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BIO250L LAB 5: EUKARYOTIC MICROBES,
PARASITOLOGY & VIRUSES – COMPLETE 2026
STUDY GUIDE WITH VERIFIED QUESTIONS & A+
RATIONALES
# PART I: PRE-LAB CONCEPTS (12 Questions)
**Question 1**
What is a model organism, and why is *Saccharomyces cerevisiae* (baker's yeast)
so often used as one in microbiology laboratories?
A) A model organism is a predator species used to control pest populations; *S.
cerevisiae* is used because it preys on bacteria
B) A model organism is a non-human species used to study biological processes
that can be applied to other organisms; *S. cerevisiae* is used due to its simple
genetics, rapid growth, low cost, and safety
C) A model organism is a type of pathogen used to test antibiotic effectiveness; *S.
cerevisiae* is used because it causes serious human disease
D) A model organism is a plant species used for agricultural research; *S.
cerevisiae* is a common crop pathogen
**Correct Answer: B**
**Rationale:** A model organism is a species that scientists study in the lab to
learn more about biological processes that often apply to other organisms,
including humans. *Saccharomyces cerevisiae* is an ideal model organism
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because it is inexpensive to grow, has a rapid growth rate, is safe to handle, and
shares many conserved cellular processes with complex eukaryotes, including
humans. It has been instrumental in understanding cell division, metabolism, and
genetics .
---
**Question 2**
Which of the following are beneficial properties of mold? (Select all that apply)
A) Production of antibiotics (e.g., penicillin from *Penicillium*)
B) Production of mycotoxins that cause food poisoning
C) Production of food products (e.g., cheese ripening, soy sauce fermentation)
D) Spoilage of stored grains and produce
**Correct Answer: A, C**
**Rationale:** Molds have both beneficial and harmful properties. Beneficial uses
include the production of antibiotics (penicillin) and the production of various
foods (cheese, soy sauce, tempeh) . Harmful properties include the production of
mycotoxins (aflatoxins) that cause illness, spoilage of food, and allergic reactions.
Options B and D describe harmful properties, not beneficial ones.
---
**Question 3**
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The lab guide discusses "acellular" organisms. What characteristics classify them
as acellular? Would you consider these living organisms?
A) Acellular organisms lack a nucleus but have other organelles; they are
considered fully living
B) Acellular organisms are composed of multiple cells arranged in a chain; they are
non-living
C) Acellular organisms have no cellular structure (no cell membrane, cytoplasm, or
organelles); they are generally NOT considered living because they cannot
reproduce or metabolize independently
D) Acellular organisms are prokaryotic bacteria; they are considered living
**Correct Answer: C**
**Rationale:** Acellular means "without cells." Acellular entities such as viruses,
viroids, and prions lack cellular structure—they have no cell membrane,
cytoplasm, or organelles. They are generally not considered living organisms
because they cannot reproduce, carry out metabolism, or maintain homeostasis
independently. They require a host cell to replicate .
---
**Question 4**
Describe an acellular organism other than viruses and prions discussed in the lab
materials.
A) Bacteria
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B) Protozoa
C) Viroids
D) Algae
**Correct Answer: C**
**Rationale:** Viroids are acellular infectious agents composed solely of a short
strand of circular single-stranded RNA without a protein coat. They are even
simpler than viruses and are known to cause diseases in plants. Like viruses and
prions, they lack cellular structure and cannot replicate independently .
---
**Question 5**
Which of the following statements about mold is TRUE?
