Bacterial Cell Structure and Function
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Questions and Answers

What is the average size range of bacteria?

  • 0.02 to 0.2 µm diameter × 0.2 to 0.8 µm length
  • 20 to 200 µm diameter × 20 to 80 µm length
  • 0.2 to 2.0 µm diameter × 2 to 8 µm length (correct)
  • 2 to 20 µm diameter × 20 to 80 µm length

    • What does the term 'monomorphic' refer to regarding bacteria?

  • Having a single shape (correct)
  • Existing only in pairs
  • Having multiple shapes
  • Lacking a defined shape

    • Which of the following is a spherical bacterial shape?

  • Bacillus
  • Spirillum
  • Vibrio
  • Coccus (correct)

    • Which of the following is a rod-shaped bacterial shape?

    <p>Bacillus (D)</p> Signup and view all the answers

    Which of the following describes bacteria in pairs?

    <p>Diplococci (B)</p> Signup and view all the answers

    What is the term for cubelike groups of eight bacteria?

    <p>Sarcinae (A)</p> Signup and view all the answers

    What is the movement of a solute from an area of high concentration to an area of low concentration called?

    <p>Simple diffusion (C)</p> Signup and view all the answers

    Which process requires a transporter protein and moves substances against their concentration gradient?

    <p>Active transport (C)</p> Signup and view all the answers

    What is the function of aquaporins in osmosis?

    <p>Creating water channels (A)</p> Signup and view all the answers

    In what type of solution does water move out of the cell?

    <p>Hypertonic solution (D)</p> Signup and view all the answers

    What is the name for the pressure needed to stop the movement of water across a membrane?

    <p>Osmotic pressure (D)</p> Signup and view all the answers

    What best describes the cytoplasm?

    <p>The substance inside the plasma membrane (D)</p> Signup and view all the answers

    What is the main component of cytoplasm?

    <p>Water (C)</p> Signup and view all the answers

    What is the role of plasmids in a bacterial cell?

    <p>Carry non-crucial genes like antibiotic resistance (D)</p> Signup and view all the answers

    What is the bacterial chromosome's shape?

    <p>Circular (C)</p> Signup and view all the answers

    What is the main function of ribosomes?

    <p>Protein synthesis (C)</p> Signup and view all the answers

    Which of the following is a component of the cytoskeleton?

    <p>Microfilaments (C)</p> Signup and view all the answers

    What is the function of the Golgi complex?

    <p>Protein modification and transport (B)</p> Signup and view all the answers

    Which structure is responsible for the selective permeability of the cell?

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

    Which of the following best describes the function of the smooth endoplasmic reticulum?

    <p>Cell membrane, fat, and hormone synthesis (D)</p> Signup and view all the answers

    What is the term for the fluid portion of the cytoplasm?

    <p>Cytosol (A)</p> Signup and view all the answers

    What does the nucleus contain?

    <p>DNA (D)</p> Signup and view all the answers

    What is endocytosis?

    <p>Engulfing solid or liquid into the cell (D)</p> Signup and view all the answers

    Where are 70S ribosomes found?

    <p>In chloroplasts and mitochondria (A)</p> Signup and view all the answers

    What is the name given to the movement of cytoplasm throughout a cell?

    <p>Cytoplasmic streaming (B)</p> Signup and view all the answers

    What percentage of a typical cell is composed of water?

    <p>80-90% (A)</p> Signup and view all the answers

    What happens to a cell in a hypertonic solution?

    <p>It shrinks. (C)</p> Signup and view all the answers

    What salt concentration is present in ocean water?

    <p>3.5% (B)</p> Signup and view all the answers

    Which of the following is a use of carbon for bacteria?

    <p>Structural backbone of organic molecules. (B)</p> Signup and view all the answers

    What is nitrogen used for in bacteria?

    <p>Component of proteins and DNA. (C)</p> Signup and view all the answers

    What is sulfur used for in bacteria?

    <p>Used in amino acids. (A)</p> Signup and view all the answers

    What is phosphorus used for in bacteria?

    <p>Used in DNA, RNA, and ATP. (A)</p> Signup and view all the answers

    What is the primary characteristic of aerotolerant anaerobes?

    <p>They tolerate oxygen but don't use it. (C)</p> Signup and view all the answers

    What is the function of trace elements in microbial growth?

    <p>They are used as enzyme cofactors. (C)</p> Signup and view all the answers

    What is required by obligate aerobes to live?

    <p>Oxygen (D)</p> Signup and view all the answers

    Which type of bacteria prefers to use oxygen but can grow in its absence?

