Bio205 CCS SU26 Microbiology (202620785) Cochise College
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Free Bio205 CCS SU26 Microbiology (202620785) Cochise College Questions
1.
______ phosphorylation in bacteria involves using energy from the electron transport chain to bond a phosphate group to ADP, forming ATP.
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Photo
-
Oxidative
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None of these are correct
-
Substrate level
Explanation
Explanation
Correct Answer: (B) Oxidative
Oxidative phosphorylation is the process by which ATP is synthesized using the energy generated from the electron transport chain. As electrons from NADH and FADH₂ are passed through a series of protein complexes in the membrane, protons are pumped across the membrane creating an electrochemical gradient. This proton motive force drives ATP synthase to bond an inorganic phosphate to ADP, producing ATP. In bacteria, this process occurs across the plasma membrane rather than in mitochondria as in eukaryotes, but the mechanism is functionally identical.
Why the other options are incorrect:
A. Photo — Photophosphorylation is the synthesis of ATP using light energy during photosynthesis. It also utilizes an electron transport chain, but the energy source is sunlight rather than the chemical energy released from oxidizing electron carriers like NADH and FADH₂. The question specifically describes energy from the electron transport chain driven by redox reactions, which defines oxidative phosphorylation.
C. None of these are correct — This is incorrect because oxidative phosphorylation precisely and completely describes the process defined in the question. A correct answer does exist among the options.
D. Substrate level — Substrate-level phosphorylation is the direct transfer of a phosphate group from a phosphorylated substrate molecule to ADP to form ATP. It does not involve the electron transport chain and occurs during glycolysis and the Krebs cycle. Since the question specifies energy from the electron transport chain, substrate-level phosphorylation is incorrect.
Correct Answer: (B) Oxidative
Oxidative phosphorylation is the process by which ATP is synthesized using the energy generated from the electron transport chain. As electrons from NADH and FADH₂ are passed through a series of protein complexes in the membrane, protons are pumped across the membrane creating an electrochemical gradient. This proton motive force drives ATP synthase to bond an inorganic phosphate to ADP, producing ATP. In bacteria, this process occurs across the plasma membrane rather than in mitochondria as in eukaryotes, but the mechanism is functionally identical.
Why the other options are incorrect:
A. Photo — Photophosphorylation is the synthesis of ATP using light energy during photosynthesis. It also utilizes an electron transport chain, but the energy source is sunlight rather than the chemical energy released from oxidizing electron carriers like NADH and FADH₂. The question specifically describes energy from the electron transport chain driven by redox reactions, which defines oxidative phosphorylation.
C. None of these are correct — This is incorrect because oxidative phosphorylation precisely and completely describes the process defined in the question. A correct answer does exist among the options.
D. Substrate level — Substrate-level phosphorylation is the direct transfer of a phosphate group from a phosphorylated substrate molecule to ADP to form ATP. It does not involve the electron transport chain and occurs during glycolysis and the Krebs cycle. Since the question specifies energy from the electron transport chain, substrate-level phosphorylation is incorrect.
2.
Which of the following statements about archaea is false?
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Some produce methane from carbon dioxide and hydrogen.
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They are prokaryotes.
-
They evolved before bacteria.
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They lack peptidoglycan in their cell walls.
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Some are thermoacidophiles; others are extreme halophiles.
Explanation
Explanation
Correct Answer: (C) They evolved before bacteria.
The claim that Archaea evolved before bacteria is not supported by current scientific evidence. Archaea and Bacteria are considered to have diverged from a common ancestral lineage very early in evolutionary history, and neither domain is definitively established to have preceded the other. This statement is therefore false.
Why the other options are incorrect:
A. Some produce methane from carbon dioxide and hydrogen — Methanogens are a well-characterized group of Archaea that produce methane through anaerobic metabolism. This is a true statement.
B. They are prokaryotes — Archaea are prokaryotic organisms that lack membrane-bound nuclei. This is a true and fundamental characteristic.
