Microbiology

Question 1

What is the function of the plasma membrane in prokaryotic cells?

Answer 1

Barrier between the environment and the cytoplasm

Question 2

What is the function of the cell wall in prokaryotic cells?

Answer 2

Prevents lysis in hypotonic solutions

Question 3

What is the cell wall made of in prokaryotic cells?

Answer 3

Peptidoglycogen

Question 4

What is the function of the circular DNA in prokaryotic cells?

Answer 4

Contains the genes

Question 5

What are the functions of the capsule in prokaryotic cells?

Answer 5

Outer layer of slime. Glues bacteria together. Sticks to surfaces and protects bacteria from attack

Question 6

What is the function of the ribosomes in prokaryotic cells?

Answer 6

Synthesis of proteins

Question 7

What is the function of the pili in prokaryotic cells?

Answer 7

Attach to surfaces

Question 8

What is the function of the flagellum in prokaryotic cells?

Answer 8

Used for mobility

Question 9

What is the function of the plasmids in prokaryotic cells?

Answer 9

Contain extra bacterial genes

Question 10

What are the rod shaped bacteria called?

Answer 10

Bacillus

Question 11

What shape are bacillus bacteria?

Answer 11

Rod shaped

Question 12

What are the spherical bacteria called?

Answer 12

Coccus

Question 13

What shape are coccus bacteria?

Answer 13

Spheres

Question 14

What are the spiral bacteria called?

Answer 14

Spirillum

Question 15

What shape are spirillum bacteria?

Answer 15

Spiral

Question 16

What are the metabolic requirements for microbes?

Answer 16

Suitable temperature
Suitable pH
Oxygen
Carbon source
Nitrogen source
Growth factors e.g. vitamins and minerals

Question 17

Why is a suitable temperature a metabolic requirement for microbes?

Answer 17

Allows enzyme activity

Question 18

Why is a suitable pH a metabolic requirement for microbes?

Answer 18

Allows enzyme activity

Question 19

Why is oxygen a metabolic requirement for microbes?

Answer 19

Aerobic respiration - acts as the final electron acceptor in the electron transport chain

Question 20

Why is a carbon source a metabolic requirement for microbes?

Answer 20

Aerobic respiration - it provides the essential building blocks for their cells and serves as a source of energy

Question 21

Why is a nitrogen source a metabolic requirement for microbes?

Answer 21

Protein synthesis

Question 22

What does the term obligate aerobes mean?

Answer 22

Oxygen required for the bacteria to grow and divide

Question 23

What does the term obligate anaerobes mean?

Answer 23

Absence of 02 is required for bacteria to grow and divide

Question 24

What does the term facultative anaerobes mean?

Answer 24

Bacteria grow and divide in both conditions
However faster growth and division in aerobic conditions

Question 25

What is the purpose of using aseptic techniques?

Answer 25

Prevent contamination of: The environment by the microbes being handled Microbial cultures from unwanted microbes in the environment

Question 26

What are five different aseptic techniques?

Answer 26

Autoclaving all glassware to 121 degrees for 15 mins Open petri dish lids at a small angle Keep a roaring blue flame on the bench Keeping McCartney caps in hand and flaming the end of the bottle Flaming loops, wires and glass spreaders

Question 27

What is the reason for autoclaving all glassware to 121 degrees for 15 mins?

Answer 27

Kill bacteria and spores

Question 28

What is the reason for opening petri dish lids at a small angle?

Answer 28

Prevent bacteria entering the petri dish

Question 29

What is the reason for keeping a roaring blue flame on the bench?

Answer 29

Create a convection current to uplift air away from cultures

Question 30

What is the reason for keeping McCartney caps in hand and flaming the end of the bottle?

Answer 30

Prevents contamination of desk and creates a convection current to life air away from the broth

Question 31

What is the reason of flaming loops, wires and glass spreaders?

Answer 31

Kill bacteria

Question 32

What is the structure of gram positive bacteria?

Answer 32

Thick peptidoglycan layer followed by a plasma membrane

Question 33

What is the structure of gram negative bacteria?

Answer 33

Outer lipopolysaccharide membrane followed by a thin peptidoglycan layer followed by a plasma membrane

Question 34

What colour does gram positive bacteria go if stained?

Answer 34

Purple

Question 35

What colour does gram negative bacteria go if stained?

Answer 35

Pink

Question 36

Why does gram positive bacteria go purple if stained?

Answer 36

Dye not washed out by ethanol The thick peptidoglycan layer holds onto the crystal violet dye

Question 37

Why does gram negative bacteria go pink if stained?

Answer 37

Dye washed out by ethanol Thin layer does not hold onto the crystal violet dye

Question 38

What does a haemocytometer do?

Answer 38

Give total cell counts of bacteria

Question 39

What are the problems and solutions of counting bacteria?

Answer 39

Small - use a microscope Lots of them - dilute the sample Don't know if they are alive or dead - allow growth into colonies

Question 40

What is a viable count?

Answer 40

Only counting the living bacteria cells

Question 41

What is a total count?

Answer 41

Counting all the bacteria, alive and dead

Question 42

What are the advantages of a viable count?

Answer 42

Counts only living cells

Question 43

What are the disadvantages of a viable count?

Answer 43

Assumes one colony is from one bacteria - underestimate actual amount Takes a long time for count (24 hours) If mixed culture then some takes longer than others to grow

Question 44

What are the advantages of using a total count?

Answer 44

Quick - few minutes Used to count different cell types

Question 45

What are the disadvantages of using a total count?

Answer 45

Difficult to count clumps Both living and dead cells Difficult to count under a microscope

Question 46

What are the different stages in a cultures growth?

Answer 46

Lag phase Log (exponential phase) Stationary phase Death phase

Question 47

What happens in the lag phase in bacteria?

Answer 47

Synthesising new enzymes Reproductive rate is slow as little cell division

Question 48

What happens in the log (exponential) phase in bacteria?

Answer 48

Plenty of resources Max rate of cell division No limiting factors Reproductive rate > death rate

Question 49

What happens in the stationary phase in bacteria?

Answer 49

Limiting factors - toxins accumulate, nutrients running out Death = reproduction

Question 50

What happens in the death phase in bacteria?

Answer 50

Toxins build up to high levels Nutrients run out Death > reproduction

Question 51

Why should the term birth rate not be used when discussing a bacterial growth curve?

Answer 51

Produced by binary fission