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Y4 Biology > 10. Infectious Diseases > Flashcards

10. Infectious Diseases Flashcards

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1
Q

Infectious Diseases

Definition + Examples

A

Infectious diseases can be transmitted from person to person, and are caused by disease-causing microorganisms called pathogens, which include bacteria and viruses.

Examples:

  • Bacteria: Pneumococcal disease, syphilis, tuberculosis
  • Viruses: Infeluenza, common cold, HIV, Covid-19
  • Fungi: Athlete’s foot, ringworm
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2
Q

Non-infectious Diseases

Definition + Examples

A

Non-infectious diseases cannot be transmitted from person to person, and are not caused by pathogens.

Examples:

  • Liver cirrhosis (caused by excessive alcohol consumption)
  • Coronary heart disease (caused by excessive fat consumption and smoking)
  • Type 2 diabetes
  • Sickle cell anaemia
  • Asthma
  • Allergies
  • Atherosclerosis
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3
Q

Ways that Infectious Diseases Spread

A
  1. Through droplets in the air:
  • When an infected person coughs or sneezes, they expel respiratory droplets, which may contain pathogens that are breathed into the respiratory tract of an uninfected person
  1. By coming into contact with body fluid of an infected person
  • STIs: exchange of body fluids during sexual intercourse
  • Breastfeeding from mother to child
  • Mucous membrane lining eyes, nose or mouth coming into contact with fluids (blood) of an infected person
  1. By contaminated food and water
  • When food and water are not properly handled or stored, or when there is a lack of clean water supply
  • E.g. Cholera is a water-borne disease
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4
Q

Bacteria

Characteristics

A

Bacteria are mostly unicellular organisms

  1. Larger than viruses, about 0.1mm in length, visible under a light microscope.
  2. No nucleus or other membrane-bounded organelles.
  3. Has a cell membrane, cytoplasm and ribosomes.
  4. Has a bacterial cell wall which is primarily made of peptidoglycan (composed of sugars and amino acids) and proteins.
  5. Has genetic material which consists of a circular chromosome consisting of a coiled-up, circular strand of DNA.
  6. May have smaller rings of DNA called plasmids.
  7. Some motile bacteria possess long thread-like structures called flagella which allow them to move, either toward or away from certain stimuli.
  8. Some bacteria have a slime capsule, which is a sticky layer of polysaccharide or protein that can help cell adherance and/or evasion of a host’s immune system.
  9. Some are pathogenic (disease causing) and some are non-pathogenic (non-diseases causing).
  10. Antibiotics are used to kill or inhibit the growth and replication of bacteria.
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5
Q

Bacterial Cell Wall vs Plant Cell Wall

A

Bacteria cell wall is primarily made of peptidoglycan (composed of sugars and amino acids) and proteins.
Plant cell wall is made of cellulose fibres embedded in a polysaccharide matrix.

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6
Q

Transmission of Diseases Caused by Bacteria

A

Diseases caused by bacteria can be transmitted through:

  1. Droplets in air when an infected person coughs or sneezes (tuberculosis)
  2. Sexual contact (gonorrhoea and syphilis)
  3. Contaminated food and water (cholera)
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7
Q

Viruses

Characteristics

A

Viruses are the smallest disease-causing particles known

  1. Visible only under an electron microscope (at magnifications of about x3000)
  2. Always made up of genetic material (either DNA of RNA) surrounded by a protein coat known as the capsid.
  3. Some viruses are surrounded by an envelope that is derived from the host cell’s membrane.
  4. No cellular structures like cell wall, cell membrane, cytoplasm, organelles or ribosomes.
  5. Viruses usually infect specific cell types. Some infect bacteria only, or plant cells only, or animal cells only, or fungi only.
  6. They vary in shape.
  7. Some viruses have spike proteins on their surface.
  8. Antibiotics have no effect on viruses.
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8
Q

Mode of Life for Viruses

A

Viruses are incapable of carrying out any normal living processes outside a living cell (does not grow, move, feed, respire or excrete).