D. They lack peptidoglycan in their cell walls — Unlike bacteria, Archaea do not have peptidoglycan in their cell walls. Their walls may contain pseudopeptidoglycan or other unique polymers. This is a true statement.
E. Some are thermoacidophiles; others are extreme halophiles — Archaea are well known for thriving in extreme environments. Thermoacidophiles survive in hot acidic conditions and extreme halophiles live in very high-salt environments. This is a true statement.
Correct Answer: (C) They evolved before bacteria.
The claim that Archaea evolved before bacteria is not supported by current scientific evidence. Archaea and Bacteria are considered to have diverged from a common ancestral lineage very early in evolutionary history, and neither domain is definitively established to have preceded the other. This statement is therefore false.
Why the other options are incorrect:
A. Some produce methane from carbon dioxide and hydrogen — Methanogens are a well-characterized group of Archaea that produce methane through anaerobic metabolism. This is a true statement.
B. They are prokaryotes — Archaea are prokaryotic organisms that lack membrane-bound nuclei. This is a true and fundamental characteristic.
D. They lack peptidoglycan in their cell walls — Unlike bacteria, Archaea do not have peptidoglycan in their cell walls. Their walls may contain pseudopeptidoglycan or other unique polymers. This is a true statement.
E. Some are thermoacidophiles; others are extreme halophiles — Archaea are well known for thriving in extreme environments. Thermoacidophiles survive in hot acidic conditions and extreme halophiles live in very high-salt environments. This is a true statement.
3.
Viruses are not technically considered living organisms because they ______.
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are structurally very simple.
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can only be visualized using an electron microscope.
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are ubiquitous in nature.
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cannot reproduce by themselves.
-
are typically associated with disease.
Explanation
Explanation
Correct Answer: (D) Cannot reproduce by themselves.
One of the fundamental criteria for life is the ability to independently reproduce. Viruses lack the cellular machinery, including ribosomes, enzymes, and energy-producing organelles, necessary for self-replication. They can only reproduce by infecting a living host cell and hijacking its metabolic processes. Because they are entirely dependent on a host for replication and cannot carry out any metabolic activity independently, viruses do not meet the scientific criteria to be classified as living organisms.
Why the other options are incorrect:
A. Are structurally very simple — Structural simplicity alone does not exclude an entity from being classified as living. Many living organisms such as bacteria and archaea are structurally simple but are still considered alive.
B. Can only be visualized using an electron microscope — Size and visibility have no bearing on whether something is classified as living. Many living microorganisms also require microscopy for visualization.
C. Are ubiquitous in nature — Being widespread in nature is a characteristic shared by many living organisms and is not a criterion that determines whether something is classified as living or non-living.
E. Are typically associated with disease — Many living organisms including bacteria, fungi, and parasites cause disease. Disease association is irrelevant to the classification of something as living or non-living.
Correct Answer: (D) Cannot reproduce by themselves.
One of the fundamental criteria for life is the ability to independently reproduce. Viruses lack the cellular machinery, including ribosomes, enzymes, and energy-producing organelles, necessary for self-replication. They can only reproduce by infecting a living host cell and hijacking its metabolic processes. Because they are entirely dependent on a host for replication and cannot carry out any metabolic activity independently, viruses do not meet the scientific criteria to be classified as living organisms.
Why the other options are incorrect:
A. Are structurally very simple — Structural simplicity alone does not exclude an entity from being classified as living. Many living organisms such as bacteria and archaea are structurally simple but are still considered alive.
B. Can only be visualized using an electron microscope — Size and visibility have no bearing on whether something is classified as living. Many living microorganisms also require microscopy for visualization.
C. Are ubiquitous in nature — Being widespread in nature is a characteristic shared by many living organisms and is not a criterion that determines whether something is classified as living or non-living.
E. Are typically associated with disease — Many living organisms including bacteria, fungi, and parasites cause disease. Disease association is irrelevant to the classification of something as living or non-living.
4.
Treatment of disease with chemicals is called ______.
