Investigating Antibiotics And Antiseptics

Question 1

what is grown and cultured in growth mediums

Answer 1

bacteria and some other microorganisms

Question 2

what does a growth medium contain

Answer 2

• carbohydrates
• minerals
• proteins
• and vitamins they need to grow

Question 3

what are the two things the growth medium could be

Answer 3

• a nutrient broth solution

- or solid agar jelly

Question 4

what do bacteria grown on agar plates form

Answer 4

• visible colonies on the surface of the jelly

- which could spread out to give an even covering

Question 5

how do you make an agar plate

Answer 5

• hot agar jelly is poured into petri dishes
• when jelly cools and sets, incoulating loops are used to transfer microorganisms to the agar jelly
• the microorganisms then multiply

Question 6

what is a petri dish

Answer 6

a shallow round plastic dish

Question 7

how could you alternatively place the microorganisms on the agar jelly

Answer 7

• use a sterile dropping pipette to drop the microorganisms on to the jelly
• and use a spreader to get an even covering of bacteria

Question 8

why are cultures of microorganisms kept at 25C in school

Answer 8

harmful pathogens are less likely to grow at this temperature

Question 9

how is temperature managed when growing bacteria outside of school

Answer 9

• you may culture microorganisms at a higher temperature

- to provide the optimum conditions for growth

Question 10

what do antibiotics simply do

Answer 10

they kill bacteria inside the body

Question 11

what do antiseptics simply do

Answer 11

they kill bacteria outside the body

Question 12

what can you use to investigate the effect of antiseptics and antibiotics

Answer 12

cultures of bacteria

Question 13

what is the process of investigating the effects of antibiotics (and antiseptics alike)

Answer 13

• soak paper disks soaked in different types of antibiotics on an agar plate with an even covering of bacteria
• leave some space between the discs
• the antibiotic should diffuse into the agar jelly
• leave the plate for 48 hours at 25C

Question 14

what will antibiotic resistant bacteria do on the agar jelly compared to non-resistant bacteria

Answer 14

• the resistant bacteria will continue to grow on the agar around the paper discs
• while the non-resistant bacteria will die

Question 15

what is the inhibition zone

Answer 15

the clear area that is left where the bacteria have died

Question 16

what is the control in this experiment and why should you use it

Answer 16

• a paper disc that has not been soaked in an antibiotic
• you should use it because you can be sure that any difference between the growth of the bacteria around the control disc and the antibiotic disc is due to the effect of the antibiotic alone

Question 17

how will a more effective antibiotic against the bacteria be shown after the time is up

Answer 17

the antibiotic will have a larger zone of inhibition

Question 18

how do you avoid contamination by unwanted microorganisms which can affect your results

Answer 18

by using aseptic conditons

Question 19

what are the five things you can do to make sure the bacteria is in aseptic conditons

Answer 19

• sterilise petri dishes and growth medium
• sterilise the incoulating loop
• keep liquid cultures in a culture vial with a lid
• cover the petri dish with a lid
• store the petri dish upside down

Question 20

how do you sterilise the petri dishes and growth medium

Answer 20

• by placing them in a machine called an autoclave

- which uses steam at a high pressure and temperature to kill any microorganisms present

Question 21

how should the incoulating loop be sterilised

Answer 21

• by passing it through a flame

- so that any unwanted microorganisms are killed

Question 22

why should you keep liquid bacteria cultures in a cultural vial with a lid

Answer 22

• to prevent other microbes from getting in

- you should only be briefly removing the lid when transferring the bacteria

Question 23

why should the petri dish be stores upside down

Answer 23

to stop drops of condensation falling onto the agar jelly