    <p>Facultative anaerobes (D)</p> Signup and view all the answers

    What is quorum sensing in the context of biofilms?

    <p>Cell-to-cell communication (C)</p> Signup and view all the answers

    What is the purpose of using agar in culture media?

    <p>To solidify the culture media (B)</p> Signup and view all the answers

    Which type of bacteria is harmed by the presence of oxygen?

    <p>Obligate anaerobes (D)</p> Signup and view all the answers

    What is a key characteristic of chemically defined media?

    <p>The exact chemical composition is known. (C)</p> Signup and view all the answers

    Flashcards

    Prokaryote

    A unicellular organism without a membrane-bound nucleus.

    Eukaryote

    An organism whose cells contain a true nucleus.

    DNA location in prokaryotes

    Prokaryotes have DNA not enclosed in a membrane.

    DNA location in eukaryotes

    Eukaryotic DNA is contained within a nuclear membrane.

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    Types of bacterial shapes

    Bacteria can be bacillus, coccus, or spiral in shape.

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    Bacterial arrangements

    Bacteria can form pairs, chains, or clusters, like diplococci or staphylococci.

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    Binary fission

    The method by which prokaryotes divide to reproduce.

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    Simple diffusion

    Movement of a solute from high to low concentration until equilibrium is reached.

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    Facilitated diffusion

    Transport of solute via a transporter protein along the concentration gradient.

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    Osmosis

    Movement of water across a selectively permeable membrane from high to low water concentration.

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    Isotonic solution

    Solute concentrations are equal inside and outside the cell; water is at equilibrium.

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    Hypotonic solution

    Lower solute concentration outside the cell, causing water to move into the cell.

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    Hypertonic solution

    Higher solute concentration outside the cell, causing water to move out of the cell.

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    Active transport

    Movement against concentration gradient requiring a transporter protein and ATP.

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    Cytoplasm

    Substance inside the plasma membrane, mainly water with proteins, carbs, and ions.

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    Bacterial chromosome

    Circular DNA in the nucleoid carrying the cell's genetic information.

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    Aerotolerant Anaerobes

    Organisms that cannot use oxygen but can tolerate its presence.

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    Microaerophiles

    Organisms that require low concentrations of oxygen and are sensitive to high levels.

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    Biofilms

    Microbial communities forming slime that adhere to surfaces, sharing nutrients and shelter.

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    Culture Medium

    Nutrients prepared to support microbial growth.

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    Agar

    A complex polysaccharide used as a solidifying agent in culture media.

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    Osmotic Pressure

    The pressure required to stop water movement across a semipermeable membrane due to solute concentration.

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    Halophiles

    Microorganisms that require high salt concentrations for growth.

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    Obligate Halophiles

    Microbes that require very high salt concentrations (20-30%) to survive.

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    Facultative Halophiles

    Microbes that do not require high salt but can tolerate elevated levels (2% or more).

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    Carbon in Microbes

    Essential element for living organisms; used by chemoheterotrophs from organic molecules and by autotrophs from CO2.

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    Nitrogen Sources

    Nitrogen is crucial for proteins and nucleic acids; sourced from decomposing proteins or NH4+/NO3-.

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    Obligate Aerobes

    Organisms that require oxygen for survival and grow better with it.

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    Obligate Anaerobes

    Bacteria that cannot use oxygen and are harmed by its presence.

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    Plasma Membrane Structure

    A phospholipid bilayer with integral and peripheral proteins.

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    Sterols Function

    Complex lipids in membranes that resist lysis.

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    Carbohydrates in Membrane

    Used for attachment and cell-to-cell recognition.

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    Selective Permeability

    Ability of the membrane to control what enters and leaves the cell.

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    Endocytosis

    Process of engulfing solid or liquid into the cell.

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    Ribosomes Composition

    Sites of protein synthesis; 80S in eukaryotes, 70S in organelles.

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    Nucleus Structure

    Double membrane structure containing DNA and histones.

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    Endoplasmic Reticulum Types

    Rough ER has ribosomes for protein synthesis, Smooth ER synthesizes lipids.

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    Golgi Complex Function

    Modifies and transports proteins from the ER.

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    Study Notes

    Microbiology: Introduction

    • Microbiology is the study of microorganisms.
    • The book is titled "Microbiology: An Introduction," 12th Edition.
    • It is published by Pearson Education in 2016.

    Chapter 4: Functional Anatomy of Prokaryotic and Eukaryotic Cells

    • Prokaryote: Greek for "prenucleus."
    • Eukaryote: Greek for "true nucleus."
    • Prokaryotic cells lack a nucleus and other membrane-bound organelles.
    • Eukaryotic cells possess a nucleus and other membrane-bound organelles.

