BIOL 2051 EXAM 1 Louisiana State University and
Agricultural & Mechanical College Questions with 100%
Verified Answers Latest Update
Question: A culture medium in which the precise chemical composition is known is classified
as:
Answer:
Defined medium
Question: Agar, the solidifying agent used in bacterial media, is extracted from which
organism?
Answer:
Rhodophyta (red algae)
Question: BSL1 organisms differ from BSL2 organisms in that:
Answer:
BSL1 organisms generally do not cause disease in healthy humans.
Question: During a culture transfer, where should the cap of the test tube be kept?
Answer:
Held in the same hand as the inoculating loop.
Question: Eosin Methylene Blue (EMB) agar differentiates bacteria based on their ability to:
Answer:
Ferment lactose
Question: Eosin Methylene Blue (EMB) agar selects for the growth of:
Answer:
Gram-negative bacteria
Question: Ethylene oxide is a gas chemosterilizer primarily used for:
Answer:
Sterilizing heat-sensitive objects like plastic Petri dishes
Question: If you are using a plastic culture tube, how does the aseptic procedure differ from
using a glass tube?
Answer:
,You should not pass the plastic tube through the flame.
Question: Ionizing radiation (such as X-rays and gamma rays) sterilizes by:
Answer:
Producing reactive ions that degrade biopolymers like DNA and proteins.
Question: Items sterilized in a hot-air oven generally require which conditions?
Answer:
170°C for 2 hours
Question: Mannitol Salt Agar (MSA) is selective because it selects for:
Answer:
Salt-tolerant organisms
Question: Microorganisms are described as "ubiquitous," which means:
Answer:
They are present nearly everywhere in the environment.
Question:
Answer:
Question: Nutrient Agar (NA) and Trypticase Soy Agar (TSA) are examples of which type of
media?
Answer:
Complex, general-purpose media
Question: On Mannitol Salt Agar (MSA) which has phenol red dye pH indicator, a color
change of the agar from red to yellow indicates:
Answer:
The organism ferments mannitol.
Question: Phenyl Ethyl Alcohol (PEA) agar is classified as:
Answer:
Selective only
Question: The currently accepted classification scheme for microorganisms is primarily
based on the analysis of which of the following?
, Answer:
16S ribosomal RNA (rRNA) gene sequences
Question: True or False: A differential medium provides a visible indication of a physiological
characteristic, such as carbohydrate fermentation.
Answer:
True
Question: True or False: According to the phylogenetic tree provided, viruses are considered
one of the three main domains of life.
Answer:
False
Question: True or False: Agar is a useful solidifying agent because it is readily broken down
and digested by most microbes as a nutrient source.
Answer:
False
Question: True or False: Dry heat primarily kills through oxidation, dehydration, and burning
of cellular components (proteins, nucleic acids), requiring higher temperature/longer times
because heat transfers less efficiently than moist heat, which works by coagulating proteins
at lower temperatures (like an autoclave).
Answer:
True
Question: True or False: Inoculating loops should be sterilized by flaming both before and
after the culture transfer.
Answer:
True
Question: True or False: Larger volumes of media take longer to reach sterilization
temperature in an autoclave than smaller volumes.
Answer:
True
Question:
Answer:
Question: True or False: Phenyl Ethyl Alcohol (PEA) agar allows Gram-negative organisms to
, grow while inhibiting Gram-positives.
Answer:
False
Question: True or False: Proper aseptic technique is necessary only in a clinical setting, not
in a student teaching laboratory.
Answer:
False
Question: True or False: UV radiation is an effective method for sterilizing media inside of
sealed, opaque plastic flasks.
Answer:
False
Question: True or False: When using a membrane filter for sterilization, the bacteria are
killed by the chemical composition of the filter paper.
Answer:
False
Question: Ultraviolet (UV) radiation kills microorganisms by:
Answer:
Causing damage to DNA by distorting the structure, specifically forming adjacent thymine
dimers.
Question: What are the standard conditions for moist heat sterilization using an autoclave?
Answer:
121°C at 15 psi for at least 15 minutes
Question: What is a major limitation of using UV radiation for sterilization?
Answer:
It cannot penetrate solid, opaque, light-absorbing surfaces.
Question: When performing aseptic transfers with a glass culture tube, which step is
essential to prevent contamination?
Answer:
Passing the neck of the tube briefly through a flame before and after the transfer.
