Defending Against Disease

Question 1

Why can’t antibiotics destroy viruses?

Answer 1

• viruses reproduce using your own body cells, makings it difficult to develop drugs to destroy just the virus without killing the body’s cells

Question 2

Why do bacteria become resistant to antibiotics?

Answer 2

• bacteria can mutate and these mutations cause them to be resistant to an antibiotic
• when you treat the infection, only non-resistant strains of bacteria will be killed
• the individual resistance bacteria will survive and reproduce, and the population of resistant strain will increase
• vaccinations may no longer work against this resistant strain
• new resistant strain may spread rapidly in a population of people because they are not immune and there is no effective treatment
• it is important to stop over-prescribing antibiotics and avoid s=using them inappropriately

Question 3

What are pathogens?

Answer 3

• microorganisms that enter the body and cause disease

- they cause infectious diseases

Question 4

How do you make sure paper disc experiments are reliable?

Answer 4

• use a control that hasn’t been soaked
• you can be sure that any difference between the growth of bacteria around control disc and around antibiotic disk is due to the effect of the antibiotic alone

Question 5

How do vaccines work?

Answer 5

• vaccines inject small amounts of dead or inactive microorganisms. these carry antigens, which cause your body to produce antibodies to attack them
• if live microorganisms appear, the white blood cells can rapidly mass produce antibodies to kill off the pathogen

Question 6

What are viruses?

Answer 6

• they are not cells ( they are tiny)
• they replicate themselves by invading your cells and using the cells’ machinery to produce many copies of themselves
• cells will usually burst, releasing all the new viruses
• cell damage is what makes you feel ill

Question 7

How do you grow bacteria in petri dish without contamination?

Answer 7

• sterilise petri dish and culture medium
• pass inoculating loop through a flame to sterilise it
• lid should be kept on before exacter are transferred
• only lift the lid a little to decrease unwanted microorganisms
• after transferring bacteria, lid of dish should be lightly tapped to stop microorganism from air getting in
• should be stored upside down to stop bacteria falling onto the agar surface

Question 8

What are bacteria?

Answer 8

• bacteria: very small cells which can reproduce rapidly inside your body
• they make you feel ill by: - damaging your cells, - producing toxins

Question 9

What do white blood cells do?

Answer 9

• phagocytes consume: white blood cells engulf foreign cells and digest them
• lymphocytes produce complementary antibodies: each invading cell has antigens on its surface. When white blood cells come across a foreign antigen, they will produce proteins called antibodies to lock onto and kill the invading cells. the antibodies are specific to that type of antigen. antibodies are produced rapidly and carried around the body to kill all similar bacteria or viruses. if the person is infected with the same pathogen again, the white blood cells will rapidly produce antibodies to kill them. they are immune to that pathogen
• lymphocytes produce antitoxins: these counteract toxins produced by the invading bacteria