MICR221 TEST QUESTIONS WITH ALL CORRECT ANSWERS
Define disinfectant - Answer-Chemicals that are capable of killing microorganisms, cannot be applied to tissues, in the laboratory they are applied to inanimate surfaces and used in discard jars and buckets
Define antiseptics - Answer-Chemical ag...
MICR221 TEST QUESTIONS WITH
ALL CORRECT ANSWERS
Define disinfectant - Answer-Chemicals that are capable of killing microorganisms,
cannot be applied to tissues, in the laboratory they are applied to inanimate surfaces
and used in discard jars and buckets
Define antiseptics - Answer-Chemical agents that kill or inhibit growth of
microorganisms and are sufficiently non-toxic to be applied to living tissues
Define preservatives - Answer-Included in pharmaceutical preparations or foods to
prevent microbial spoilage of the product
List the 12 ideal characteristics of chemical control agents - Answer-High antimicrobial
activity
Broad spectrum of antimicrobial activity
Stability (long periods for storage)
Homogeneity (chemical agent doesn't come out of solution)
Adequate solubility in solution
Minimum toxicity (to user and environment)
Detergent activity (solubilize and remove dirt and debris)
Minimum material effects (doesnt damage surfaces)
Minimum inactivation by organic material
Activity at normal temperatures
Deoderising ability
Cost
What are the four conditions influencing the effectiveness of antimicrobial agents? -
Answer-Population size
Properties of the chemical
Population composition
Environmental factors
Toxicity of the agent
Explain the effects of population size on the effectiveness of antimicrobial agents -
Answer-Only a fraction of the microorganisms die during a given time interval - 90% die
in the first minute, 90% of remaining die in the second minute therefore the death curve
is a logarithmic slope
It takes time to achieve sterility or to reduce microbial numbers to an acceptable level,
depends in part on the number of organisms present at the beginning of sterilisation
(important to minimise the initial bacterial load)
,Explain the effects of the properties of the chemical (dilution and pH) on the
effectiveness of antimicrobial agents - Answer-Narrow dilution range where they are
most effective
pH range = most effective 6-8, less effective 10+
Explain the effects of population composition on the effectiveness of antimicrobial
agents - Answer-Phase of growth: best target during the logarithmic/exponential phase
where MGT is shortest, microbes taking up chemicals from external environment so
killed most efficiently
Polymer or capsule production: could limit diffusion of chemical agent into cell
Altered cell wall or membrane
Modified sensitive sites
Cellular aggregation or biofilms
Resistant structures: endospores
Order the following microbes from least resistant to most resistant: bacterial
endospores, fungi, enveloped or medium sized viruses, mycobacteria, non-lipid or small
viruses, vegetative bacteria - Answer-enveloped or medium sized viruses
vegetative bacteria
fungi
non-lipid or small viruses
mycobacteria
bacterial endospores
Explain the effects of environmental factors on the effectiveness of antimicrobial agents
- Answer-Neutralisation by organic material (blood, body fluids)
Temperature = must be used at suitable temp where most active
Explain the effects of the toxicity of the agent on the effectiveness of antimicrobial
agents - Answer-Toxicity to the microbe maximised - target specifically
Toxicity to the user and environment minimised
Describe the type of complex polymers bacteria grow on and why they breakdown
polymers extracellularly - Answer-Polymers are large structures that bacteria are unable
to transport into the cell so they are broken down outside the cell by secreted enzymes
(amylases) to smaller transportable molecules and the monomeric units (glucose) are
transported into the cell for further attack by metabolic enzymes in the cytoplasm.
Costs the cell lots of energy
Give some polymer to monomer examples - Answer-P= starch, cellulose,
polysaccharide, proteins, organic matter, nucleic acids
M= amino acids, glucose, xylose, nucleotides
, Explain how bacteria grow on complex polymers - Answer-Bacteria are highly
specialised for polymer breakdown (eg.starch and cellulose) showing extreme metabolic
diversity
List some of the enzymes used by bacteria to grow on various polymeric substrates -
Answer-Proteases = proteins (peptides)
Cellulases = cellulose (glucose polymer b1,4)
Lipases = fats (glycerol and fatty acids)
Xylanases = xylan (xylose and other sugars)
Amylases = starch (glucose polymer a1,4)
Pectinases = pectin (galactose)
What is starch and what two molecules does it consist of? - Answer-Polysaccharide
produced by all green plants as an energy store, insoluble in water or alcohol.
-Linear and helical amylase (20-25%)
-Branched amylopectin (75-80%)
Describe the process of binary fission - Answer-1. Genetic material replicates itself
while the cell elongates
2. Genetic material migrates to either end of the cell and the septum begins to form
3. Septum then completely forms and the cell begins to separate
4. Two identical daughter cells are formed
How does population growth occur? - Answer-Occurs through binary fission, cell
number increases exponentially
Define the mean generation time - Answer-MGT = time it takes for one cell (and
therefore the whole population) to divide
How is the arrangement of a bacterial cell determined? - Answer-Determined by the
plane of division in binary fission
Division in one plane - Answer-Dipplococcus (chains = streptococcus)
Division in many planes - Answer-Cluster
Why are bacterial cells small? - Answer-A smaller cell has a larger surface area to
volume ration which is advantageous - especially for diffusion
List the 4 physical factors of growth requirement - Answer-Gaseous atmosphere
Temperature
pH
Osmotic pressure
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