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chemo
-
medication
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antimicrobial therapy
-
chemotherapy
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All of these
Explanation
Explanation
Correct Answer Is:
D
In its broadest scientific definition, chemotherapy refers to the treatment of disease using chemical agents. While the term is commonly associated in clinical practice with cancer treatment, its original and technical meaning encompasses any use of chemical substances to treat disease, including antibiotics, antifungals, and antivirals. This broader definition originates from Paul Ehrlich's work in the early twentieth century developing chemical treatments for infectious diseases.
Why the other options are incorrect:
A. Chemo — Chemo is an informal abbreviation used colloquially to refer specifically to cancer chemotherapy. It is not the precise scientific term for chemical treatment of disease broadly.
B. Medication — Medication is a general term for any substance used to treat, cure, or prevent disease and is not specific to chemical-based disease treatment in the scientific sense.
C. Antimicrobial therapy — Antimicrobial therapy refers specifically to treatment targeting microorganisms such as bacteria, fungi, and viruses. It is a subcategory of chemotherapy, not a synonym for the broader concept.
E. All of these — While there is overlap among these terms in everyday usage, chemotherapy is the single most precise and scientifically accurate term for treatment of disease with chemicals as defined in microbiology and pharmacology.
Correct Answer Is:
D
In its broadest scientific definition, chemotherapy refers to the treatment of disease using chemical agents. While the term is commonly associated in clinical practice with cancer treatment, its original and technical meaning encompasses any use of chemical substances to treat disease, including antibiotics, antifungals, and antivirals. This broader definition originates from Paul Ehrlich's work in the early twentieth century developing chemical treatments for infectious diseases.
Why the other options are incorrect:
A. Chemo — Chemo is an informal abbreviation used colloquially to refer specifically to cancer chemotherapy. It is not the precise scientific term for chemical treatment of disease broadly.
B. Medication — Medication is a general term for any substance used to treat, cure, or prevent disease and is not specific to chemical-based disease treatment in the scientific sense.
C. Antimicrobial therapy — Antimicrobial therapy refers specifically to treatment targeting microorganisms such as bacteria, fungi, and viruses. It is a subcategory of chemotherapy, not a synonym for the broader concept.
E. All of these — While there is overlap among these terms in everyday usage, chemotherapy is the single most precise and scientifically accurate term for treatment of disease with chemicals as defined in microbiology and pharmacology.
5.
If the glycocalyx is firmly attached to the cell wall and well organized, it is called ______.
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a biofilm
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a capsule
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a flagellum
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a slime layer
Explanation
Explanation
The glycocalyx is the general term for the carbohydrate-rich coating found on the outside of many bacterial cells. When this coating is firmly and tightly attached to the cell wall and forms a well-organized, defined layer, it is specifically called a capsule. The capsule is a major virulence factor that protects bacteria from phagocytosis and desiccation.
Why the other options are incorrect:
A. A biofilm — A biofilm is a structured community of microorganisms encased in a self-produced matrix that adheres to a surface. While the glycocalyx contributes to biofilm formation, the term biofilm describes a community structure, not the organized attached glycocalyx of an individual cell.
C. A flagellum — A flagellum is a long, whip-like protein appendage used for bacterial motility. It is structurally and functionally entirely distinct from the glycocalyx.
D. A slime layer — A slime layer is also a form of glycocalyx, but it is loosely organized and not firmly attached to the cell wall, distinguishing it from the well-organized, tightly bound capsule.
The glycocalyx is the general term for the carbohydrate-rich coating found on the outside of many bacterial cells. When this coating is firmly and tightly attached to the cell wall and forms a well-organized, defined layer, it is specifically called a capsule. The capsule is a major virulence factor that protects bacteria from phagocytosis and desiccation.
Why the other options are incorrect:
A. A biofilm — A biofilm is a structured community of microorganisms encased in a self-produced matrix that adheres to a surface. While the glycocalyx contributes to biofilm formation, the term biofilm describes a community structure, not the organized attached glycocalyx of an individual cell.
