Communicable Diseases

Question 1

What are
pathogens

Answer 1

Microorganisms that cause illness and
diseases

Question 2

Pathogen
examples

Answer 2

Viruses, bacteria, protists and fungi

Question 3

How bacteria make
us ill

Answer 3

They release toxins into our body

Question 4

How viruses make
us ill

Answer 4

They enter our body cells, multiply inside
and then destroy/damage the body cells

Question 5

How we defend
ourselves against
pathogens

Answer 5

Produce antitoxins to neutralise the toxins
Produce antibodies which attach to the
antigens on the surface of pathogens and
slow them down
White blood cells engulf and ingest
pathogens

Question 6

What important
discovery did
Semmelweis
make?

Answer 6

Handwashing prevents the spread of
diseases. He insisted that doctors
washed their hands before examining
patients. This practice drastically reduced
deaths in hospitals.

Question 7

How do you treat a
bacterial infection?

Answer 7

With antibiotics.

Question 8

How do you treat
viral infections?

Answer 8

With antivirals which work on viruses
inside cells. This could damage the cells.
Other medicines can alleviate the
symptoms (e.g. painkillers).

Question 9

Why should we
avoid the overuse
of antibiotics?

Answer 9

To prevent the development of
superbugs. Due to mutations, some
pathogens are resistant to the antibiotic.
These pathogens survive and multiply. An
example of an antibiotic resistant
pathogen is MRSA.

Question 10

MMR vaccinates
against…

Answer 10

Mumps, measles and rubella

Question 11

How to grow
bacterial cultures in
the lab

Answer 11

Sterilise the agar plate
Sterilise the petri dish
Sterilise the inoculation loop by holding it
into a roaring Bunsen Burner flame.
Transfer bacteria onto agar plate using
sterile loop.
Place a lid on the petri dish to prevent
microorganisms from the air from entering.
Secure the lid loosely with Sellotape.
Make sure it is not sealed completely.
Without oxygen entering, very harmful
microorganisms would develop inside the
petri dish.

Question 12

At what
temperature is the
petri dish
incubated?

Answer 12

37oC in industry
25oC in schools to prevent harmful
bacteria from growing.

Question 13

How does a
vaccination work?

Answer 13

A weak/dead pathogen is injected. The body
produces antibodies.
When the live pathogen enters the body, the
body remembers to the specific antibodies
needed and produces it more quickly.

Question 14

What is a
communicable
disease?

Answer 14

An infectious disease.

Question 15

How do pathogens
spread?

Answer 15

Air, water, touch, contaminated food,
animal to animal.

Question 16

What is a vector?

Answer 16

An animal that spreads a communicable disease.

Question 17

Give examples of
viral diseases

Answer 17

Measles – fever, red skin rash. Can be
fatal. Passed on through air when people
sneeze or cough.
HIV – causes flu-like illness. Spread by
sexual contact or exchange of body fluids
and blood.

Question 18

Give examples of
bacterial diseases

Answer 18

Salmonella food poisoning – ingested in
food. Fever, cramps, vomiting, diarrhoea.
Gonorrhoea – STD; thick yellow or green
discharge from vagina or penis and pain
when urinating. Prevented by use of
condom.

Question 19

Give an example of
a fungal disease

Answer 19

Athletes foot – causes itching, flaking and
blistering.

Question 20

Give an example of
a protist disease

Answer 20

Malaria – causes recurrent periods of
fever and can be fatal. Controlled by
preventing the vector, the mosquito, from
breeding and by using mosquito nets to
prevent being bitten.

Question 21

What is the
human’s first line of
defence against
pathogens?

Answer 21

1. Skin – forms outer barrier and
   produces antimicrobial compounds
   which kill some pathogens.
2. Lysozymes in tears and saliva – an
   antibacterial enzyme which breaks
   down the cell walls of bacteria. Tears
   also contain antibodies.
3. Hairs and cilia – these are found in
   your nose, trachea, lungs, intestines.
   Together with mucus they act as a
   filter. The pathogens get stuck in the
   mucus and wafted out of the body by
   the cilia.
4. Stomach acid – pH low enough for
   many pathogens to not survive.

Question 22

What is the second
line of defence
against pathogens?

Answer 22

Phagocytes – white blood cells that engulf,
ingest and digest pathogens. Phagocyte
binds to pathogen, pathogen is absorbed
into the vacuole where enzymes break
down the pathogen. This is called
phagocytosis.

Question 23

What is the third
line of defence
against pathogens?

Answer 23

Lymphocytes – recognise antigens and
produce antibodies that are specific to
antigens. Antibodies help clump together
pathogens so they can be destroyed by
phagocytes.

Antitoxins – Lymphocytes produce antitoxins
to neutralise the action of the toxins released
by the pathogens.