Question: Which form of dry heat sterilization is commonly used in the lab for inoculating
Agricultural & Mechanical College Questions with 100%
Verified Answers Latest Update
Question: A culture medium in which the precise chemical composition is known is classified
as:
Answer:
Defined medium
Question: Agar, the solidifying agent used in bacterial media, is extracted from which
organism?
Answer:
Rhodophyta (red algae)
Question: BSL1 organisms differ from BSL2 organisms in that:
Answer:
BSL1 organisms generally do not cause disease in healthy humans.
Question: During a culture transfer, where should the cap of the test tube be kept?
Answer:
Held in the same hand as the inoculating loop.
Question: Eosin Methylene Blue (EMB) agar differentiates bacteria based on their ability to:
Answer:
Ferment lactose
Question: Eosin Methylene Blue (EMB) agar selects for the growth of:
Answer:
Gram-negative bacteria
Question: Ethylene oxide is a gas chemosterilizer primarily used for:
Answer:
Sterilizing heat-sensitive objects like plastic Petri dishes
Question: If you are using a plastic culture tube, how does the aseptic procedure differ from
using a glass tube?
Answer:
,You should not pass the plastic tube through the flame.
Question: Ionizing radiation (such as X-rays and gamma rays) sterilizes by:
Answer:
Producing reactive ions that degrade biopolymers like DNA and proteins.
Question: Items sterilized in a hot-air oven generally require which conditions?
Answer:
170°C for 2 hours
Question: Mannitol Salt Agar (MSA) is selective because it selects for:
Answer:
Salt-tolerant organisms
Question: Microorganisms are described as "ubiquitous," which means:
Answer:
They are present nearly everywhere in the environment.
Question:
Answer:
Question: Nutrient Agar (NA) and Trypticase Soy Agar (TSA) are examples of which type of
media?
Answer:
Complex, general-purpose media
Question: On Mannitol Salt Agar (MSA) which has phenol red dye pH indicator, a color
change of the agar from red to yellow indicates:
Answer:
The organism ferments mannitol.
Question: Phenyl Ethyl Alcohol (PEA) agar is classified as:
Answer:
Selective only
Question: The currently accepted classification scheme for microorganisms is primarily
based on the analysis of which of the following?
, Answer:
16S ribosomal RNA (rRNA) gene sequences
Question: True or False: A differential medium provides a visible indication of a physiological
characteristic, such as carbohydrate fermentation.
Answer:
True
Question: True or False: According to the phylogenetic tree provided, viruses are considered
one of the three main domains of life.
Answer:
False
Question: True or False: Agar is a useful solidifying agent because it is readily broken down
and digested by most microbes as a nutrient source.
Answer:
False
Question: True or False: Dry heat primarily kills through oxidation, dehydration, and burning
of cellular components (proteins, nucleic acids), requiring higher temperature/longer times
because heat transfers less efficiently than moist heat, which works by coagulating proteins
at lower temperatures (like an autoclave).
Answer:
True
Question: True or False: Inoculating loops should be sterilized by flaming both before and
after the culture transfer.
Answer:
True
Question: True or False: Larger volumes of media take longer to reach sterilization
temperature in an autoclave than smaller volumes.
Answer:
True
Question:
Answer:
Question: True or False: Phenyl Ethyl Alcohol (PEA) agar allows Gram-negative organisms to
, grow while inhibiting Gram-positives.
Answer:
False
Question: True or False: Proper aseptic technique is necessary only in a clinical setting, not
in a student teaching laboratory.
Answer:
False
Question: True or False: UV radiation is an effective method for sterilizing media inside of
sealed, opaque plastic flasks.
Answer:
False
Question: True or False: When using a membrane filter for sterilization, the bacteria are
killed by the chemical composition of the filter paper.
Answer:
False
Question: Ultraviolet (UV) radiation kills microorganisms by:
Answer:
Causing damage to DNA by distorting the structure, specifically forming adjacent thymine
dimers.
Question: What are the standard conditions for moist heat sterilization using an autoclave?
Answer:
121°C at 15 psi for at least 15 minutes
Question: What is a major limitation of using UV radiation for sterilization?
Answer:
It cannot penetrate solid, opaque, light-absorbing surfaces.
Question: When performing aseptic transfers with a glass culture tube, which step is
essential to prevent contamination?
Answer:
Passing the neck of the tube briefly through a flame before and after the transfer.
Question: Which form of dry heat sterilization is commonly used in the lab for inoculating
