Infectious diseases in humans

Question 1

Disease

Answer 1

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

Question 2

Infectious diseases

Answer 2

Infectious diseases can be spread from person to person and is caused by pathogens (disease-causing organisms)

Example of pathogens:
- Bacteria
- Viruses

Question 3

Non-infectious diseases

Answer 3

Non-infectious diseases are not caused by pathogens

Example of non-infectious diseases:
- Asthma
- Diabetes

Question 4

Ways to spread infectious diseases

Answer 4

1. Through droplets in the air
   - Respiratory droplets expelled when a person coughs or sneezes may contain pathogens
2. Through direct contact
   - Exchange of bodily fluid can spread infectious diseases
3. Through contaminated food and water
   - Food and water can be contaminated with pathogens such as bacteria that cause cholera

Question 5

Bacteria

Answer 5

Bacteria:
- has a cell wall, cell membrane, cytoplasm and ribosomes
- has DNA
- has no nucleus

Question 6

Viruses

Answer 6

Viruses:
- Has a protein coat enclosing its genetic material
- Genetic material of either DNA or RNA
- Has no ribosomes

Question 7

Pneumococcal disease (bacteria)

Answer 7

Signs and symptoms:
- High fever
- Headache
- Vomiting
- Cough
- Chest pain
- Rapid breathing

Transmitted by;
- Respiratory droplets

Question 8

Influenza (Virus)

Answer 8

Signs and symptoms:
- High fever
- Headache
- Cough
- Stuffy nose
- Sore throat
- Muscle ache

Transmitted by:
- Respiratory droplets
- Touching contaminated objects before touching own eyes, mouth and nose

Question 9

Vaccines

Answer 9

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

Process that vaccine prevents diseases:

1. White blood cell binds to the agent
2. White blood cell is stimulated to divide
3. Antibodies are produced by white blood cells
4. Antibodies destroy pathogen
5. Some white blood cells remain in the bloodstream for a long time as memory cells. In the future, when the same pathogen enters the body, memory cells can recognise and produce the antibodies to destroy it

Question 10

Antibiotics

Answer 10

Antibiotics are drugs used to treat bacterial infections but are ineffective against viruses

Antibiotics act on bacteria by inhibiting:
1. Synthesis of cell wall
- causing cell wall to be weakened, and water to enter the cell via osmosis and causing the cell to expand and burst, killing it
2. Protein synthesis of ribosomes
- Preventing the ribosomes from taking part in protein synthesis and inhibiting its growth

Question 11

Antibodies ineffectivity against viruses

Answer 11

Antibodies act on:
1. bacterial cell wall while viruses do not have cell wall
2. Ribosomes when viruses do not have ribosomes

Question 12

Development of antibiotic resistant bacteria

Answer 12

1. In a population of bacterial cells, there are some bacterias more sensitive to a type of antibiotic and other bacteria not as sensitve
2. When the full course of the antibiotic is taken, there is a higher chance that all bacteria are killed
3. However when the course of the antibiotic is not completed, the less sensitive bacteria may survive and multiply in numbers

Question 13

Reducing antibiotic resistance

Answer 13

Can be done by:
- Not overusing or misusing antibiotics
- Completing the full course of antibiotics as prescribed by doctors
- Use antibiotics only when necessary