Formative Quiz #1 - Topic 1, 2, 3 Flashcards by Stephen George

What is an example of an inclusion body found in a bacterial cell?

a) Nucleus
b) Magnetosomes
c) Mitochondria
d) Polyhydroxybutyrate (PHB) granules
e) Cell membrane

d) Polyhydroxybutyrate (PHB) granules

Explanation: Inclusion bodies are not organelles but rather aggregates of peptides, carbohydrates, or other chemical compounds.

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How did the conditions of early Earth differ from today?

a) Less UV radiation due to excess volcanic activity
b) Limited O₂ availability and a reducing atmosphere
c) Lower temperatures and more ice coverage
d) Less methane, carbon dioxide, and nitrogen gas

b) Limited O₂ availability and a reducing atmosphere

Explanation: Early Earth was hot, had higher UV exposure, and its atmosphere contained more methane, carbon dioxide, and nitrogen gas.

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ABC transporters…

a) use a solute binding protein and a channel complex to transport nutrients across the membrane
b) are ATP-Binding Cassette transporters involved in passive transport
c) are examples of co-transport
d) are active transporters that move particles with their concentration gradients

a) use a solute binding protein and a channel complex to transport nutrients across the membrane

Explanation: ABC transporters use energy from ATP to transport specific substrates.

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Which of the following is NOT a characteristic of eukarya?

a) Nuclear membrane
b) Cell wall in some species
c) Having DNA replication enzymes similar to Archaea
d) Histones
e) Nucleoid

e) Nucleoid

Explanation: Eukaryotes contain a nucleus and share similarities with archaea but do not have a nucleoid.

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Which of the following is NOT a characteristic of bacteria?

a) Nuclear membrane
b) Cell wall
c) Single RNA polymerase
d) Histone-like proteins
e) DNA within a nucleoid

a) Nuclear membrane

Explanation: Bacteria lack a nuclear membrane; their genetic material is within a nucleoid.

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Why is lysozyme not effective against archaea?

a) The pseudopeptidoglycan in archaea has beta-1,3 linkages rather than beta-1,4, so the lysozyme is ineffective
b) The archaeal membrane is made up of different phospholipids, preventing lysozyme from entering
c) The N-acetylmuramic acid in archaea is structurally different and not susceptible to lysozyme
d) The lysozyme cannot lyse the ether bonds of archaeal phospholipids

a) The pseudopeptidoglycan in archaea has beta-1,3 linkages rather than beta-1,4, so the lysozyme is ineffective

Explanation: Lysozyme breaks beta-1,4 linkages, which archaea lack, making it ineffective.

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How did Pasteur disprove spontaneous generation?

a) By showing that bacteria would only grow when sterilized media was brought in direct contact with bacteria from the outside air
b) By showing that bacteria would grow in a sealed flask of sterile media
c) By showing that diseases were caused by bacteria
d) By isolating the infectious agent that caused disease

a) By showing that bacteria would only grow when sterilized media was brought in direct contact with bacteria from the outside air

Explanation: Pasteur’s experiments with swan-neck flasks demonstrated that microbial life does not spontaneously arise.

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Which of the following is NOT likely to be true of many primitive microorganisms?

a) Many were aerobic (using oxygen to breathe)
b) Some were photosynthetic
c) Many used reduced gases for energy
d) All had a plasma membrane
e) Many were thermophilic

a) Many were aerobic (using oxygen to breathe)

Explanation: Primitive microorganisms inhabited early Earth, which was hot and reducing with limited oxygen.

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Active regulation of the internal environment to maintain relative constancy is referred to as…

a) Homeostasis
b) Phylogeny
c) Biogeochemical cycling
d) Mutation

a) Homeostasis

Explanation: Homeostasis is the process of maintaining a stable internal environment despite external changes.

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Which of the following is not used to package bacterial DNA chromosomes?

a) Topoisomerases
b) Histones
c) Supercoiling
d) Cations

b) Histones

Explanation: Bacteria lack histones but do have histone-like proteins.

