4.3.1.1 Communicable (infectious) diseases

Question 1

Pathogens:

Answer 1

• micro-organisms which cause infectious diseases
• inc. viruses, bacteria, protists or fungi

Question 2

How can pathogens infect plants or animals?

Answer 2

• can infect plants or animals spread through direct contact, water or air

Question 3

How are communicable diseases transmitted?

Answer 3

• by air - pathogens can be carried in the air and then breathed in (a common example is a droplet infection, which is when sneezing, coughing or talking expels pathogens in droplets which can be breathed in)
• direct contact - e.g. handshakes, kissing/sexual activity
• indirect contact - touching contaminated surfaces
• through contaminated water - e.g. through drinking or coming into contact with dirty water
• spread by use of a vector - e.g. mosquitoes
• spread through contaminated food by eating it

Question 4

How do pathogens make people feel ill?

Answer 4

• produce toxins or damage cells making people feel ill
• reproduce very quickly inside body

Question 5

Why are diseases much more spread than 100yrs ago?

Answer 5

• 100yrs ago diseases like SARS and Ebola wouldn’t have left their country of origin
• due to ease of air travel
• people can fly around world and spread diseases to places they would’ve never otherwise reached
• many Native Americans killed by diseases when the Colonial “Settlers” arrived, bringing strains of bacteria and virus their bodies had no immunity

Question 6

How can the damage that communicable diseases cause to populations be reduced?

Answer 6

• can be reduced by limiting the spread of pathogens
• improve hygiene: hand washing, using disinfectants, isolating raw waste, using tissues and handkerchiefs when sneezing
• isolating/reducing contact with infected individuals
• removing vectors: using pesticides and removing their habitat
• vaccination: by injecting a small amount of harmless pathogen into an individuals body, they can become immune to it so it won’t infect them - means they can’t pass it on

Question 7

Are viruses cells?

Answer 7

No

Question 8

What is the size of viruses?

Answer 8

• very small
• 20 - 400nm

Question 9

How do viruses make individuals feel ill?

Answer 9

• viruses replicate themselves by invading cells
• viruses live and reproduce rapidly inside cells, causing cell damage
• the cell bursts and release new viruses into the bloodstream
• the damage and destruction of the cells makes you feel ill

Question 10

Site of reproduction for viruses:

Answer 10

inside cells

Question 11

Diagram of virus:

Answer 11

Question 12

How small are bacteria?

Answer 12

• small
• 0.2 - 2.0μm

Question 13

How do bacteria make individuals feel ill?

Answer 13

• reproduce rapidly
• may produce toxins that damage tissues that makes you feel ill

Question 14

How do bacteria cells multiply quickly?

Answer 14

• multiply very quickly by dividing process called binary fission

Question 15

What is the structure of bacteria?

Answer 15

• Essentials structure: cell wall, cell membrane, cytoplasm, nuclear material
• Particular structures: capsule, flagella, pili, spore

Question 16

Site of reproduction for bacteria:

Answer 16

human body

Question 17

Diagram of bacteria:

Answer 17

Question 18

What is the size of fungus?

Answer 18

3-4μm

Question 19

How are fungus different to plant cells?

Answer 19

similar to plant cells but with a chitin cell wall

Question 20

Where do fungus reproduce well?

Answer 20

• reproduce well in damp conditions

Question 21

What can fungus cause?

Answer 21

• cause severe itching and damage to skin - can lead to secondary infections
• produce spores which can be spread to other organisms

Question 22

What is the structure of fungi?

Answer 22

• can either be unicellular or have a body made of hyphae (thread-like structures)
• fungi grow in network of fibres called hyphae
• cytoplasm near cell membrane
• multinucleate
• cell wall made of chitin

Question 23

Site of reproduction for fungi:

Answer 23

On skin

Question 24

Diagram of fungi:

Answer 24

Question 25

What is the size of protists?

Answer 25

10 - 100μm

Question 26

What are protists?

Answer 26

• single-celled parasites
• some are parasitic - use humans and animals as their hosts (to live on and inside, causing damage)

Question 27

What do protists use humans or animals for?

Answer 27

often use humans or others animals as hosts to complete their life cycle, and use vectors e.g. mosquitoes to reach them

Question 28

What do protist diseases often stop humans from doing?

Answer 28

often stop humans from moving much, to allow vectors to feed easier

Question 29

What effect on the body do protists have?

Answer 29

cause fevers

Question 30

Site of reproduction for protists:

Answer 30

In blood

Question 31

Diagram of protist:

Answer 31

Question 32

What do bacteria and viruses both do?

Answer 32

bacteria and viruses both reproduce rapidly inside the body

Question 33

What is the difference between bacteria and viruses?

Answer 33

• bacteria damage outside of cells - don’t need to get into cells to cause damage
• viruses do damage inside cell - must get into host cells to cause damage

Question 34

What is the structure of viruses like?

Answer 34

• hexagonal in shape
• has a protein coat made up of many small subunits
• contains a strand of genetic material (DNA or RNA) inside protein coat

Question 35

How do fungi digest food?

Answer 35

produce enzymes to digest food

Question 36

How do fungi reproduce?

Answer 36

reproduce by producing spores

Question 37

What is the structure of protists?

Answer 37

• single-celled eukaryotic organisms
• DNA enclosed in a nucleus
• have cell membrane and organelles
• often have quite complex life cycle and use vectors to help transmit the disease