A) All molds are pathogenic to humans
B) Molds are a type of bacteria that grow on bread
C) Molds are eukaryotic fungi that reproduce via spores and can be either
beneficial or harmful to humans
D) Molds are acellular organisms that require a host to replicate
**Correct Answer: C**
**Rationale:** Molds are eukaryotic fungi (not bacteria) that reproduce via spores.
They have both beneficial roles (antibiotic production, food production) and
BIO250L LAB 5: EUKARYOTIC MICROBES,
PARASITOLOGY & VIRUSES – COMPLETE 2026
STUDY GUIDE WITH VERIFIED QUESTIONS & A+
RATIONALES
# PART I: PRE-LAB CONCEPTS (12 Questions)
**Question 1**
What is a model organism, and why is *Saccharomyces cerevisiae* (baker's yeast)
so often used as one in microbiology laboratories?
A) A model organism is a predator species used to control pest populations; *S.
cerevisiae* is used because it preys on bacteria
B) A model organism is a non-human species used to study biological processes
that can be applied to other organisms; *S. cerevisiae* is used due to its simple
genetics, rapid growth, low cost, and safety
C) A model organism is a type of pathogen used to test antibiotic effectiveness; *S.
cerevisiae* is used because it causes serious human disease
D) A model organism is a plant species used for agricultural research; *S.
cerevisiae* is a common crop pathogen
**Correct Answer: B**
**Rationale:** A model organism is a species that scientists study in the lab to
learn more about biological processes that often apply to other organisms,
including humans. *Saccharomyces cerevisiae* is an ideal model organism
,2|Page
because it is inexpensive to grow, has a rapid growth rate, is safe to handle, and
shares many conserved cellular processes with complex eukaryotes, including
humans. It has been instrumental in understanding cell division, metabolism, and
genetics .
---
**Question 2**
Which of the following are beneficial properties of mold? (Select all that apply)
A) Production of antibiotics (e.g., penicillin from *Penicillium*)
B) Production of mycotoxins that cause food poisoning
C) Production of food products (e.g., cheese ripening, soy sauce fermentation)
D) Spoilage of stored grains and produce
**Correct Answer: A, C**
**Rationale:** Molds have both beneficial and harmful properties. Beneficial uses
include the production of antibiotics (penicillin) and the production of various
foods (cheese, soy sauce, tempeh) . Harmful properties include the production of
mycotoxins (aflatoxins) that cause illness, spoilage of food, and allergic reactions.
Options B and D describe harmful properties, not beneficial ones.
---
**Question 3**
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The lab guide discusses "acellular" organisms. What characteristics classify them
as acellular? Would you consider these living organisms?
A) Acellular organisms lack a nucleus but have other organelles; they are
considered fully living
B) Acellular organisms are composed of multiple cells arranged in a chain; they are
non-living
C) Acellular organisms have no cellular structure (no cell membrane, cytoplasm, or
organelles); they are generally NOT considered living because they cannot
reproduce or metabolize independently
D) Acellular organisms are prokaryotic bacteria; they are considered living
**Correct Answer: C**
**Rationale:** Acellular means "without cells." Acellular entities such as viruses,
viroids, and prions lack cellular structure—they have no cell membrane,
cytoplasm, or organelles. They are generally not considered living organisms
because they cannot reproduce, carry out metabolism, or maintain homeostasis
independently. They require a host cell to replicate .
---
**Question 4**
Describe an acellular organism other than viruses and prions discussed in the lab
materials.
A) Bacteria
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B) Protozoa
C) Viroids
D) Algae
**Correct Answer: C**
**Rationale:** Viroids are acellular infectious agents composed solely of a short
strand of circular single-stranded RNA without a protein coat. They are even
simpler than viruses and are known to cause diseases in plants. Like viruses and
prions, they lack cellular structure and cannot replicate independently .
---
**Question 5**
Which of the following statements about mold is TRUE?
A) All molds are pathogenic to humans
B) Molds are a type of bacteria that grow on bread
C) Molds are eukaryotic fungi that reproduce via spores and can be either
beneficial or harmful to humans
D) Molds are acellular organisms that require a host to replicate
**Correct Answer: C**
**Rationale:** Molds are eukaryotic fungi (not bacteria) that reproduce via spores.
They have both beneficial roles (antibiotic production, food production) and
