Prokaryotic Cell Structure and Function
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Questions and Answers

What is the primary function of fimbriae in prokaryotes?

  • To stick to their substrate or other individuals in a colony (correct)
  • To propel themselves by flagella
  • To allow for the exchange of DNA
  • To enable movement towards or away from a stimulus

    • Which of the following is NOT a factor contributing to genetic diversity in prokaryotes?

  • Rapid reproduction
  • Mutation
  • Binary fission (correct)
  • Genetic recombination

    • What is the name of the movement towards or away from a chemical stimulus?

  • Phototaxis
  • Flagellated movement
  • Taxis
  • Chemotaxis (correct)

    • What is the structure composed of a motor, hook, and filament that propels motile bacteria?

    <p>Flagella</p> Signup and view all the answers

    What is the term for the ability of bacteria to move towards or away from a stimulus?

    <p>Taxis</p> Signup and view all the answers

    What is the name of the region within prokaryotic cells where the circular chromosome is located?

    <p>Nucleoid region</p> Signup and view all the answers

    Which of the following is a characteristic of prokaryotic reproduction?

    <p>Binary fission</p> Signup and view all the answers

    What is the term for the metabolically inactive structures formed by some prokaryotes that can remain viable in harsh conditions?

    <p>Endospores</p> Signup and view all the answers

    Which of the following archaea thrive in very hot environments?

    <p>Extreme thermophiles (Clade Crenarchaeota)</p> Signup and view all the answers

    What is the primary function of chemoheterotrophic prokaryotes in ecosystems?

    <p>To break down dead organisms and waste products</p> Signup and view all the answers

    Which of the following bacteria are photoautotrophs that generate oxygen?

    <p>Cyanobacteria</p> Signup and view all the answers

    Which of the following is a characteristic of methanogens?

    <p>They are strict anaerobes and are poisoned by O2</p> Signup and view all the answers

    What is the primary function of prokaryotes in the recycling of chemical elements?

    <p>To increase the availability of nitrogen, phosphorus, and potassium</p> Signup and view all the answers

    Which of the following bacteria are helical heterotrophs?

    <p>Spirochetes</p> Signup and view all the answers

    Which of the following is an example of symbiosis?

    <p>Chlamydia living within animal cells</p> Signup and view all the answers

    What is the primary function of gram-positive bacteria such as Actinomycetes?

    <p>To decompose organic matter</p> Signup and view all the answers

    What is the process by which a prokaryotic cell takes up and incorporates foreign DNA from the surrounding environment?

    <p>Transformation</p> Signup and view all the answers

    Which of the following statements is true about conjugation in prokaryotes?

    <p>A donor cell attaches to a recipient by a pilus, pulls it closer, and transfers DNA</p> Signup and view all the answers

    What is the term for the movement of genes between bacteria by bacteriophages?

    <p>Transduction</p> Signup and view all the answers

    What is the term for the process by which some prokaryotes convert atmospheric nitrogen to ammonia?

    <p>Nitrogen fixation</p> Signup and view all the answers

    Which of the following modes of nutrition is characterized by the requirement of CO2 as a carbon source?

    <p>Autotrophs</p> Signup and view all the answers

    Which of the following statements is true about obligate anaerobes?

    <p>They are poisoned by O2 and use fermentation or anaerobic respiration</p> Signup and view all the answers

    What is the term for the exchange of metabolic products between photosynthetic cells and nitrogen-fixing cells in the cyanobacterium Anabaena?

    <p>Exchange of metabolic products</p> Signup and view all the answers

    Which of the following is a characteristic of facultative anaerobes?

    <p>They can survive with or without O2</p> Signup and view all the answers

    What is the primary function of the capsule in bacterial structure?

    <p>To enable binding to surfaces and evade phagocytosis</p> Signup and view all the answers

    Which bacterial structure is composed of a phospholipid bilayer with hydrophilic and hydrophobic regions?

