4.6 Disease, Defence and Treatment

Question 1

What are the four main types of microorganisms?

Answer 1

bacteria, viruses, fungi, protists

Question 2

What are pathogens?

Answer 2

micro-organisms that cause infectious diseases

Question 3

How do bacteria cells make us ill?

Answer 3

they infect a host
reproduce themselves
spread from their host
then infect other organisms

Question 4

Describe the difference between the structure of bacteria and viruses

Answer 4

Bacteria- one celled organisms, consisting a cell wall, cell membrane, DNA, cytoplasm
Viruses- not cells, has some genes and a protein coat

Question 5

Why are viruses not considered to be alive?

Answer 5

because they can only reproduce inside the cell/host

Question 6

What happens to the skin if it is cut or grazed to prevent infection?

Answer 6

begins to heal itself, often by forming a scab, prevents infection as the skin acts as a physical barrier

Question 7

How does the nose prevent pathogens from entering the body?

Answer 7

it has internal hairs, which act as a physical barrier

Mucus in the nose traps pathogens before they can enter the lungs

Question 8

What are phagocytes?

Answer 8

white blood cells that ingest micro-organisms and digests them

Question 9

What are lymphocytes?

Answer 9

white blood cells that produce antibodies and antitoxins

Question 10

What are antibodies?

Answer 10

chemicals which recognise antigens on specific pathogens

Question 11

What are antitoxins?

Answer 11

A chemical produced by a lymphocyte which neutralises the toxins released by the pathogen

Question 12

What are antigens?

Answer 12

Patterns of molecules on the surface of pathogens which are recognised by antibodies

Question 13

Name two types of white blood cells

Answer 13

phagocytes

lymphocytes

Question 14

What is the role of a phagocyte?

Answer 14

1. They attract to pathogens in the blood and bind to them
2. Phagocyte membrane surrounds the pathogen and engulfs it
3. Enzyme found inside the phagocyte breaks down the pathogen and destroys it

Question 15

What is the role of a lymphocyte?

Answer 15

1. Lymphocytes should recognise the antigens on the pathogen
2. They detect the antigens as foreign and produce specifically shaped antibodies
3. Antibodies cause pathogens to stick together and make it easier for phagocytes to engulf them

Question 16

Which type of white blood cell is responsible for engulfing pathogens?

Answer 16

phagocytes

Question 17

Which type of white blood cell releases antitoxins?

Answer 17

lymphocytes

Question 18

Which type of white blood cell releases antibodies?

Answer 18

lymphocytes

Question 19

What is the name given to the protein markers on the outside of pathogens?

Answer 19

antigens

Question 20

What do lymphocytes produce in response to the antigens on pathogens?

Answer 20

antibodies

Question 21

What do lymphocytes produce in response to toxins released from pathogens?

Answer 21

antitoxins

Question 22

What do antibodies do?

Answer 22

help stick the pathogens together to enhance the activity of phagocytes

Question 23

Explain why antibodies are specific?

Answer 23

Antibodies have complementary shape to antigen which are specific for each type of pathogen

Question 24

Describe how the body responds when it is invaded by pathogens

Answer 24

1. Pathogens enter the blood
2. the pathogens have foreign antigens
3. the antigens are recognised as foreign by lymphocytes
4. they respond by releasing antibodies to the antigens
5. the antibodies attach to the pathogen
6. the attached antibodies help phagocytes destroy the pathogen

Question 25

State the name of a sudden change to a gene

Answer 25

mutation

Question 26

State ways by which pathogens are spread between people

Answer 26

coughing
sneezing
talking
sexual intercourse

Question 27

How do vaccines work?

Answer 27

Vaccines contain inactive pathogens
When person is injected, the white blood cells SLOWLY react to the inactive pathogens and produce antibodies
Memory cells are produced and remain in the bloodstream
If a person encounters a pathogen again, memory cells produce specific antibodies VERY QUICKLY if the same antigen is encountered the second time

Question 28

Why are people vaccinated?

Answer 28

The vaccine causes the immune system to produce complementary antibodies and create memory cells
A second exposure causes white blood cells to respond QUICKLY which prevents infection

Question 29

What are memory cells?

Answer 29

formed by lymphocytes once they have encountered a pathogen and made the antibodies

Question 30

What are antibiotics?

Answer 30

substances that slow down or stop the growth of bacteria

Question 31

What micro-organisms are not killed by antibiotics?

Answer 31

viruses

Question 32

Why are commonly prescribed antibiotics becoming less effective?

Answer 32

overuse of antibiotics
failing to complete the fully prescribed course by a doctor
use of antibiotics in farming

Question 33

What is the difference between a blind trial and double blind trial?

Answer 33

blind trial- only the patient are not told if they are in the trial group or placebo group
double blind trial- both the doctor and patient are not told if they are in the trial group or placebo group

Question 34

What is a placebo?

Answer 34

a pill that does not contain the active ingredient and so should have no effect on the patient