdown of TB control programs Increased migration Refugee camps
37
Suggest why fatality ratios of TB are higher in some of countries than in others
Overcrowded housing Not diagnosed early enough DOTS- direct observation treatment short course Lack of vaccination Antibacterial drugs not available Medical services not available TB lined to HIV/AIDS Not completing antibiotic treatment course No facilities for isolating people
38
Discuss the problem to be faced in the eradication of TB
Tb found worldwide High incidence in developing countries (LEDCs) Problem with vaccine (BCG) —> does not work well for all ethnic groups etc Difficult to identify infected people Difficulty with contact tracing Difficult to diagnose
39
Explain why the antibiotics used to treat TB are taken in combination over a long period of time
Bacteria likely to be resistant to at least one antibiotic Less likely to be resistant to all Antibiotics used is very small Change/mutation in DNA Bacteria are inside cells, protected from antibiotics Mycobacteria divide slowly Ensures all bacteria killed Bacteria remains Prevents development of antibiotic resistance
40
What type of pathogen causes AIDS
Virus
41
What is the name of the virus that causes AIDS
HIV- human immunodeficiency virus
42
What is HIV, what is its structure?
Retrovirus, contains RNA Protein core contains 2 RNA molecules Retrovirus- uses RNA to produce a single strand of DNA inside the host cell, using reverse transcriptase
43
How is HIV transmitted
Infected blood from one person entering another (sharing hypodermic needles) Exchange of fluids from penis, vagina or anus —> sexual contact Transmission across placenta from mother to foetus or in breast milk Promiscuous sex
44
Mode of action of HIV
HIV attaches to receptors on T-helper cells Viral RNA fuses with T-helper cell Viral RNA acts as a template to male a single strand of DNA (cDNA) by using reverse transcriptase Viral DNA formed Viral DNA inserts itself into chromosomal DNA of the host cell —> provirus Viral DNA transcribed into mRNA New viruses are made from the protein and RNA Infected T cell bursts open to release new viruses, destroying it which infects other host cells Role of T-helper cells is eventually reduced or not carried out Macrophages and T killer cells are not activated B cells not activated, fewer antibodies produced Cytokines not released Immune system weakened and compromised
45
When is HIV considered AIDS
When CD4 cell count is below 200
46
How can HIV be prevented and controlled?
Blood transfusions screened Hypodermic needles should be sterile and only used once, disposed safely Contact tracing, sexual contact traced Contraception Less promiscuous sex Education programs
47
Why is there no vaccine available for HIV/AIDS
Virus mutates rapidly- antigens on viral coat keep changing Harder for immune system to recognise the virus
48
What is the global distribution of HIV/AIDS
Global, increasing worldwide Most prevalent in sub Saharan Africa (Gambia think Geo)
49
Medicine available for HIV/AIDS
No treatments, virus mutates rapidly so antigens on viral coat keeps changing Drugs available to help with symptoms and prolong life Zidovudine, similar to nucleotide thymine —> binds to reverse transcriptase blocks it’s action
50
Suggest how HIV infection may have led to an increase in malarial infections
HIV infects T cells Both contracted through blood transfusion
51
List two factors in the prevention and control of HIV/AIDS that would help improve average life expectancy in African countries
Education to prevent transmission Anti HIV drug therapy Access to contraception Avoid promiscuity HIV positive mothers avoid breast feeding Screening before blood transfusion Needle exchange schemes
52
What type of pathogen causes small pox
Virus
53
What virus causes small pox
Variola virus
54
How is small pox transmitted
Airborne- inhalation of droplets of moisture containing the virus
55
Prevention and control of small pox
Eradicated by vaccine programme coordinated by WHO
56
What kind of pathogen causes measles
Virus
57
What virus causes measles
Morbillivirus
58
How is measles transmitted
Airborne- inhalation of droplets of moisture donating the virus
59
How can measles be prevented and controlled?
Vaccination, two doses If infected, prevent close contact —> isolation
60
What is an antibiotic
Substance that kills bacteria without harming human cells
61
What is the mode of action of penicillin
When new bacterial cells grow it secretes autolysins which create small holes in cell wall —> allows cell wall to stretch and create cross links Penicillin inhibits glycoprotein peptidase enzymes by blocking or altering the shape of the active site This prevents the synthesis of links between peptidoglycan molecules in bacterial cell walls, cross links cannot form Bacteria takes up water by osmosis which causes cell lysis
62
How do antibiotics work
By interfering with the growth or metabolism of the target bacterium Eg. Synthesis of bacterial cell walls, activity of proteins in bacterial cell surface membranes, bacterial enzyme action, bacterial DNA synthesis
63
Why do antibiotics not affect viruses?
No cell wall When a virus replicates, it uses the host cell’s mechanisms for transcription and translation —> antibiotics cannot bind to host cell proteins
64
Why are some antibiotics ineffective against bacteria
Thick cell wall rescues permeability Some enzymes break down penicillin
65
Development of resistance to penicillin
Natural selection Use of penicillin produces SELECTIVE PRESSURE against bacteria causing mutations to occur Causes bacteria to have GENETIC VARIATION —> new alleles of genes Gene produced is resistant to penicillin and is found in plasmids of bacteria Penicillin resistant gene codes for production of b lactamase, enzyme which breaks down penicillin Survive and reproduce Pass on their advantages allele to next generation Higher proportion of bacteria is resistant
66
How can antibiotic resistance be reduced?
Use antibiotics only when necessary, not for viral infections Course needs to be complete Change the type of antibiotic prescribed Avoid wide spectrum antibiotics Minimise use in agriculture
67
What is vertical transmission
Bacteria reproduce asexually by binary fission One bacterium contains mutant gene, proving antibiotic resistance to other generations
68
Horizontal transmission
Plasmids contain antibiotic resistant genes Plasmids transferred between bacteria Conjugation occurs- thin tube forms between two bacteria to allow exchange of DNA
69
Why does antibiotic resistance occur?
Overuse of antibiotics Incorrect use of antibiotics Eg- treatment for non serious infection
70
What is a consequence of antibiotic resistance?
Reduced effectiveness of antibiotics Increase in incidence of antibiotic resistance
71
Suggest two ways streptomycin acts as ribosomes to inhibit protein synthesis
Binding of tRNA prevented No anticodon, codon bringing Peptide bond not formed mRNA attachment prevented Inhibition of enzymes involved in translation Ribosome movement along mRNA hindered Inhibits association of large and small subunits
72
Suggest why streptomycin does not harm mammalian cells
Cell surface membrane impermeable Degraded before entry into cell Broken down m enzymes Eukaryotic, 80S ribosomes- different ribosome structure

AS Biology (5 decks)

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