    <p>Plasma membrane</p> Signup and view all the answers

    What is the main difference between gram-positive and gram-negative bacteria?

    <p>The composition of the cell wall</p> Signup and view all the answers

    What is the function of pili in bacterial structure?

    <p>To attach to surfaces and contribute to disease-causing ability</p> Signup and view all the answers

    What is the composition of the cell wall in bacterial structure?

    <p>Peptidoglycan</p> Signup and view all the answers

    What is the characteristic of gram-positive bacteria that enables binding to cell walls or recognition by macrophages?

    <p>Lipoteichoic acid</p> Signup and view all the answers

    What is the site of protein synthesis in bacterial cells?

    <p>Ribosomes</p> Signup and view all the answers

    What is the characteristic of bacterial DNA?

    <p>Circular and double-stranded</p> Signup and view all the answers

    What is the primary reason antibiotics have been effective in saving millions of lives from infections?

    <p>They target the specific bacteria that cause infection</p> Signup and view all the answers

    What is a consequence of using antibiotics in animal feed and water?

    <p>Evolution of resistant bacteria in animal populations that can spread to humans</p> Signup and view all the answers

    What is the main consequence of the overuse of antibiotics?

    <p>The evolution of antibiotic-resistant bacteria, or 'superbugs'</p> Signup and view all the answers

    Why should antibiotics be used judiciously?

    <p>To avoid driving the evolution of resistant bacteria</p> Signup and view all the answers

    What is the purpose of the Mega-Plate experiment?

    <p>To study how bacteria evolve resistance to antibiotics</p> Signup and view all the answers

    What is a limitation of using antibacterial chemicals in soaps and hand gels?

    <p>They can contribute to the problem of antibiotic resistance</p> Signup and view all the answers

    How do bacteria evolve resistance to antibiotics?

    <p>When bacteria with mutations that allow them to survive are the only ones left standing</p> Signup and view all the answers

    What did Alexander Fleming predict?

    <p>The development of antibiotic resistance</p> Signup and view all the answers

    What is the primary factor contributing to the rapid evolution of antibiotic resistance?

    <p>The fast reproduction rate of bacteria</p> Signup and view all the answers

    What is a key principle of responsible antibiotic use?

    <p>Using antibiotics to treat bacterial diseases only</p> Signup and view all the answers

    What is the outcome of the Mega-Plate experiment after 11 days?

    <p>The bacteria evolved from being susceptible to being highly resistant to antibiotics</p> Signup and view all the answers

    What is the primary function of the plasmid in bacterial genetics?

    <p>To encode for the sex pilus</p> Signup and view all the answers

    Which of the following processes involves the transfer of DNA from one bacterium to another through direct cell-to-cell contact?

    <p>Conjugation</p> Signup and view all the answers

    What is the term for the ability of bacteria to take up and incorporate foreign DNA from the environment?

    <p>Transformation</p> Signup and view all the answers

    Which of the following types of phages can give bacteria 'superpowers' such as the ability to produce exotoxins?

    <p>Lysogenic phages</p> Signup and view all the answers

    What is the primary function of the bacterial chromosome in bacterial genetics?

    <p>To store most of the bacterial DNA</p> Signup and view all the answers

    Which of the following processes involves the extraction of a small part of the bacterial chromosome to become a plasmid?

    <p>Transposition</p> Signup and view all the answers

    What is the term for the process by which a bacteriophage carrying its own DNA injects it into the bacterial DNA?

    <p>Transduction</p> Signup and view all the answers

    Which of the following bacteria are capable of taking up DNA from the environment and using it to gain new traits?

    <p>Streptococcus pneumoniae, H influenza, and Nesseria</p> Signup and view all the answers

    Which domain is characterized by the presence of histones, similar to Eukarya?

    <p>Archaea</p> Signup and view all the answers

    What is a common characteristic of Archaea and Eukarya during protein synthesis?

    <p>They use methionine as the start amino acid</p> Signup and view all the answers

    Which of the following is NOT a characteristic of domain Bacteria?