C. A flagellum — A flagellum is a long, whip-like protein appendage used for bacterial motility. It is structurally and functionally entirely distinct from the glycocalyx.
D. A slime layer — A slime layer is also a form of glycocalyx, but it is loosely organized and not firmly attached to the cell wall, distinguishing it from the well-organized, tightly bound capsule.
6.
Which of the illustrations in Figure 1.1 has an axial filament?
-
a
-
b
-
c
-
d
-
e
Explanation
Explanation
Figure 1.1 illustration a shows a spirochete, which is a helically coiled bacterium. Spirochetes possess a unique internal motility structure called an axial filament, also known as periplasmic flagella. These flagella are located between the inner and outer membranes of the cell envelope and wrap around the cell body, causing the characteristic corkscrew-like rotation that propels the organism through viscous environments. Examples of spirochetes with axial filaments include Treponema pallidum and Borrelia burgdorferi.
Why the other options are incorrect:
B. b — Illustration b appears to show cocci, which are spherical bacteria. Cocci do not possess axial filaments and are non-motile in most cases.
C. c — Illustration c appears to show a chain of cocci such as streptococci. These organisms do not have axial filaments.
D. d — Illustration d appears to show a different bacterial morphology without the defining spirochete structure needed for axial filament presence.
E. e — Illustration e appears to show a bacterium with external flagella, which are standard external appendages distinct from the internal axial filament found in spirochetes.
Figure 1.1 illustration a shows a spirochete, which is a helically coiled bacterium. Spirochetes possess a unique internal motility structure called an axial filament, also known as periplasmic flagella. These flagella are located between the inner and outer membranes of the cell envelope and wrap around the cell body, causing the characteristic corkscrew-like rotation that propels the organism through viscous environments. Examples of spirochetes with axial filaments include Treponema pallidum and Borrelia burgdorferi.
Why the other options are incorrect:
B. b — Illustration b appears to show cocci, which are spherical bacteria. Cocci do not possess axial filaments and are non-motile in most cases.
C. c — Illustration c appears to show a chain of cocci such as streptococci. These organisms do not have axial filaments.
D. d — Illustration d appears to show a different bacterial morphology without the defining spirochete structure needed for axial filament presence.
E. e — Illustration e appears to show a bacterium with external flagella, which are standard external appendages distinct from the internal axial filament found in spirochetes.
7. Place the following taxonomic categories in order, from the most broad at the top, to the most specific at the bottom.
Genus, Phylum, Kingdom, Domain, Class, Order, Family, Species
Explanation
Explanation
Correct Answer (from most broad to most specific):
Domain → Kingdom → Phylum → Class → Order → Family → Genus → Species
The taxonomic hierarchy in biological classification, from broadest to most specific, is Domain, Kingdom, Phylum, Class, Order, Family, Genus, and Species. A helpful mnemonic to remember this order is: Dear King Philip Came Over For Good Soup. Each level becomes progressively more specific, with Domain encompassing the greatest diversity of life and Species representing the most precise and narrowly defined classification of an individual organism type.
Correct Answer (from most broad to most specific):
Domain → Kingdom → Phylum → Class → Order → Family → Genus → Species
The taxonomic hierarchy in biological classification, from broadest to most specific, is Domain, Kingdom, Phylum, Class, Order, Family, Genus, and Species. A helpful mnemonic to remember this order is: Dear King Philip Came Over For Good Soup. Each level becomes progressively more specific, with Domain encompassing the greatest diversity of life and Species representing the most precise and narrowly defined classification of an individual organism type.
8.
A microbe can perform both catabolic reactions that release energy and anabolic reactions that build molecules. Why might some metabolic pathways be described as amphibolic?
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They occur only when oxygen is absent.
-
They function in both catabolism and anabolism.
-
They involve only fermentation.
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They are unrelated to enzymes.
Explanation
Explanation
Correct Answer: (B) They function in both catabolism and anabolism.
