exam 2 MC

Question 1

When 5% sheep red blood cells are added to a medium allowing the clinicians to discern which bacteria can destory the blood, the medium is considered a:

A. Selective
B. Enriched
C. Non-living
D. Differential
E. A and B
AB. C and B
AC. D and B

Answer 1

D and B (differential and enriched)

Question 2

Sterilization of bacteria may be accomplished by the following process except:

A. Pasteurization
B. Moist Heat
C. Filtration using a 0.22 micron filter
D. Radiation
E. ethylene oxide gas permeation

Answer 2

Pasteurization

does not sterilize, only sanitizes.

Question 3

A microorganism that grows optimally in our body is termed:

A. mesophile
B. thermophile
C. temperature tolerant
D. psychrophile
E. none of the above

Answer 3

Mesophile

grows in body temerature range (middle temps)

Question 4

Detergents with a 10 minute contact time kill microorganisms by:

A. Breaking down the peptidoglycan
B. solubilizing plasma membrane
C. Inhibiting protein synthesis
D. Blocking the replication of DNA
E. inhibiting exoenzymes

Answer 4

solubilizing the plasma membrane

80% of all disinfectants and antiseptics attack the plasma membrane

Question 5

What describes flash pasteurization?

Answer 5

Heating at 72 degrees celcius for 15 seconds

Question 6

The AUG functions for the amino acid methionine and as a _____.

Answer 6

Start Codon

Question 7

In general what is the name for a sanitizer that is toxic and should not be used on the skin of muscous membranes of the human body?

Answer 7

Disinfectant

Question 8

What is a term used to describe two microorganisms growing in an enviornment where one of the microorganisms benefits from the relationship and the other microorganism is neither harmed nor benefited from the relationship?

Answer 8

commensalism

a type of symbiotic relationship

Question 9

Describe how an amphipathic detergent/soap could be used as a chemical control agent but instead is usually only used as a mechanical control agent.

Answer 9

• Needs to have a contact time of 10 mins
• lipid loving side (hydrophobic) binds to dirt/debrea while the water loving side (hydrophilic) washed off with the water thus cleansing

Question 10

Why would chlorine be considered a more effective antimicrobial agent than ethyl alcohol?

Use the table to explain the contact time using alcohol necessary to control gram positive and gram negative bacteria.

Answer 10

• Chlorine requires a shorted contact time and smaller concentrations, and thus is more effective
• alcohol would be faster at getting rid of gram negative bacteria (E. coli) as it only has a contact time of 2 minutes. Gram psotive (S. aureous) requires 10 minutes to break down large peptidoglycan layer of gram positives