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Which process is more efficient for generating ATP from glucose?
a) Respiration, because it uses the TCA cycle to generate more ATP
b) Respiration, but it can only happen in mitochondria
c) Fermentation, because it does not require oxygen
d) Glycolysis, because it is faster and requires few reactions

a) Respiration, because it uses the TCA cycle to generate more ATP

Explanation: Respiration generates more ATP as it fully oxidizes glucose via the TCA cycle.

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Can cytoskeletal-like elements be found in archaea?
a) Yes, homologs of MreB (actin) have been found
b) Yes, homologs of FtsZ (tubulin) have been found
c) Yes, homologs of MreB, ParM, and FtsZ have been found
d) No, no cytoskeletal proteins have been found

a) Yes, homologs of MreB (actin) have been found

Explanation: Of these three, only one homolog has been found in archaea.

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Why is the term microbes more general than the term microorganisms?
a) It includes archaea
b) It includes fungus
c) There is no difference between these two terms
d) It includes viruses
e) The term microbes is just a more casual way of saying microorganisms

d) It includes viruses

Explanation: Microorganisms exclude viruses, but microbes include them.

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True or false: bacteria can sense their environment and move towards a particular substance.
a) False: bacteria can sense their environment but can only move randomly
b) True: bacteria effectively steer in the direction they wish to travel
c) True: bacteria use timing of runs and tumbles for chemotaxis
d) False: bacteria cannot sense their environment

c) True: bacteria use timing of runs and tumbles for chemotaxis

Explanation: Bacteria adjust their movement pattern using ‘runs and tumbles’ to move toward favorable environments.

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_____ is the study of the relationship between organisms.
a) Evolution
b) Phylogeny
c) Archaeology
d) Homology
e) Microbiology

b) Phylogeny

Explanation: Phylogeny studies the evolutionary relationships among organisms.

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Which of the following is NOT ALWAYS a characteristic of life?
a) Ability to respond to changes in the surrounding environment
b) Capacity to grow and evolve
c) Multicellularity
d) Ability to self-regulate and control the internal environment
e) None of the above

c) Multicellularity

Explanation: Bacteria and archaea are single-celled and still considered living.

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Peptidoglycan of Gram-positive bacteria is made of all these molecules except for which one?
a) Diaminopimelic acid (DAP)
b) D amino acids
c) N-acetylmuramic acid (NAM)
d) L amino acids
e) N-acetylglucosamine (NAG)

a) Diaminopimelic acid (DAP)

Explanation: DAP is found only in Gram-negative bacteria.

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True or false: archaeal cell walls are made of peptidoglycan.
a) True: it is similar to that found in Bacteria
b) False: the chemical composition is unknown
c) False: archaea use pseudomurein (or pseudopeptidoglycan)
d) True: but it is structurally different from that of Bacteria

c) False: archaea use pseudomurein (or pseudopeptidoglycan)

Explanation: Archaeal cell walls contain N-acetylglucosamine (NAG) and N-acetylalosaminuronic acid (NAT) to form pseudopeptidoglycan.

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Which of the following properties of archaea are more like eukaryotes than bacteria?

a) process of DNA replication
b) presence of histones
c) process of transcription
d) all of these choices

d) all of these choices

Explanation: Archaea share features like transcription and histones with eukaryotes.

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How did oxygenic photosynthetic microorganisms contribute to the evolution of metazoans (animals)?
a) They transformed inorganic material and made it available to other organisms
b) They consumed excess oxygen in the atmosphere left over from the great oxygenation event
c) They transformed Earth’s atmosphere from a reducing environment to an oxic environment
d) They were consumed and integrated into host cells through a process called endosymbiosis

c) They transformed Earth’s atmosphere from a reducing environment to an oxic environment

Explanation: This change allowed the evolution of complex, oxygen-dependent life forms.