Viruses are biochemical parasites as they take control of a living cell, known as the host cell. They require a living host cell to reproduce using the cell’s enzymes and organelles like ribosomes.

The first step involves getting the genetic material of the virus, together with viral proteins, across the cell membrane of the host cell into the cytoplasm.

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9
Q

Influenza

What it is + Structure

A

Influenza or flu is a disease that attacks the respiratory system.
There are three main types of influenza viruses responsible for influenza infections in humans: Type A, Type B and Type C. They are quite similar in structure.

Structure: Genetic material, capsid, envelope, spikes proteins.

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10
Q

Transmission of Influenza

A

Influenza is transmitted from person to person

  1. Through droplets in the air by coughing or sneezing.
  2. By coming into contact with contaminated surfaces then eyes, nose, or mouth.

Adults may be contagious from one day before the onset of symptoms till 5 to 7 days after onset.
Children and persons with weakened immune systems may be infectious for longer periods of time.

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11
Q

Methods to Reduce Transmission of Influenza

A

Antibiotics have no effect on viruses.

  1. Annual influenza vaccination.

Other measures include:

  1. Practising good personal hygiene. Wash hands regularly and thoroughly with soap and water.
  2. Turning quickly away from anyone and cover your nose and mouth when coughing and sneezing.
  3. Avoid crowded places if you are unwell.
  4. Staying home from work or school when you are sick.
  5. Using a serving spoon when sharing food.
  6. Wear a mask when you are having a flu.
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12
Q

Pneumococcal Disease

What it is

A

Pneumococcal disease is caused by a bacterium called Streptococcus pneumonia, also known as pneumococcus. There are more than 90 types of this bacterium.

Pneuomococcus can attack different parts of the body and cause serious infection of:

  • Lungs (pneumonia)
  • Blood (bacteraemia)
  • Coverings of the brain and spinal cord (meningitis)
  • Middle ear (acute otitis media)
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13
Q

Transmission of Pneumococcus

A

Pneumococcus is transmitted from person to person

  1. Through droplets in the air by coughing or sneezing.
  2. By coming into contact with contaminated surfaces then eyes, nose, or mouth.

Not everyone exposed to the bacteria develops the disease. Some people become carriers, while others progess to develop the infection.

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14
Q

Signs and Symptoms of Pneumococcal Diseases

A

Signs and Symptoms of Pneumococcal Diseases

  1. Fever
  2. Headache
  3. Vomiting
  4. Cough
  5. Chest pain
  6. Rapid breathing
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15
Q

Methods to Reduce Transmission of Pneumococcus Bacteria

A
  1. Get the pneumococcal vaccination.

Other measures include:

  1. Practising good personal hygiene. Wash hands regularly and thoroughly with soap and water.
  2. Turning quickly away from anyone and cover your nose and mouth when coughing and sneezing.
  3. Avoid crowded places if you are unwell.
  4. Staying home from work or school when you are sick.
  5. Using a serving spoon when sharing food.
  6. Wear a mask when you are having a flu.
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16
Q

Treatment for Pneumococcal Disease

A

Prompt treatment with antibiotics, such as penicillin, is usually effective.

However, in recent years, treatment has become more challenging with the emergence of strains resistant to antibiotics, especiallly penicillin.
Patients infected with such strains will require a longer hospital stay and alternative therapy.

17
Q

Antibiotics

Definition

A

Antibiotics are substances that kill or inhibit the growth and replication of bacteria.

18
Q

How Antibiotics Work

A

Some antibiotics are highly specialised: only effective against certain bacteria.
Other antibiotics are broad-spectrum antibiotics: attack a wide range of bacteria, including the ones that are beneficial to us.

