Straighterline Microbiology BIO250 Final
Proctored Exam Review – DONE APRIL
2026 (QUESTIONS 1 – 60)
1. What microbial process was responsible for changing Earth’s atmosphere
from one without oxygen to one with oxygen?
A) Anaerobic respiration
B) Decomposition
C) Oxygenic photosynthesis
D) Temperature regulation
Rationale: Oxygenic photosynthesis, carried out by cyanobacteria and later by
algae and plants, used water as an electron donor and released oxygen as a
byproduct, fundamentally altering the planet’s atmosphere.
,2. In the nitrogen cycle, which of the following phases involves the release of
nitrogen as N₂ into the atmosphere?
A) Ammonification
B) Denitrification
C) Nitrification
D) Nitrogen fixation
Rationale: Denitrification is the process in which certain bacteria convert nitrate
(NO₃⁻) into nitrogen gas (N₂), which then returns to the atmosphere.
3. In the secondary phase of wastewater treatment, why is air injected into the
sludge as it is stirred and recirculated?
A) The air lowers the pH of the solution
B) The air keeps the sludge from clogging the pipes
C) Oxygen kills the bacteria in the water
D) The bioremediators need oxygen
Rationale: Many microorganisms used in secondary treatment are aerobic; they
require oxygen to efficiently break down organic matter in the sludge.
4. Which of the following microorganisms is used to make yogurt?
A) Lactobacillus bulgaricus
B) Penicillium roqueforti
C) Streptococcus lactis
D) Yeast
Rationale: Lactobacillus bulgaricus and Streptococcus thermophilus are the
primary starter cultures used in yogurt production, fermenting lactose to lactic acid.
5. ATP is a:
A) Lipid
B) Nucleotide
, C) Protein
D) Carbohydrate
Rationale: ATP (adenosine triphosphate) is a nucleotide that functions as the
primary energy currency of the cell, storing and releasing energy via hydrolysis of
its high-energy phosphate bonds.
6. Which of these are NOT considered a living organism?
A) Bacteria
B) Fungi
C) Protozoa
D) Viruses
Rationale: Viruses are acellular infectious agents that require a host cell to
replicate and lack cellular structures such as a cytoplasm, ribosomes, and a cell
membrane.
7. A viral capsid is composed of:
A) Lipids
B) Proteins
C) Nucleic acids
D) Polysaccharides
Rationale: The capsid is the protein shell that surrounds and protects the viral
genetic material; it is assembled from individual protein subunits called
capsomeres.
8. Which of the following describes the order in which different types of RNA
are involved in translation?
A) tRNA → rRNA → mRNA
B) mRNA → tRNA → rRNA
C) rRNA → mRNA → tRNA
D) mRNA → rRNA → tRNA
Proctored Exam Review – DONE APRIL
2026 (QUESTIONS 1 – 60)
1. What microbial process was responsible for changing Earth’s atmosphere
from one without oxygen to one with oxygen?
A) Anaerobic respiration
B) Decomposition
C) Oxygenic photosynthesis
D) Temperature regulation
Rationale: Oxygenic photosynthesis, carried out by cyanobacteria and later by
algae and plants, used water as an electron donor and released oxygen as a
byproduct, fundamentally altering the planet’s atmosphere.
,2. In the nitrogen cycle, which of the following phases involves the release of
nitrogen as N₂ into the atmosphere?
A) Ammonification
B) Denitrification
C) Nitrification
D) Nitrogen fixation
Rationale: Denitrification is the process in which certain bacteria convert nitrate
(NO₃⁻) into nitrogen gas (N₂), which then returns to the atmosphere.
3. In the secondary phase of wastewater treatment, why is air injected into the
sludge as it is stirred and recirculated?
A) The air lowers the pH of the solution
B) The air keeps the sludge from clogging the pipes
C) Oxygen kills the bacteria in the water
D) The bioremediators need oxygen
Rationale: Many microorganisms used in secondary treatment are aerobic; they
require oxygen to efficiently break down organic matter in the sludge.
4. Which of the following microorganisms is used to make yogurt?
A) Lactobacillus bulgaricus
B) Penicillium roqueforti
C) Streptococcus lactis
D) Yeast
Rationale: Lactobacillus bulgaricus and Streptococcus thermophilus are the
primary starter cultures used in yogurt production, fermenting lactose to lactic acid.
5. ATP is a:
A) Lipid
B) Nucleotide
, C) Protein
D) Carbohydrate
Rationale: ATP (adenosine triphosphate) is a nucleotide that functions as the
primary energy currency of the cell, storing and releasing energy via hydrolysis of
its high-energy phosphate bonds.
6. Which of these are NOT considered a living organism?
A) Bacteria
B) Fungi
C) Protozoa
D) Viruses
Rationale: Viruses are acellular infectious agents that require a host cell to
replicate and lack cellular structures such as a cytoplasm, ribosomes, and a cell
membrane.
7. A viral capsid is composed of:
A) Lipids
B) Proteins
C) Nucleic acids
D) Polysaccharides
Rationale: The capsid is the protein shell that surrounds and protects the viral
genetic material; it is assembled from individual protein subunits called
capsomeres.
8. Which of the following describes the order in which different types of RNA
are involved in translation?
A) tRNA → rRNA → mRNA
B) mRNA → tRNA → rRNA
C) rRNA → mRNA → tRNA
D) mRNA → rRNA → tRNA