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Most cells prefer to assimilate nitrogen as ammonia.
a) True
b) False

a) True

Explanation: ammonia (NH₃) is the most reduced form of nitrogen and is energetically favorable for incorporation into biomolecules.

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Saccharomyces:
a) Can reproduce asexually by merging two diploid cells
b) Forms a multicellular slug prior to sexual reproduction
c) Can reproduce sexually by undergoing meiosis and forming an ascus
d) Maintains a motile haploid state

c) Can reproduce sexually by undergoing meiosis and forming an ascus

Explanation: Saccharomyces, such as Saccharomyces cerevisiae (baker’s yeast), can reproduce both asexually and sexually. During sexual reproduction, two haploid cells of opposite mating types fuse to form a diploid zygote. The diploid cell then undergoes meiosis, producing four haploid spores that are enclosed in a structure called an ascus. This process ensures genetic diversity while maintaining the ability to survive during unfavorable conditions through spore formation.

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Which macromolecule is thought to have been the foundation for the first form of life?

a) Lipids and fatty acid chains forming micelles
b) Single-stranded catalytic DNA
c) Ribonucleic acid
d) Short catalytic peptides

c) Ribonucleic acid

Explanation: Catalytic RNA (ribozymes) are thought to be the foundation of early life because they can store genetic information and catalyze reactions, making them central to the RNA World Hypothesis.

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What role does crosslinking of the peptidoglycan molecules play in cell structure?

a) Helps in energy production
b) Provides strength to the peptidoglycan network
c) Regulates solute accessibility to the plasma membrane
d) Allows bacterial movement

b) Provides strength to the peptidoglycan network

Explanation: Crosslinking strengthens the peptidoglycan structure, maintaining bacterial cell integrity.

Which of the following is NOT used for bacterial classification? a) Method of motility b) Metabolic properties c) Environment they colonize d) Size and shape e) DNA sequence or genome

c) Environment they colonize Explanation: Bacteria inhabit nearly every environment, making it unreliable for classification.

Koch's postulates provide a framework for: a) Determining whether microorganisms developed spontaneously in nature b) Determining whether a microorganism causes a specific disease c) Determining the relatedness (e.g., phylogeny) of microorganisms d) Determining whether a microorganism can produce alcohol via fermentation

b) Determining whether a microorganism causes a specific disease Explanation: Koch's postulates establish causation between a microorganism and a disease.

Vibrio parahaemolyticus has which shape? a) Spiral b) Pleiomorphic c) Rod d) Spherical e) Curved rod

e) Curved rod Explanation: Vibrio species, including Vibrio parahaemolyticus, are characterized by their curved rod shape.

Fossilized ______________ are preserved marine structures that show ancient photosynthetic microbial life that contributed oxygen to the atmosphere over geological time. a) Stromatolites b) Microbialites c) Thrombolites d) Cyanobacteria

a) Stromatolites Explanation: Stromatolites are the earliest records of microbial life, dating back approximately 3.4 billion years.

Antonie van Leeuwenhoek was the first person to observe fruiting structures of mold using an early compound microscope. a) True b) False

b) False Explanation: While Leeuwenhoek made significant observations, the first person to observe fruiting structures of mold using a compound microscope was Robert Hooke.

What is an important function of some proteins within a cell? a) Catalyze chemical reactions b) Provide instructions for assembly of polypeptides c) Energy storage d) Information storage

a) Catalyze chemical reactions Explanation: Enzymatic proteins catalyze chemical reactions in the cell, speeding up processes such as metabolism, DNA replication, and cellular repair. This function is essential for maintaining life and enabling cellular functions to proceed efficiently.

Refers to bacteria with multiple flagella spread over the surface of the cell a) Polar b) Lophotrichous c) Monotrichous d) Amphitrichous e) Peritrichous

e) Peritrichous Explanation: Peritrichous bacteria have flagella distributed across their surface, aiding in movement.