There are a few ways in which antibiotics target bacteria:

  1. Inhibit the synthesis of bacterial cell wall — when the cell wall is weakened, it is unable to resist expansion when water enters the cell by osmosis, hence bacterium bursts and die.
  2. Inhibit cell membrane functions — by breaking up the membrane, causing the bacteria to no longer be protected from its environment.
  3. Inhibit protein synthesis in ribosomes — inhibiting growth.
  4. Inhibit enzyme action in cytoplasm — for example, inhibiting action of enzyme required for bacterium to synthesise folic acid will inhibit growth.
19
Q

Why Antibiotics are Not Effective on Viruses

A

Antibiotics are not effective on viruses due to structural differences between viruses and bacteria.

Cellular structures that antibiotics target in bacteria are absent in viruses.

  • They act on bacterial cell walls. Viruses do not have cell walls.
  • They break up cell membranes. Viruses do not have cell membrane.
  • They act on ribosomes, inhibiting protein synthesis and growth. Viruses do not have ribosomes and they do not grow.
20
Q

How Antibiotic Resistance Occurs

A

Ways Bacteria develop antibiotic resistance:

  1. Antibiotic resistance occurs when bacteria develop resistance to specific antibiotics after being exposed to it. Due to variation within the bacteria population, there are bacteria which may be less sensitive to antibiotics, and they manage to evade the action of the antibiotics, espeically when the prescribed course of antibiotics is not completed. When they survive, they go on to reproduce and more bacteria in the population are now less sensitive to the antibiotics. Over time, the bacteria will acquire resistance to the antibiotics.
  2. Bacteria can also develop antibiotic resistance through contact with other resistant bacteria which pass their genes to them, forming a new antibiotic-resistant ‘strain’ of the bacteria.
21
Q

Causes of the Increased Occurance of Antibiotic Resistance

A

Causes of the increased occurance of antibiotic resistance:

  1. Overuse of antibiotics on minor infections.
  2. Misuse of antibiotics when they are prescribed for viral infections.
  3. Not completing the course of antibiotics prescribed by doctors.
22
Q

‘Superbugs’

Definition

A

‘Superbugs’ are bacteria that are resistant to many types of antibiotics.

23
Q

How to Prevent the Emergence of Antibiotic Resistance Bacteria

A
  1. Using antibiotics only when necessary and not on minor infections.
  2. Not misusing antibiotics to treat a viral infection.
  3. Completing the course of the antibiotics prescribed by doctors.
24
Q

Vaccine

What it is

A

A vaccine contains an agent that resembles a pathogen and prevents infectious diseases by stimulating white blood cells to quickly produce antibodies when the pathogen invades.

25
Q

How Vaccines Work

A
  1. Antigens are substances that can trigger the production of antibodies by white blood cells, such as proteins on the surfaces of pathogens.
  2. When a vaccine, which contains an agent that resembles a pathogen (has the same antigens), enters the body, it stimulates white blood cells to produce antibodies to destroy the pathogen.
26
Q

Antibodies

What they are + Characteristics

A

Antibodies are proteins that are produced by lymphocytes to destroy a pathogen.

  • They are specific in action. Antibodies that destoy one type of pathogen will be ineffective against another type of pathogen.
  • Antibodies can also tag pathogen for destruction by white blood cells.
27
Q

Primary & Secondary Immune Response

Explain

A
  • When the vaccine is given, white blood cells become activated and produce antibodies, just as they do when they encounter an actual disease-causing organism. This is called the primary immune response.
  • The next time the person is exposed, there is a sharp increase in the level of antibodies produced. This is called the secondary immune response.
28
Q

Explain Why Booster Shots are Required

A

As time passes, the level of antibodies will begin to fall.
It will remain high only if the person is repeatedly exposed to the same antigen, either by accident or as the result of a booster shot.
If natural exposure does not occur, the amount of antibodies fall slowly, sometimes reaching a low, unprotective level.

Y4 Biology (10 decks)

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