Amphibolic pathways are metabolic pathways that serve dual roles, functioning in both catabolism and anabolism depending on the cell's needs. The citric acid cycle is the classic example. It can operate catabolically to break down acetyl-CoA and generate ATP, NADH, and FADH₂, but it also provides biosynthetic precursors such as alpha-ketoglutarate and oxaloacetate used in the synthesis of amino acids and other biomolecules. The term amphibolic comes from the Greek amphi meaning both sides.
Why Other Options are Incorrect:
A. They occur only when oxygen is absent — Amphibolic pathways such as the citric acid cycle are aerobic processes. Their amphibolic nature is not determined by oxygen availability.
C. They involve only fermentation — Fermentation is a strictly catabolic anaerobic process. Amphibolic pathways by definition serve both catabolic and anabolic functions and are not limited to fermentation.
D. They are unrelated to enzymes — All metabolic pathways, including amphibolic ones, are entirely enzyme-dependent. Enzymes catalyze every step of these reactions.
Correct Answer: (B) They function in both catabolism and anabolism.
Amphibolic pathways are metabolic pathways that serve dual roles, functioning in both catabolism and anabolism depending on the cell's needs. The citric acid cycle is the classic example. It can operate catabolically to break down acetyl-CoA and generate ATP, NADH, and FADH₂, but it also provides biosynthetic precursors such as alpha-ketoglutarate and oxaloacetate used in the synthesis of amino acids and other biomolecules. The term amphibolic comes from the Greek amphi meaning both sides.
Why Other Options are Incorrect:
A. They occur only when oxygen is absent — Amphibolic pathways such as the citric acid cycle are aerobic processes. Their amphibolic nature is not determined by oxygen availability.
C. They involve only fermentation — Fermentation is a strictly catabolic anaerobic process. Amphibolic pathways by definition serve both catabolic and anabolic functions and are not limited to fermentation.
D. They are unrelated to enzymes — All metabolic pathways, including amphibolic ones, are entirely enzyme-dependent. Enzymes catalyze every step of these reactions.
9.
What is the difference between a culture, a clone, and a strain?
Explanation
Explanation
A culture refers to microorganisms that are grown under controlled laboratory conditions in or on a nutrient medium. A culture can contain one or multiple types of microorganisms and serves as the general term for any laboratory-grown population of microbes.
A clone is a population of cells that are all genetically identical because they are all derived from a single parent cell through asexual reproduction. Clones represent exact genetic copies of the original organism and are used extensively in research and biotechnology to ensure genetic uniformity.
A strain is a subset or variant within a species that possesses distinct genetic or phenotypic characteristics that differentiate it from other members of the same species. Strains may differ in virulence, antibiotic resistance, antigenic properties, or metabolic capabilities. For example, Escherichia coli O157:H7 is a pathogenic strain that differs significantly from harmless E. coli strains found in normal gut flora.
In summary, a culture is a laboratory-grown microbial population, a clone is a genetically identical population derived from one cell, and a strain is a genetically distinct variant within a species.
A culture refers to microorganisms that are grown under controlled laboratory conditions in or on a nutrient medium. A culture can contain one or multiple types of microorganisms and serves as the general term for any laboratory-grown population of microbes.
A clone is a population of cells that are all genetically identical because they are all derived from a single parent cell through asexual reproduction. Clones represent exact genetic copies of the original organism and are used extensively in research and biotechnology to ensure genetic uniformity.
A strain is a subset or variant within a species that possesses distinct genetic or phenotypic characteristics that differentiate it from other members of the same species. Strains may differ in virulence, antibiotic resistance, antigenic properties, or metabolic capabilities. For example, Escherichia coli O157:H7 is a pathogenic strain that differs significantly from harmless E. coli strains found in normal gut flora.
In summary, a culture is a laboratory-grown microbial population, a clone is a genetically identical population derived from one cell, and a strain is a genetically distinct variant within a species.
10.