    <p>They are all extremophiles</p> Signup and view all the answers

    Which subgroup of Proteobacteria includes Rhizobium, which forms nodules on plant roots?

    <p>Alpha Proteobacteria</p> Signup and view all the answers

    What is the primary function of Cyanobacteria?

    <p>To produce their own sugar molecules using light and pigments</p> Signup and view all the answers

    Which of the following is a characteristic of Eukarya and Archaea?

    <p>They have similar RNA polymerase enzymes</p> Signup and view all the answers

    Which of the following is NOT a type of extremophile?

    <p>Phototrophs</p> Signup and view all the answers

    Which of the following domains is NOT closely related to Archaea?

    <p>Bacteria</p> Signup and view all the answers

    Study Notes

    Prokaryotic Cell Structure and Function

    • Prokaryotes have fimbriae, which allow them to stick to their substrate or other individuals in a colony.
    • Pili (or sex pili) are longer than fimbriae and allow prokaryotes to exchange DNA.
    • Prokaryotes exhibit taxis, the ability to move toward or away from a stimulus, including chemotaxis, movement toward or away from a chemical stimulus.
    • Most motile bacteria propel themselves by flagella, which are composed of a motor, hook, and filament.

    Prokaryotic Reproduction

    • Prokaryotes reproduce by binary fission, a process that takes 1-3 hours.
    • They have short generation times, which allows for rapid reproduction.
    • Many prokaryotes form metabolically inactive endospores, which can remain viable in harsh conditions for centuries.
    • Genetic diversity in prokaryotes arises from rapid reproduction, mutation, and genetic recombination.

    Domain Bacteria

    • Proteobacteria are gram-negative bacteria that include photoautotrophs, chemoautotrophs, and heterotrophs.
    • Chlamydia are parasites that live only within animal cells.
    • Spirochetes are helical heterotrophs, some of which are parasites.
    • Cyanobacteria are photoautotrophs that generate O2.
    • Gram-positive bacteria include actinomycetes, Bacillus anthracis, Clostridium botulinum, and some Staphylococcus and Streptococcus.

    Ecological Importance

    • Prokaryotes play a major role in the recycling of chemical elements between the living and nonliving components of ecosystems.
    • Chemoheterotrophic prokaryotes function as decomposers, breaking down dead organisms and waste products.
    • Prokaryotes can increase the availability of nitrogen, phosphorus, and potassium for plant growth.
    • Symbiosis is an ecological relationship in which two species live in close contact, including mutualism, commensalism, and parasitism.

    Genetic Recombination

    • Genetic recombination in prokaryotes occurs through transformation, transduction, and conjugation.
    • Transformation is the process of taking up and incorporating foreign DNA from the surrounding environment.
    • Transduction is the movement of genes between bacteria by bacteriophages (viruses that infect bacteria).
    • Conjugation is the process where genetic material is transferred between prokaryotic cells.

    Metabolism and Nutrition

    • Prokaryotes can be categorized by how they obtain energy and carbon, including phototrophs, chemotrophs, autotrophs, and heterotrophs.
    • Energy and carbon sources are combined to give four major modes of nutrition.
    • Nitrogen is essential for the production of amino acids and nucleic acids, and some prokaryotes can fix atmospheric nitrogen (N2) to ammonia (NH3).
    • Prokaryotic metabolism varies with respect to O2, including obligate aerobes, obligate anaerobes, and facultative anaerobes.

    Prokaryotic Diversity

    • Domain Archaea shares certain traits with bacteria and other traits with eukaryotes.
    • Some archaea live in extreme environments and are called extremophiles.
    • Methanogens are strict anaerobes and are poisoned by O2.
    • Domain Bacteria includes proteobacteria, chlamydia, spirochetes, cyanobacteria, and gram-positive bacteria.

