Chapter 11: Infectious diseases

Question 1

What is a disease

Answer 1

A disease is a condition that causes the body to function less effectively

Question 2

How infectious diseases spread?

Answer 2

• through droplets in the air
• by direct contact
• by contaminated food and water

Question 3

How diseases spread via droplets?

Answer 3

• when someone coughs or sneezes, numerous tiny droplets are expelled
• these droplets contain pathogens
• when people breathe these droplets, they become infected
• therefore it is advised to wear masks when you are sick

Question 4

How diseases spread by direct contact?

Answer 4

• by exchanging of bodily fluids ( via sexual intercourse or from other to child when breastfeeding
• when blood from infected person comes into contact with mucous membranes (e.g. membranes lining the eye, nose and mouth of infected person
• when blood from infected person comes into contact with bloodstream of uninfected person through cuts/injections

Question 5

How diseases spread by food and water

Answer 5

• food and water can be contaminated with pathogens
• happens when food and water are not properly handled/stored
• prevented by practising hygienic food preparation and storage; having good personal hygiene; maintaining a clean water supply; ensuring proper sewage treatment

Question 6

Structure of bacterial

Answer 6

1. singular circular DNA as genetic material
2. cell wall
3. cell membrane
4. ribosome
5. flagella (one or more)
6. plasmids (circular DNA molecule)
7. cytoplasm

Question 7

Structure of virus

Answer 7

1. Protein coat (encloses genetic material that is either DNA or RNA)
2. Genetic material
   - does not contain cellular structures
   - does not perform living functions (eg. growth and respiration), except reproduction
   - reproduction occurs as host cell contains necessary materials for reproduction

Question 8

Influenza

Answer 8

• a disease that attacks respiratory system
• caused by influenza virus
• transmitted through droplets or direct contact with contaminated objects before touching eyes, nose or mouth
• produces signs and symptoms such as high fever, headaches, stuffy nose, cough, sore throat and muscle aches

Question 9

Methods to prevent spread of influenza

Answer 9

1. get the influenza vaccination
2. avoid close contacted to infected people
3. if you are sick, keep your distance from others
4. cover your mouth and nose with a tissue when you sneeze or cough to prevent droplets from spreading
5. wear a surgical mask
6. wash your hands with soap & water / rub with disinfectant
7. avoid touching eyes, mouth and nose
8. take antiviral drugs prescribed by doctors

Question 10

Pneumococcal disease

Answer 10

• cause by pneumococcus bacteria
• bacteria may attack diff parts of body
• transmitted through respiratory droplets
• signs and symptoms include fever, headache, vomiting, cough, chest pain, and rapid breathing

Question 11

Methods to reduce pneumococcal disease

Answer 11

1. get the pneumococcal vaccine
2. avoid coming into close contact with infected people
3. if you are sick, keep your distance from others
4. cover your mouth and nose when you cough
5. wear a surgical mask when you are sick
6. wash your hands with soap and water/ rub with disinfectant
7. avoid touching mouth, eyes and nose
8. take antibiotics prescribed by doctors

Question 12

What are vaccines

Answer 12

• contains an agent that resembles pathogen
• prevents infectious diseases by stimulating white blood cells to quickly produce antibodies when pathogens invade

Question 13

How vaccines work

Answer 13

1. When agents enters bloodstream, white blood cell attaches to agent
2. wbc are stimulated to produce antibodies
3. antibodies destroy the agent in vaccines
4. some of these white blood cells remain in bloodstream
5. in the future, if live pathogen enter bloodstream, wbc will recognise them and quickly produce antibodies to destroy pathogens before they infect our cells

Question 14

What are antibodies

Answer 14

• proteins that are produced to destroy a pathogen
• specific in action
• only can destroy one type of pathogen and not others
• antigens trigger the production of antibodies

Question 15

What are antibiotics

Answer 15

• drugs used to treat bacterial infections
• made by microorganisms
• used to kill / inhibit growth of bacteria
• ineffective against viruses

Question 16

How antibiotics work

Answer 16

1. Inhibit synthesis of cell wall. When cell walls are weakened, water enters cell via osmosis. Cell expands, bursts and dies.
2. Inhibits cell membrane function by breaking up bacterial cell membrane. W/o cell membrane, cell is no longer protected from its environment as any substances can move into bacterial cell
3. Inhibits protein synthesis in ribosomes by binding to them, preventing ribosomes from taking part in protein synthesis, inhibiting growth
4. Inhibits enzyme action in cytoplasm which synthesises folic acid, which is required for the bacteria cell’s growth. This inhibits its growth

Question 17

Why antibiotics can kill bacteria by not viruses

Answer 17

• they act on cell walls, viruses don’t have them
• they break up cell membranes, viruses don’t have them
• they act on ribosomes, inhibiting protein synthesis and growth. Viruses do not have ribosomes and they do not grow

Question 18

How antibiotics resistance happens

Answer 18

1. In a population of bacterial cells, some are more sensitive to antibiotics X, while some are less sensitive
2. When X is taken, the more sensitive cells die, while the less sensitive cells are nit easily killed and may survive
3. if prescribed course of X is completed, chances of all bacterial killed is higher
4. if course is not completed, less sensitive cells will multiply and increase in number
5. this causes population of bacteria cells to be resistant to X
6. other antibiotics are required to kill the bacteria population

Question 19

Ways to reduce antibiotic resistance

Answer 19

1. not misusing or overusing antibiotics
2. completing full course of antibiotics prescribed by doctor
3. use antibiotics only when necessary