Unit 3 - Infection & Response Flashcards

1
Q

What is a communicable disease?

A

A disease caused by a pathogen which can
be passed between animals or plants eg. flu.

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2
Q

What is a pathogen?

A

A disease-causing microorganism e.g.
bacteria

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3
Q

How do bacteria cause disease?

A

Once inside the body, they divide rapidly by
binary fission. They kill cells and produce
harmful toxins.

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4
Q

How do viruses cause disease?

A

They invade and reproduce inside living
body cells, leading to cell damage.

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5
Q

Give three ways in which pathogens can be spread

A

● By air - flu, tuberculosis and the common cold are
spread by droplet infection.
● By water - fungal spores in water spread plant
diseases.
● By direct contact - common in plant diseases and
sexually transmitted infections.

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6
Q

Give four ways in which the spread of pathogens
can be reduced

A

● Hygiene - handwashing, disinfectants, tissues.
● Reducing contact with infected individuals -
quarantine.
● Removing vectors - use of pesticides and
insecticides, removal of habitats.
● Vaccination.

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7
Q

Why is it especially important to prevent the spread
of viral diseases?

A

Scientists have not yet developed cures for
many viral diseases.

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8
Q

What is measles?

A

Measles is a serious viral disease that can
cause blindness and brain damage. The
main symptoms are a fever and a red skin
rash.

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9
Q

How is measles spread?

A

By air - through the inhalation of droplets
from coughs and sneezes

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10
Q

What is HIV/AIDS?

A

HIV is a virus which attacks and damages the
immune system until it can no longer function
properly. AIDS is the condition resulting from a
long-term HIV infection. There is no cure or
vaccine for HIV/AIDS.

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11
Q

How is HIV spread?

A

Direct sexual contact and the exchange
of bodily fluids eg. blood, breastmilk.

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12
Q

How can the spread of HIV/AIDS be prevented?

A

● Use of condoms
● Screening of blood for transfusions
● Not sharing needles
● Bottle-feeding by HIV-positive mothers
● Use of antiretroviral drugs to prevent the
development of AIDS

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13
Q

What is tobacco mosaic virus?

A

A plant pathogen which causes leaf discolouration
when cells are damaged. Affected areas cannot
photosynthesise, reducing the crop yield. As there is
no treatment, farmers grow TMV-resistant crop
strains to avoid infection.

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14
Q

How is tobacco mosaic virus spread?

A

Contact between infected and healthy plants.
Insects may act as vectors which transfer the
virus between different plants.

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15
Q

What is salmonella?

A

A type of bacteria found in raw meat, poultry
and eggs. If they enter the body via food
poisoning, they can affect natural gut
bacteria.

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16
Q

What are the symptoms of salmonella food poisoning?

A

● Fever
● Abdominal cramping
● Vomiting
● Diarrhoea
May be fatal in very young or elderly populations due the
risk of dehydration.

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17
Q

How can the spread of salmonella be limited?

A

● Vaccinating animals intended for consumption
● Keep raw meat away from cooked meat
● Disinfect hands and surfaces after contact with
raw meat
● Thoroughly cook meat

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18
Q

What is gonorrhoea?

A

A sexually transmitted bacterial infection caused by
unprotected sex with an infected individual. Early symptoms
include yellow/green discharge from genitals and painful
urination, although it may be symptomless.
Its spread can be controlled through the use of antibiotics (no
longer penicillin as many strains are resistant) and using
condoms.

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19
Q

What is rose black spot?

A

A fungal disease which causes purple or black
spots to develop on rose leaves. It reduces the
area of the leaf which is available for
photosynthesis and causes leaves to turn yellow
and drop prematurely.

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20
Q

How is the rose black spot fungus spread?

A

Fungal spores are spread by the wind
and in water.

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21
Q

How can the rose black spot fungus be treated?

A

● Using fungicides
● Destroying infected leaves

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22
Q

What is malaria?

A

Malaria is a disease caused by protist pathogens.
The disease is carried from host to host by
mosquitoes, and the protists enter the human
bloodstream when they feed. Symptoms include
fever and shaking, and it may also be fatal in some
cases.

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23
Q

How can the spread of malaria be reduced?

A

● Using insecticides
● Using insect nets to avoid bites
● Prevent mosquito breeding by removing stagnant
water
● Antimalarial drugs

24
Q

How does the skin prevent pathogens from entering
the body?

A

● Acts as a physical barrier.
● Scab formation after skin is cut/wounded.
● Antimicrobial secretions which can kill pathogens.
● Healthy skin flora compete with pathogens and
act as an additional barrier.

