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A-level Biology > Infectious Diseases > Flashcards

Infectious Diseases Flashcards

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1
Q

What is a disease

A

An abnormal function of the body
- condition that impairs the normal functioning of an organism, leading to poor health
- each disease is associated with a set of symptoms
- infectious/non-infectious

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2
Q

Infectious diseases

A

• transmissible / communicable / contagious / transferable

• passed from one (infected) person / host / organism, to another

• caused by a pathogen / microorganisms / (x2) virus / bacterium / fungus / protoctist / worm

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3
Q

Modes of transmission of infectious diseases

A

• direct contact (if pathogen cannot survive outside the body)
• water
• food
• faeces
• animals e.g. insects
• indirectly from person to person
• symptomless carriers (spread pathogen even if don’t have disease)

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4
Q

Pathogen def
Examples

A

Organism that causes disease
e.g. virus, bacterium, fungi, protoctists

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5
Q

Examples of pathogens that cause diseases

A

• HIV —> virus that causes AIDS

• Mycobacterium tuberculosis —> bacterium that causes TB

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6
Q

Parasite

A

Organism that live on/in another organism (host) and causes damage to that organism

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7
Q

Some parasites can cause …

A

Disease
Therefore is a pathogen

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8
Q

Example of pathogen that can cause disease

A

Plasmodium species —> single-called parasite that causes malaria

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9
Q

Examples of infectious diseases

A

• cholera

• malaria

• HIV/AIDS

• tuberculosis (TB)

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10
Q

Causes of malaria

A

• by a protoctist / Plasmodium

• several different species - cause different types of malaria

• Plasmodium infects RBC and breeds inside them

• toxins released when Plasmodium bursts out of cell - causes fever

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11
Q

…

A
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12
Q

Key phrases - Malaria causes

A

• Plasmodium / falciparum / malariae / ovale / vivacité

• (only) female feeds on blood

• female requires blood (protein) for (development of) eggs

• (only) female carries pathogen / disease-causing organism / Plasmodium / parasite

• (only) female transmits the disease

• (only) female is vector

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13
Q

…

A
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14
Q

Transmission of Malaria

A
  1. Female Anopheles mosquito feeds on human blood to obtain the protein needed to develop they eggs
  2. If the person they bite is infected with Plasmodium, they will take up some of the pathogen’s gametes with the blood meal
  3. Gametes fuse and develop in mosquito’s gut to form the infective stages
  4. Infective stages move to the mosquito’s salivary glands
  5. When mosquito feeds again, it injects the anticoagulant that prevents blood meal from clotting so it flows out of host into the mosquito
  6. The infective stages pass out into the blood
    together with the anticoagulant in the saliva
  7. parasite enters the hepatocytes (liver cells) where they mature and multiply
  8. burst out of the hépatite and enter the RBCs, where they multiply
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15
Q

Prevention and control

A

• remove population of mosquitos

• prevent mosquitos biting people

• use Prophylactic drugs

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16
Q

Methods to remove population of mosquitos

A

• remove sources of water

• layer of oil on water

• stock ponds, irrigation and drainage ditches and other forms fo water, with fish

• spray a bacterium

17
Q

Methods to prevent mosquitos biting people

A

• sleep under mosquito net soaked in insect repellent every 6 months

• wear long sleeves - especially at dusk

• insect repellent - some resistant to DDT and other insecticides

18
Q

Drugs used to prevent malaria

A

Prophylactic drugs - prevent infection and breeding in a person
- take drug before, during and after visiting an area with high cases of Malaria

• chloroquine - inhibits protein synthesis and prevents parasite spreading inside the body

• proguanil - inhibits sexual reproduction of Plasmodium inside the biting mosquito (stops gametes fusing in gut)

19
Q

Name and type of pathogen that causes cholera

A

Vibrio cholerae / V. Cholerae

Bacterium

20
Q

Name and type of pathogen that causes Malaria

A

Plasmodium - malariae, falciparum, ovale, vivax

Protoctist

21
Q

Name and type of pathogen that causes tuberculosis (TB)

A

Mycobacterium tuberculosis / Mycobacterium bovis

Bacterium

22
Q

Name of pathogen that causes HIV/AIDS

A

Human Immunodeficiency Virus (HIV)

23
Q

Transmission of cholera

A

Contaminated food and water
E.g. water/food in contact with untreated sewage

24
Q

Transmission of malaria

A

• Female anopheles mosquito
• Blood transfusion and re-use of unsterile needles
• Mother to child across placenta

25
Q

Transmission of TB

A

• airborne - infected people cough/sneeze
—> Mycobacterium tuberculosis bacteria enter the air in tiny droplets of liquid
—> uninflected people inhale
—> spread faster in overcrowded conditions

• Mycobacterium bovis occurs in cattle - spread to human through contaminated meat and unpasteurised milk

26
Q

Transmission of HIV/AIDS

A

• retrovirus
• sexual contact
• infected blood / contaminated needles - e.g. IV drug users using the same needle
• mother to foetus in early stages of pregnancy, birth or breastfeeding
• promiscuous sex
—> mucus lining of rectum not as thick as vagina
—> less natural lubrication
—> damage occurs more easily during intercourse
—> virus pass from semen to blood

27
Q

Retrovirus

A

Virus with the ability to make DNA from RNA because they have reverse transcriptase

28
Q

Infectious diseases are caused by

A

Pathogens

29
Q

Small pox pathogen

A

Variole virus

30
Q

Small pox transmission

A

Inhalation of droplets of moisture containing the virus

31
Q

Prevention and control of smallpox

A

Eradicated by a vaccination programme coordinated by WHO

32
Q

Mode of action of penicillin

A

• penicillin inhibits a group of enzymes (glycoprotein peptidases) by blocking or altering the shape of the active site

• enzymes used by bacteria to form cross-links between the peptidoglycan molecules that make the cell walls
—> so, penicillin causes the peptidoglycan chains to not link up and stops cross-links from forming

• when a newly formed bacterial cell is growing, it secretes enzymes (antolysins), which make little holes in the cell wall
—> alone wall to stretch so a new reptidoghycan chain can link

• when penicillin present, cross-links can’t form, cell wall not made, but autolysins Keep making new holes

• bacteria takes up water by osmosis and the cell swells which then bursts due to the weakened cell wall which can’t withstand the increased pressure as the turgar of cells not resisted by cell walls

• penicillin doesn’t harm viruses or human cells
—> don’t have cell walls and don’t contain peptidoglycans
—> don’t have peptidase or cytoplasm

A-level Biology (10 decks)

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