    Bacteria Structure

    • Bacteria are found everywhere and are the largest group of microorganisms with medical significance.
    • They occur in three main shapes: coccus (circular), bacillus (rod-shaped), and spiral.
    • Some bacteria have a capsule, a polysaccharide-containing layer that allows them to bind to surfaces and evade phagocytosis.

    Bacterial Movement and Adhesion

    • Some bacteria have flagella, thin rigid filaments made of proteins that enable movement.
    • Bacteria can also possess hair-like appendages called fimbriae and pili, which help attach to surfaces and contribute to disease-causing ability.
    • Pili are involved in bacterial conjugation, the transfer of genetic material between bacteria.

    Bacterial Layers

    • The outermost layer is the capsule, composed of polysaccharides, which enables binding to cell surfaces and avoids phagocytosis.
    • The plasma membrane is a semi-permeable membrane allowing transportation of substances in and out of the cell.
    • The plasma membrane is composed of a phospholipid bilayer, similar to those found in human cells, with hydrophilic and hydrophobic regions.
    • The cell wall is a semi-rigid structure between the capsule and plasma membrane, composed of peptidoglycan.

    Gram-Positive and Gram-Negative Bacteria

    • Bacteria can be classified into two groups based on cell wall composition: gram-positive and gram-negative.
    • Gram-positive bacteria have a thick peptidoglycan layer and a cell membrane, while gram-negative bacteria have a thin peptidoglycan layer and an extra outer cell membrane.
    • Gram-positive bacteria have lipoteichoic acid, which enables binding to cell walls or recognition by macrophages.
    • Gram-negative bacteria have lipid-like structures on the outer cell membrane.

    Cytoplasm and Genetic Material

    • Cytoplasm contains water, enzymes, ribosomes, and circular DNA.
    • Ribosomes are the site of protein synthesis and are found throughout the cytoplasm.
    • The circular DNA is the genetic material of bacteria, different from the linear DNA found in human cells.
    • Plasmids, small circular genetic information, are found in the cytoplasm and can be transferred between bacteria through conjugation.

    Antibiotics and Bacteria

    • Antibiotics are natural substances produced by microbes to kill other microbes, and have been in use for billions of years
    • Alexander Fleming discovered penicillin in 1928, leading to the development of antibiotics that revolutionized medicine and saved millions of lives from infections

    The Problem with Antibiotics

    • Commercial antibiotics are "shock and awe" weapons, killing both bad and good bacteria in the gut
    • Overuse of antibiotics creates antibiotic-resistant bacteria, or "superbugs"
    • Misuse of antibiotics leads to the evolution of resistant bacteria

    The Mega-Plate Experiment

    • Scientists created a giant petri dish, the Mega-Plate, to study how bacteria evolve resistance to antibiotics
    • The experiment showed that E.coli bacteria can evolve from being susceptible to highly resistant to antibiotics in just 11 days

    How Antibiotic Resistance Evolves

    • Mutations in bacteria allow them to survive antibiotic exposure, and these mutants reproduce to create a population of super-resistant bugs
    • Fast reproduction rate of bacteria, such as E.coli, allows antibiotic resistance to evolve rapidly

    The Impact of Antibiotic Misuse

    • Antibiotics are used in animal feed and water to prevent livestock disease, leading to the evolution of resistant bacteria in animal populations
    • Resistant bacteria in animal populations can spread to humans, exacerbating the problem of antibiotic resistance
    • Alexander Fleming predicted the problem of antibiotic resistance due to overuse

    The Need for Responsible Antibiotic Use

    • Antibiotics should only be used to treat bacterial diseases, not viral diseases
    • Antibiotics should be used judiciously to avoid driving the evolution of resistant bacteria
    • Alternative approaches, such as antibacterial chemicals in soaps and hand gels, are not always effective and can contribute to the problem of antibiotic resistance

    Bacterial Genetics

    • Bacterial DNA consists of two parts: the large, complex bacterial chromosome containing most of the DNA, and the smaller, independent bacterial plasmid containing a small part of the DNA.