The third step of respiration is ______, which is where electrons are transferred from one compound to another to generate ATP energy. 2 ATP per ______, and 3 ATP per ______ are produced, which gives a net gain of ______ ATP.
-
The electron transport chain / FADH₂ / NADH / 34
-
Glycolysis / NADH / FADH₂ / 10
-
The Kreb's cycle / FADH₂ / NADH / 8
-
Fermentation / NADH / FADH₂ / 2
-
The electron transport chain / FADH₂ / NADH / 10
Explanation
Explanation
Correct Answer: (A) The electron transport chain / FADH₂ / NADH / 34
The third and final stage of aerobic respiration is the electron transport chain (ETC), located in the inner mitochondrial membrane in eukaryotes and the plasma membrane in prokaryotes. During the ETC, electrons from NADH and FADH₂ are passed through a series of protein complexes, releasing energy used to pump protons and drive ATP synthase through oxidative phosphorylation. Each FADH₂ feeds electrons into the chain at a lower point than NADH, generating approximately 2 ATP per FADH₂, while each NADH generates approximately 3 ATP. From the 10 NADH and 2 FADH₂ produced across all prior stages of respiration, the ETC yields approximately 34 ATP, bringing the total net ATP gain from complete aerobic respiration of one glucose molecule to approximately 36 to 38 ATP.
Why the other options are incorrect:
B. Glycolysis / NADH / FADH₂ / 10 — Glycolysis is the first stage, not the third. It produces only 2 net ATP and does not directly involve the electron transport chain or FADH₂.
C. The Kreb's cycle / FADH₂ / NADH / 8 — The Krebs cycle is the second stage of respiration. While it does produce FADH₂ and NADH, it generates only 2 ATP directly through substrate-level phosphorylation. It is not the stage where the bulk of ATP is produced through electron transfer.
D. Fermentation / NADH / FADH₂ / 2 — Fermentation is not a stage of aerobic respiration and does not involve the electron transport chain. It regenerates NAD⁺ anaerobically and produces only 2 net ATP total.
E. The electron transport chain / FADH₂ / NADH / 10 — While the stage and electron carrier assignments are correct, the net ATP yield of 10 is far too low. The ETC generates approximately 34 ATP from the electron carriers produced across all stages of aerobic respiration.
Correct Answer: (A) The electron transport chain / FADH₂ / NADH / 34
The third and final stage of aerobic respiration is the electron transport chain (ETC), located in the inner mitochondrial membrane in eukaryotes and the plasma membrane in prokaryotes. During the ETC, electrons from NADH and FADH₂ are passed through a series of protein complexes, releasing energy used to pump protons and drive ATP synthase through oxidative phosphorylation. Each FADH₂ feeds electrons into the chain at a lower point than NADH, generating approximately 2 ATP per FADH₂, while each NADH generates approximately 3 ATP. From the 10 NADH and 2 FADH₂ produced across all prior stages of respiration, the ETC yields approximately 34 ATP, bringing the total net ATP gain from complete aerobic respiration of one glucose molecule to approximately 36 to 38 ATP.
Why the other options are incorrect:
B. Glycolysis / NADH / FADH₂ / 10 — Glycolysis is the first stage, not the third. It produces only 2 net ATP and does not directly involve the electron transport chain or FADH₂.
C. The Kreb's cycle / FADH₂ / NADH / 8 — The Krebs cycle is the second stage of respiration. While it does produce FADH₂ and NADH, it generates only 2 ATP directly through substrate-level phosphorylation. It is not the stage where the bulk of ATP is produced through electron transfer.
D. Fermentation / NADH / FADH₂ / 2 — Fermentation is not a stage of aerobic respiration and does not involve the electron transport chain. It regenerates NAD⁺ anaerobically and produces only 2 net ATP total.
E. The electron transport chain / FADH₂ / NADH / 10 — While the stage and electron carrier assignments are correct, the net ATP yield of 10 is far too low. The ETC generates approximately 34 ATP from the electron carriers produced across all stages of aerobic respiration.
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