Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

A LEVEL BIOLOGY > 4 - Microbiology (C1) > Flashcards

4 - Microbiology (C1) Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

What does aseptic technique prevent?

A
  • Contamination of the environment by the microbes being handled
  • Contamination of microbial cultures by unwanted microbes from the environment
  • Contamination of the experimentor
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the function of the plasma membrane of prokaryotes?

A
  • Barrier between environment and cytoplasm

- Controls entry and exit of substances in and out of cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the function of the peptidoglycan (murein) cell wall of prokaryotes?

A

Prevents lysis in a hypotonic solution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the function of the capsule of prokaryotes?

A
  • Outer later of mucopolysaccharide slime which can glue bacteria together and stick them to surfaces
  • Protects the bacteria from attack by other cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the function of the pili of prokaryotes?

A

Attaches to surfaces and transfers plasmids by conjugation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the function of the plasmid of prokaryotes?

A
  • Circular DNA which contains extra bacterial genes for antibiotic resistance
  • Can be exchanged between bacteria during conjugation allowing the spread of antibiotic resistance
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What shape is bacillus?

A

Rod shaped

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What shape is coccus?

A

Sphere

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What shape is spirillum?

A

Spiral

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are the metabolic requirements for microbes?

A
  • Suitable temp
  • Suitable pH
  • O2 requirements - controls growth of pathogenic bacteria which grow at a faster rate in anaerobic conditions
  • Carbon source - provides energy
  • Nitrogen source - required for synthesis of proteins, amino acids, DNA and RNA
  • Growth factors e.g. vits and mins - essential for growth
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are some important parts of aseptic technique?

A
  • Autoclave all glassware at 121 degrees for 15 mins
  • Open petri dish at a small angle
  • Keep a roaring blue flame on the bench
  • Keep McCartney caps in hand and flame neck of bottle
  • Flame loops, wires (until red hot) and glass spreaders (using ethanol) to red heat in a Bunsen flame
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Why during aseptic technique must all glassware be autoclaved at 121 degrees for 15 mins?

A

To kill bacteria and spores

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Why during aseptic technique must petri dish lids be opened at small angles?

A

To prevent bacteria entering petri dish

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Why during aseptic technique must a blue flame be kept roaring on the bench?

A

To create a convection current to uplift air away from cultures

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Why during aseptic technique must McCartney caps be kept in hand?

A

To not contaminate the desk

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Why during aseptic technique must the neck of McCartney bottles be flamed?

A

To create a convection current to lift air from broth

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Why during aseptic technique must loops, wires and glass spreaders be flamed?

A

To kill bacteria

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

How is a viable count of cells done?

A

Serial dilution is used and colonies are grown on agar plates and counted

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

How is a total count of cells done?

A

Serial dilution is used, and a haemocytometer is used to count the cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is the difference between a viable count and total count of cells?

A

Viable - only living cells are counted

Total - both living and dead cells are counted

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What are advantages and disadvantages of viable counts of cells?

A

+ Counts living cells

  • Long process
  • If culture is mixed some cells may take longer to grow than others
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What are advantages and disadvantages of total cell counts?

A

+ Quick
+ Can be used to count several types of cells
- Difficult to count if they clump

23
Q

Why are bacteria cultures diluted before being counted?

A

As otherwise there will be too many to count

24
Q

Why would it be inaccurate to choose a plate of bacteria to count with less than 50 colonies?

A

Unrepresentative, unreliable result

25
Q

Why would it be inaccurate to choose a plate of bacteria to count with more than 100 colonies?

A

Clumping would occur so individual colonies wouldn’t be able to be identified

26
Q

Why does the stationary phase occur in bacterial growth?

A
  • Population has reached its maximum size
  • Division rate = death rate
  • Lack of nutrients or too many toxins
  • Unlike wild populations, they DON’T have a carrying capacity and aren’t controlled by density dependent factors
27
Q

Why during aseptic technique should cultures be incubated at 28 degrees not 37 degrees?

A

As this would provide optimum conditions for the growth of a pathogen

28
Q

Why during aseptic technique should the lids of petri dishes be secured with 2 strips of tape but not completely sealed?

A

To provide the microorganisms with some O2 to grow, otherwise it would provide anaerobic growth conditions for pathogens

29
Q

Why during aseptic technique should the bench be cleaned with Virkon before and after the experiment?