What is the typical length of a bacterium? a) 5-10 mm b) 5-10 nm c) 20-40 μm d) 20-40 mm e) 0.5-5 μm

e) 0.5-5 μm Explanation: Most bacteria fall within the size range of 0.5-5 μm, though extreme examples exist.

What is the role of DNA for information flow within a cell? 1) Provides a template for translation 2) Provides a template for RNA replication 3) Provides a template for transcription 4) Provides a template for protein replication 5) None of the above.

3) Provides a template for transcription Explanation: Recall the central dogma: DNA ---> RNA ---> Protein You can think of it similarly for information flow: Replication(DNA-->DNA)-->Transcription (DNA-->RNA)-->Translation(RNA-->Protein)

How did the atmospheric oxygen concentration rise? 1) Via ancestors of the cyanobacteria 2) Via influx of oxygen from respiration 3) Via plants 4) By using the energy of the sun

1) Via ancestors of the cyanobacteria Explanation: Cyanobacteria are responsible for oxygenating the Earth's atmosphere through photosynthesis.

Region in bacterial and archaeal cells that contains the chromosomal DNA: 1) Nucleoid 2) Sulfur globules 3) Lysostaphin 4) Histone 5) Nucleus

1) Nucleoid Explanation: The nucleoid is the region in bacterial and archaeal cells where the chromosomal DNA is located, not enclosed by a membrane.

Which of the following properties of archaea are more like bacteria than eukaryotes? 1) Cell size 2) Cell shape 3) Chromosomal structure 4) All of these choices

4) All of these choices Explanation: Archaea share properties such as cell size, cell shape, and chromosomal structure with bacteria, distinguishing them from eukaryotes.

In bacteria, hopanoids are: 1) Histone-like proteins used to bind DNA and assist in supercoiling 2) Sterol-like molecules that help with membrane rigidity 3) Receptors on the outside of the cell used for chemotaxis 4) Channel proteins that shuttle hopanins across the membrane

2) Sterol-like molecules that help with membrane rigidity Explanation: Hopanoids are structural components of bacterial membranes, providing rigidity similar to sterols in eukaryotic cells.

Staphylococcus aureus has which shape? 1) Spiral 2) Curved rod 3) Rod 4) Spherical 5) Pleiomorphic

4) Spherical Explanation: Staphylococcus aureus is a spherical bacterium, classified as a coccus.

Which of the options below best describes 'aerotaxis'? 1) Morphological features that allow bacteria to become more aerodynamic and move faster towards energy sources 2) Movement of bacteria in response to different concentrations of oxygen 3) A taxonomic group of microorganisms that are tolerant to low oxygen concentrations 4) An evolutionary tradeoff in which oxygen is consumed for movement at the expense of ATP synthesis

2) Movement of bacteria in response to different concentrations of oxygen Explanation: Aerotaxis is the directed movement of bacteria toward or away from oxygen concentrations.

Endosymbiotic theory suggests: 1) Eukaryotes are descended from the merging of a bacterial and archaeal cell 2) Chloroplasts and mitochondria were once actually anaerobic bacteria 3) Over time, evolution selects symbioses that produce more complex organisms 4) Genetic traits are lost in the symbiont when they are no longer required by the host cell

1) Eukaryotes are descended from the merging of a bacterial and archaeal cell Explanation: Endosymbiotic theory explains how eukaryotic cells evolved from a symbiotic relationship between bacterial and archaeal cells.

Molecule used in co-transport in which the energy-requiring movement of one molecule is driven by the energetically favourable movement of another molecule in the opposite direction: 1) TonB receptors 2) Siderophores 3) Porins 4) ABC Transporters 5) Antiporters

5) Antiporters Explanation: Antiporters use the movement of one molecule down its gradient to drive the movement of another molecule against its gradient.

Which of the following is NOT a characteristic of archaea? 1) Nuclear membrane 2) Cell wall 3) Having a single RNA polymerase 4) Histones 5) Cytoplasmic membrane

1) Nuclear membrane Explanation: Archaea lack a nuclear membrane, archaea are prokaryotic and have their genetic material freely floating in the cytoplasm, distinguishing them from eukaryotes.

Which of the following is NOT a reason to use microbes as research models? 1) Some are easily cultivated in the lab 2) They have relatively large genomes 3) They can be easily genetically manipulated 4) They can facilitate production of enzymes and other proteins 5) All are true

2) They have relatively large genomes Explanation: Microbes are used as research models because of their small genomes, ease of cultivation, and genetic manipulability.

Which macromolecule is the least abundant in a microbial cell (in terms of dry weight)? 1) RNA 2) Polypeptides 3) DNA 4) Polysaccharides 5) Lipids

3) DNA Explanation: Polypeptides make up the majority of total cell mass, while DNA is the least abundant macromolecule in microbial cells.

The bacterial chromosome is a highly condensed structure that is tightly wound around itself to fit into the bacterial cell. What is the main enzyme responsible for condensing the DNA? 1) DNA ligase 2) DNA polymerase 3) DNA synthase 4) DNA endonuclease 5) DNA topoisomerase

5) DNA topoisomerase Explanation: DNA topoisomerases are enzymes that help manage DNA supercoiling, allowing the chromosome to fit inside the bacterial cell.

What is the likely origin of eukaryal mitochondria and chloroplasts? 1) Membrane invagination 2) Endosymbiosis of bacteria 3) Engulfment of other eukaryal cells 4) None of these choices 5) All of these choices.

2) Endosymbiosis of bacteria Explanation: Mitochondria and chloroplasts originated from bacterial cells that entered into symbiosis with eukaryal ancestors.

Why are beta-lactam antibiotics effective in killing bacteria? 1) They interfere with RNA synthesis 2) They interfere with cell membrane assembly 3) They punch holes in the cell membrane 4) They interfere with protein synthesis 5) They interfere with peptidoglycan crosslinking

5) They interfere with peptidoglycan crosslinking Explanation: Beta-lactam antibiotics disrupt the bacterial cell wall by inhibiting the enzymes responsible for peptidoglycan crosslinking.

How does the plasma membrane differ in composition between Archaea and Eukarya/Bacteria? 1) Archaeal membranes are made of isoprenoids connected to glycerol 1-P 2) Archaeal membranes are made of isoprenoids connected to glycerol 3-P 3) Archaeal membranes do not use lipids 4) Archaeal membranes use fatty acids connected to glycerol 1-P

1) Archaeal membranes are made of isoprenoids connected to glycerol 1-P Explanation: Archaeal membranes differ from those of Eukarya and Bacteria in that they are composed of isoprenoid chains (rather than fatty acids) linked to glycerol-1-phosphate via ether bonds. This unique structure makes archaeal membranes more stable and better adapted to extreme environmental conditions, such as high temperatures, salinity, or acidity, where many archaea thrive. This distinct composition also distinguishes them from the ester-linked fatty acid membranes found in Bacteria and Eukarya.

Which term describes straight rod-shaped bacteria? 1) Bacilli 2) Spirilla 3) Cocci 4) Pleiomorphic 5) Vibrios

1) Bacilli Explanation: Bacilli are straight rod-shaped bacteria, as opposed to other shapes like cocci (spherical) or spirilla (spiral).

Molecules in the Gram-positive cell wall that are attached to the plasma membrane: 1) Z-ring 2) Lipoteichoic acid 3) Flagella 4) Species 5) Lipid A

2) Lipoteichoic acid Explanation: Lipoteichoic acid is a molecule unique to Gram-positive bacteria. Embedded in the plasma membrane extending through the thick peptidoglycan layer of the cell wall. This structure helps anchor the cell wall to the plasma membrane, providing structural integrity. Playing a role in cell surface interactions, including adhesion and immune recognition. Lipoteichoic acids are also important for maintaining cell wall flexibility and ion homeostasis.

How does a mutation in the DNA cause a change in a protein's function? 1) The ribosomes cannot bind to the DNA and translate the protein 2) It doesn't, only mutations in RNA affect protein function 3) It doesn't, bacteria have several copies of proteins to protect against mutations that would limit function 4) It causes a change in the RNA, which changes the amino acid in the protein

4) It causes a change in the RNA, which changes the amino acid in the protein Explanation: A mutation in DNA alters the RNA sequence, which can result in a change to the amino acid sequence of the protein.

Why is bacterial and archaeal taxonomy experiencing rapid changes? 1) Improvements in electron microscopy have made it possible to see small differences in morphology between groups 2) There are more microbiologists than ever before, so more research is being produced 3) Sequencing technologies now allow for large genomic comparisons between microorganisms 4) We have developed better methods to investigate how microorganisms generate energy and grow (i.e., function)

3) Sequencing technologies now allow for large genomic comparisons between microorganisms Explanation: Advances in sequencing have revolutionized our understanding of bacterial and archaeal relationships.

Bacterial cells with a thin layer of peptidoglycan in the cell wall, surrounded by an outer membrane, which lose crystal violet stain in the Gram stain procedure and appear pink: 1) Gram variable 2) Outer membrane 3) Gram-positive 4) Gram-negative 5) S-layer

4) Gram-negative Explanation: Gram-negative bacteria appear pink in a Gram stain because their cell wall structure allows the crystal violet-iodine complex to be washed out during the alcohol decolorization step. This is primarily due to their **thin layer of peptidoglycan**, which is insufficient to retain the stain, and the presence of an **outer membrane**, which acts as a barrier. After decolorization, these cells take up the counterstain (safranin), giving them a pink appearance. In contrast, Gram-positive bacteria retain the crystal violet stain due to their thicker peptidoglycan layer.

What are the three domains of life? 1) Bacteria, Archaea, and Eukarya 2) Prokaryote, Eukaryote, and Archaea 3) Prokaryote, Eukaryote, and Fungi 4) Monera, Animals, and Plants 5) Animals, Plants, and Bacteria

1) Bacteria, Archaea, and Eukarya Explanation: The three-domain system—Bacteria, Archaea, and Eukarya—is based on phylogenetic analyses of molecular data, particularly ribosomal RNA sequencing, to reflect evolutionary relationships. The term "Prokaryote" in option 2 is not a domain but a general term for organisms without a nucleus, encompassing both Bacteria and Archaea, which are distinct domains in this system. This distinction recognizes the fundamental differences between Bacteria and Archaea, such as cell membrane composition, genetic machinery, and metabolic pathways.

The cytoplasm of a bacterium contains all of these features except for which one? 1) DNA 2) Cytoskeleton 3) Mitochondria 4) Ribosomes 5) RNA

3) Mitochondria Explanation: Mitochondria are exclusive to eukaryotes and are not found in the cytoplasm of bacterial cells.

This early microbiology pioneer developed a set of criteria for linking a specific microorganism to a specific disease: 1) John Tyndall 2) Anton van Leeuwenhoek 3) Robert Koch 4) Louis Pasteur 5) Edward Jenner

3) Robert Koch Explanation: Robert Koch developed postulates linking specific microorganisms to diseases, a foundation of microbiology.

Pili (as a general term) can perform many functions for bacteria, but NOT _________________. 1) Adherence to surfaces 2) Sex 3) Nutrient absorption 4) Adherence to host cells 5) Twitching motility

3) Nutrient absorption Explanation: Pili are surface structures that aid in adherence, motility, and DNA transfer, but they are not involved in nutrient absorption.

What is an autotroph? 1) An organism that ingests organic molecules 2) An organism that can produce its own organic molecules from inorganic carbon 3) An organism that produces organic molecules via photosynthesis

2) An organism that can produce its own organic molecules from inorganic carbon Explanation: Autotrophs generate organic molecules by utilizing inorganic carbon sources such as CO₂