    Transposition

    • Transposition involves the extraction of a small part of the bacterial chromosome to form a plasmid, or the reintegration of a plasmid into the bacterial chromosome.
    • This process is related to plasmids, which are smaller and more accessible.

    Conjugation

    • Conjugation occurs between bacteria with a sex pilus (F+ bacteria) and those without (F- bacteria).
    • The sex pilus is encoded by the bacterial plasmid, not the bacterial chromosome.
    • During conjugation, F+ bacteria create a copy of their plasmid and transfer it to F- bacteria, resulting in both bacteria having a plasmid that encodes for a sex pilus.

    Transformation

    • Transformation, also known as competence, is the ability of bacteria to take up naked genomes or DNA from the environment and utilize it.
    • This process occurs exclusively in Streptococcus pneumoniae, H influenza, and Nesseria.
    • Through transformation, bacteria can acquire new traits, such as antibiotic resistance, by taking up DNA from their environment.

    Transduction

    • Transduction is the process in which a bacteriophage (bacterial virus) carrying its own DNA injects it into bacterial DNA.
    • The viral DNA integrates into the bacterial DNA and begins replicating the virus.
    • There are two types of bacteriophages: lytic phages, which result in bacterial death, and lysogenic phages, which do not.
    • Lysogenic phages can grant bacteria new abilities, such as the production of exotoxins, effectively giving them "superpowers".

    Phylogenetic Tree of Life

    • The phylogenetic tree represents three main domains of life: Eukarya, Archaea, and Bacteria.
    • Eukarya and Archaea share a common ancestor, making them sister taxa.
    • Bacteria is not closely related to Archaea, despite both being prokaryotic.

    Similarities between Archaea and Eukarya

    • Both have similar RNA polymerase enzymes.
    • Both have methionine as the start amino acid during protein synthesis.
    • Both have histones, which organize DNA.

    Domain Archaea

    • Archaea are extremophiles, thriving in extreme environments.
    • Examples of extremophiles include:
      • Halophiles, found in high-salinity environments like the Dead Sea and Great Salt Lake.
      • Thermofoils, found in high-temperature environments like hot springs and Yellowstone National Park.
      • Methanogens, found in oxygen-absent environments.

    Domain Bacteria

    • Bacteria are a widely diverse group found in many environments.
    • They perform beneficial functions for the environment and humans.
    • Some members of domain Bacteria cause diseases.
    • Subdivisions of domain Bacteria include:
      • Proteobacteria (gram-negative), a wide variety of microbes.
      • Chlamydia (gram-negative), mostly parasites that live within animal cells.
      • Spirochetes (gram-negative), helical-shaped bacteria responsible for diseases like Lyme disease.
      • Cyanobacteria, filamentous bacteria that produce sugar molecules using light and pigments like chlorophyll.
      • Gram-positive bacteria, including many examples like Bacillus, Clostridium, and Staphylococcus.

    Proteobacteria

    • Subgroups of Proteobacteria include:
      • Alpha Proteobacteria, including Rhizobium, which forms nodules on plant roots.
      • Beta Proteobacteria, including Nitrosomonas, a nitrogen-fixing bacterium.
      • Gamma Proteobacteria, including Pseudomonas fluorescens, a heterotroph.
      • Delta Proteobacteria, including bacteria that attack and destroy other bacteria.
      • Epsilon Proteobacteria, including Helicobacter pylori, associated with stomach ulcers.

    Other Bacteria

    • Chlamydia trachomatis is responsible for non-gonococcal urethritis, a common sexually transmitted disease.
    • Spirochetes have a helical shape and are responsible for diseases like Lyme disease.
    • Cyanobacteria include filamentous bacteria like Oscillatoria.
    • Gram-positive bacteria include Bacillus, Clostridium, and Staphylococcus, responsible for various diseases and having different characteristics.

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    Description

    This quiz covers the structure and function of prokaryotic cells, including fimbriae, pili, taxa, and flagella.

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