A
  • Before: to prevent bacteria on the bench contaminating the microbes being handled
  • After: to kill microbes used in the experiment that have contaminated the bench
30
Q

What is the process of serial dilution plating?

A
  • Add 9cm3 sterile water to 6 sterile tubes
  • Swirl the culture tube to mix the contents and using a sterile syringe add 1cm3 from this tube to the next
  • Continue until all 6 tubes have been done
31
Q

What is the process of serial dilution?

A
  • Using a sterile syringe transfer 0.5cm3 of each sample onto a sterile agar plate
  • Use a glass spreader and aseptic techniques to spread over the plate
  • Repeat this twice to give 3 plates for each dilution
  • Secure the lids of the plates with 4 strips of tape and label name of bacteria, date, dilution
  • Incubate plates at 28degrees for 24-48 hours
  • Once colonies have grown, choose a plate with 50-100 colonies
  • Count the colonies in the 3 plates for this dilution and calculate mean
  • Calculate number of microbes in original
32
Q

How can you calculate the number of bacteria in the original sample from a diluted sample?

A
  • Number of colonies x dilution factors e.g. if 1 in 1000, times by 1000
  • Correct for different sample sizes, e.g. check if asked for 1cm3 or 0.5cm3
33
Q

What is the process of gram staining?

A
  • Smear bacteria onto slide and ‘heat fix’
  • Apply crystal violet (purple dye)
  • Apply iodine (mordant)
  • Wash with alcohol (decolorisor)
  • Apply safranin (counterstain)
34
Q

Why in gram staining is the bacteria smeared onto a slide and heat fixed?

A

To prevent it being washed off by staining

35
Q

Why in gram staining is crystal violet applied?

A

It binds to the peptidoglycan cell wall and so stain all cells purple

36
Q

Why in gram staining is iodine applied?

A

To ensure the crystal violet fixes firmly to the cell wall

37
Q

Why in gram staining is the bacteria washed with alcohol?

A

To remove unbound crystal violet and lipopolysaccharide:

  • Gram neg- lose their stain and become colourless
  • Gram pos+ remain purple
38
Q

Why in gram staining is safranin applied?

A
  • Stains gram neg- cell wall red/pink

- Gram pos+ remain purple

39
Q

After being gram stained what colour are gram positive+ bacteria?

A

Purple

40
Q

After being gram stained what colour are gram negative- bacteria?

A

Red

41
Q

What is the study of small organisms, including bacteria, important for?

A
  • Medicine / healthcare
  • Food industry e.g. dairy
  • Water quality
42
Q

What bacterial grouping is diplo?

A

A pair

43
Q

What bacterial grouping is staphylo?

A

A clump / ‘stack’

44
Q

What bacterial grouping is strepto?

A

A chain / ‘strap’

45
Q

What is the cell wall chemistry of gram positive bacteria?

A
  • Thick peptidoglycan cell wall (penicillin disrupts cross links + causes cell to burst by osmosis = lysis)
  • Stain with crystal violet and turn purple
46
Q

What is the cell wall chemistry of gram negative bacteria?

A
  • Thin peptidoglycan cell wall
  • Protective outer layer of lipopolysaccharide
  • More difficult for antibiotics, enzymes and antibodies to control them
  • Stain purple but when washed with ethanol, purple outer coat is dissolved, producing clear cells
  • When a 2nd (counter stain) of safranin is added, the newly exposed peptidoglycan stains red
47
Q

What are the names of bacteria that can survive at extremely high temperatures?

A

Thermophiles

48
Q

What does penicillin do to gram positive bacteria?

A
  • Prevents the bonds inter-linking peptidoglycan molecules from forming
  • This is significant when the bacteria make new cell walls when they divide
  • It makes the cell walls weak, and water uptake by osmosis bursts the cell
  • Gram neg- bacteria are unaffected as they have a protective outer lipopolysachharide layer in their cell walls
49
Q

Why are human cells not harmed by penicillin?

A

As animal cells don’t have cell walls

50
Q

As gram negative bacteria are resistant to penicillin, how can their number be controlled?

A

With antibiotics that interfere with the cell’s ability to make proteins

51
Q

What does a ‘defined’ medium contain?

A

Only known ingredients

52
Q

What does an ‘undefined’ medium contain?

A

Components that are not all known

53
Q

What does a selective medium contain?

A

Only components that allow certain bacteria to grow

A LEVEL BIOLOGY (13 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions