M4 : ch 12 - communicable diseases

Question 1

what is a disease

Answer 1

something that impacts social, physical + mental health

Question 2

communicable diseases

Answer 2

• transmitted by another organism that infects another –> these infective organisms are known as pathogens –> bacteria, fungi, viruses, protists (parasites)
• often infectious –> can be passed from organism to organism

Question 3

what are the type of pathogens

Answer 3

• bacteria
• fungi
• viruses
• protists (parasites)

Question 4

Bacteria

Answer 4

• most common organism for infection
• not all bacteria are pathogens
• prokaryotes –> don’t have membrane-bound organelles
• classified into 2 categories:
  Basic shape:
• rod, comma, spherical, spiralled, corkscrew
  Cell wall:
• gram positive - appear blue-purple after gram staining (e.g. MRSA)
• gram negative - appear red after gram staining (e.g. E.coil)
• the type of membrane affects how bacteria respond to antibiotics

Question 5

Viruses

Answer 5

• non living infectious agents
• a nucleic acid surrounded by a protein –> capsid-protein coat
• infect cells by inserting/injecting its own RNA into the DNA of a cell –> infected cells then produce more viruses
• all natural viruses are pathogens
• affect all type of organisms - even bacteria –> bacteriophages
• lystic cycle
• lysogenic cycle

Question 6

protista/protists

Answer 6

• eukaryotic cells
• exist as single celled + multicellular organisms
• a small % act as pathogens
• can affect animals + plants (e.g. malaria - a plasmodium pathogen)
• often protists require a vector to transfer the disease (e.g. malaria - mosquito)

Question 7

fungi

Answer 7

• not major problems in animals, affect plants hugely
• eukaryotes, can be unicellular or multicellular
• many are saprophytes –> feed on decaying matter
• when fungi affects plants, they often infect the leaves - preventing photosynthesis
• fungi produce millions of spores that rapidly infect other organisms
• can cause ringworm, athletes foot, thrush

Question 8

viruses damaging tissues

Answer 8

• take over cellular metabolism
• viral genetic material inserted into genetic material host cell
• host cell makes more viruses which burst/lyse out of the cell –> destroying it

Question 9

protista/protists damaging tissues

Answer 9

takes over a cell, digests the insides + uses this as a medium to reproduce, before bursting out (lyse)

Question 10

fungi damaging tissues

Answer 10

digest + destroy living cells

Question 11

pathogens producing toxins

Answer 11

• most pathogenic bacteria produce a toxin –> which is poison
• this toxin damages the cells of the host organism –> often by breaking down the plasma membrane or inactivating enzymes
• some fungi also produce toxins

Question 12

animal pathogens/diseases

Answer 12

• Tuberculosis –> mycobacterium tuberculosis
• HIV/AIDS –> virus
• Malaria –> plasmodia - protozoan parasites (vectors) (protists)
• Athlete’s foot –> fungus - finia pedia

Question 13

Tuberculosis

Answer 13

• caused by bacteria: mycobacterium tuberculosis
• affects the respiratory system –> especially lungs
• airborne disease –> via droplets in air when person with TB speaks, coughs + sneezes etc
• can enter + lie dormant (for years)
• if a patient’s immune system is unable to contain infection - active TB occurs:
  –> bacteria can multiply rapidly, destroying lung tissue, can be fatal
  –> coughing, shortness of breath, weight loss, fever, night sweats, loss of appetite, extreme fatigue
• treatment = antibiotics

Question 14

HIV/AIDS

Answer 14

• retro virus - infects T helper cells (lymphocytes)
  –> overtime immune system loses ability to fight infections as more T helper cells are destroyed
  –> disease develops into AIDS - result of complete immune system failure
• transmitted by certain bodily fluids –> semon, blood, breast milk etc
• sexual transmission, direct injection into blood stream, vertical transmission (infected mother to baby during pregnancy), breast feeding

Question 15

Malaria

Answer 15

• caused by protozoan parasites called plasmodia –> have a life cycle including 2 hosts:
• humans, the secondary host, become infected when bitten by mosquitos –> vector for disease
• infection has 2 phases:
  –> first = sexual reproduction in liver cells
  –> second = cycles of asexual reproduction within red blood cells

Question 16

Athletes foot

Answer 16

• fungal disease –> caused by finla pedia
• form of human ringworm that grows on + digests the warm moist skin between the toes
• causes cracking + scaling –> itchy + sore
• antifungal cream = effective cure

Question 17

What are the two ways pathogens can cause disease

Answer 17

Damaging cells:
- malaria parasites cause disease symptoms by bursting RBC

Producing toxins:
- exotoxins = secreted by living normal pathogen
- endotoxins = released when pathogen damaged

• symptoms of cholera caused by an exotoxin secreted by the bacteria vibrio cholerae –> it increases the secretion of chloride ions into the lumen of intestines –> can lead to severe diarrhoea

Question 18

How can diseases be transmitted

Answer 18

• direct –> athletes foot, HIV/AIDS
• airborne –> covid, flu
• waterborne –> cholera
• food –> salmonella
• vector –> maleria
• animals –> rabies

Question 19

factors affecting the spread of disease

Answer 19

• human demographics + behaviour –> sexually transmitted disease (HIV/AIDS), dengue fever
• economic development + land use –> malaria, plague. rabies, yellow fever, lyme disease
• microbial adaptation + change –> HIV/AIDS, malaria, influenza
• breakdown of public health measures (war, government changes, natural disasters) –> tuberculosis, cholera, rabies, diphtheria
• climate change (increase in temperature and humidity, flooding etc) –> malaria, cholera, dengue fever, yellow fever
• international travel –> malaria, cholera, covid