25
How does the respiratory system prevent pathogens from entering the body?
● Nose - has hairs and mucus which trap pathogens. ● Trachea and bronchi - have mucus that traps pathogens. Ciliated cells move mucus to the mouth so it can be swallowed.
26
How does the stomach prevent pathogens infecting the body?
● Secretes hydrochloric acid - kills any pathogens present.
27
How does phagocytosis protect us against disease?
White blood cells (phagocytes) ingest and destroy pathogens so they cannot infect more cells.
28
How does antibody production protect us against disease?
White blood cells produce antibodies which are complementary to a specific antigen on a pathogen. The binding of antibodies to antigens causes pathogens to clump together, making them easier to destroy. In the case of a second infection, the correct antibodies can be produced rapidly, preventing the person getting the same disease again.
29
How does antitoxin production protect us against disease?
Antitoxins bind to toxins released by pathogens and neutralise them.
30
What is a vaccination?
Contains a dead or inactivated form of the pathogen which stimulates white blood cells to produce complementary antibodies to the pathogen. In the case of a second infection, memory cells can rapidly produce the correct antibodies and prevent illness.
31
What is herd immunity?
If a sufficiently high proportion of a population are immune to a disease (especially through vaccination), the spread of this disease will be limited.
32
What are the advantages of vaccinations?
● They have eradicated many deadly diseases eg. smallpox. ● Many epidemics can be prevented by vaccinations. ● Herd immunity protects those who cannot have vaccinations.
33
What are the disadvantages of vaccinations?
● Not guaranteed to work - might not protect against multiple strains of a pathogen. ● May be side effects or adverse reactions.
34
What drugs are used to cure some bacterial diseases?
Antibiotics - they can kill bacterial pathogens inside the body.
35
How do antibiotics work?
Antibiotics eg. penicillin kill bacterial pathogens inside the body, but do not kill human cells. Whilst some antibiotics kill a wide range of bacteria, it is important that the right antibiotic is used for specific bacteria.
36
Why can antibiotics not be used to treat viral diseases?
Antibiotics have no effect on viral pathogens as they live inside the host’s (human) cells. Therefore, it is difficult to design drugs that would kill the virus and not destroy human cells at the same time.
37
What is antibiotic resistance?
Antibiotic resistance occurs when mutations lead to individual bacteria being resistant to an antibiotic. These bacteria are able to survive, reproduce and pass on their alleles, leading to a greater proportion of antibiotic-resistant bacteria. This is concerning as some types of bacteria are becoming resistant to all known antibiotics, so the diseases that they cause cannot be cured.
38
How can we prevent antibiotic resistance?
● Avoid overuse and unnecessary use of antibiotics - eg. antibiotics are often used for viral infections. ● Finish antibiotic courses - to ensure all bacteria is killed.
39
What effect do painkillers have on infectious diseases?
Painkillers can only treat the symptoms but do not kill pathogens.
40
What plant is the heart drug digitalis extracted from?
Foxgloves
41
What painkiller originates from a compound found in willow bark?
Aspirin
42
What antibiotic was discovered by Alexander Fleming from a type of mould?
Penicillin
43
What are the four qualities of a good medicine?
● Effective ● Safe ● Stable ● Able to be taken in and removed easily
44
What three main factors are tested for when developing new drugs?
● Toxicity ● Efficacy ● Dose
45
How is preclinical testing carried out?
In a laboratory - uses cells, tissues and live animals
46
How is clinical testing carried out?
Uses healthy volunteers and patients. Firstly, the drug is tested at a low dose on healthy people - then tested on patients and on a larger scale to find the optimum dose. Often, one group receive a placebo (not the test drug) and the other group receive the actual drug, in order to assess its efficacy.
47
What is the difference between a single-blind and a double-blind trial?
In a single-blind trial, only the doctor knows whether the patient is receiving the drug or the placebo. In a double-blind trial, neither the patient nor the doctor knows. Double-blind trials help remove bias on the part of the doctor.
48
What is a peer review?
Where the results of drug trials are checked over by scientists knowledgeable in this field.
49
How do aphids cause damage to plants?
They use their sharp mouthparts to extract sap from the plant phloem, weakening the plant. They are also vectors who can transfer pathogens from diseased plants to healthy plants
50
How can we reduce the number of aphids?
● Chemical pesticides ● Biological pest control - using ladybirds
51
Why do plants need a good supply of magnesium ions?
Magnesium ions are required to synthesise chlorophyll, which absorbs light energy during photosynthesis. As a result, the leaves cannot photosynthesise properly and they turn yellow (chlorosis).
51
Why do plants need a good supply of nitrate ions?
Nitrate ions are required to convert sugars into proteins which are required for the plant to grow. As a result, the growth of the plant will be stunted if there is not an adequate supply of nitrates
52
What are the symptoms of disease in plants?
● Stunted growth (lack of nitrate ions) ● Spotted leaves (eg. rose black spot fungus) ● Decay/rotting ● Growths ● Malformation of stems/leaves ● Discolouration ● Presence of pests
53
What are three ways in which plant disease can be identified?
● Reference to a gardening website or manual ● Laboratory testing ● Monoclonal antibody test kits
54
Give examples of physical defence responses used by plants
● Cellulose cell walls ● Tough waxy cuticle on leaves ● Outside layer on stems/bark on trees ● Leaf fall
55
Give examples of chemical defence responses used by plants
● Antibacterial chemicals ● Poisons
56
Give examples of mechanical defence responses used by plants
● Thorns and hairs to deter animals ● Leaves that droop/curl on contact ● Mimicry to trick animals