    Comparing Prokaryotic and Eukaryotic Cells

    • Prokaryote: single circular chromosome, no histones, no organelles, bacteria: peptidoglycan, archaea: pseudomurein, divides by binary fission.
    • Eukaryote: DNA in a nucleus, paired chromosomes, histones, organelles, simple cell walls when present, divides by mitosis.

    The Size, Shape, and Arrangement of Bacterial Cells

    • Average size: 0.2 to 2.0 µm diameter x 2 to 8 µm length.
    • Most bacteria are monomorphic (single shape).
    • A few are pleomorphic (many shapes).
    • Shapes include: Bacillus (rod-shaped), Coccus (spherical), Vibrio (curved rod), Spirillum (spiral), Spirochete (corkscrew-shaped), Star-shaped, and Rectangular.
    • Arrangements include: Pairs (diplococci, diplobacilli), Chains (streptococci, streptobacilli), Groups of four (tetrads), Cube-like groups of eight (sarcinae), and Clusters (staphylococci).

    Structure of a Prokaryotic Cell

    • Capsule: Outermost layer, viscous, gelatinous, made of polysaccharide and/or polypeptide.
    • Cell wall: Made of peptidoglycan, provides shape and protection against osmotic pressure.
    • Plasma membrane: Phospholipid bilayer, embedded proteins, selectively permeable. Functions include respiration, secretion, and transport.
    • Cytoplasm: Substance inside the plasma membrane, mostly water with proteins, carbohydrates, lipids, and ions. Cytoskeleton provides shape and structural support.
    • Ribosomes: Sites of protein synthesis (70S -- 50S + 30S subunits).
    • Nucleoid: Circular thread of DNA, the cell's genetic information.
    • Plasmids: Extrachromosomal genetic elements, carrying non-crucial genes.
    • Flagella: Filamentous appendages for movement (rotation or tumbling), made of flagellin.
    • Axial filaments: Found in spirochetes; internal flagella, corkscrew-like movement
    • Fimbriae and Pili: Hair-like appendages for attachment (colonization). Involved in motility, DNA transfer between cells (pilus).

    Gram-Positive and Gram-Negative Cell Walls

    • Gram-positive: Thick peptidoglycan layer, teichoic acids, susceptible to penicillin.
    • Gram-negative: Thin peptidoglycan layer, outer membrane, low susceptibility to penicillin, more susceptible to mechanical breakage.

    Atypical Cell Walls

    • Acid-fast cell walls: waxy lipid (mycolic acid) bound to peptidoglycan, stain with carbolfuchsin (Mycobacterium, Nocardia).
    • Mycoplasmas: Lack cell walls, sterols in plasma membrane (resist lysis).
    • Archaea: Wall-less, or walls of pseudomurein (lack NAM and D-amino acids).

    Eukaryotic Cells

    • Eukaryotes have a true nucleus and membrane-bound organelles.
    • Organelles include: Nucleus, Vacuole, Mitochondria, Chloroplasts, Endoplasmic Reticulum (rough and smooth), Golgi Complex, Lysosomes, Peroxisomes, Centrioles, Flaggella, Cilia.

    Flagella and Cilia

    • Flagella and cilia are projections used for locomotion or moving substances along the cell surface.
    • Flagella are long; cilia are short and numerous.
    • Both consist of microtubules made of protein tubulin; organized in a 9+2 array.

    The Cell Wall and Glycocalyx

    • Cell wall: Found in plants, algae, and fungi; made of carbohydrates (cellulose, chitin, glucan, mannan)
    • Glycocalyx: Carbohydrates bonded to proteins and lipids in the plasma membrane, found in animal cells, strengthens plasma membrane.

    The Plasma Membrane

    • Similar in structure to prokaryotic cell membranes (phospholipid bilayer, integral and peripheral proteins).
    • Differences include sterols (resist lysis) and carbohydrates (cell-to-cell recognition).
    • Similar in function to prokaryotic cell membranes (selective permeability, simple diffusion, facilitated diffusion, osmosis, and active transport).
    • Functions include endocytosis (engulfing solids/liquids) - phagocytosis (engulfing solids), pinocytosis (engulfing liquids/dissolved substances).

    Cytoplasm

    • Cytoplasm: the substance inside the plasma membrane and outside the nucleus.
    • Cytosol: The fluid portion of cytoplasm.
    • Cytoskeleton: composed of microfilaments and intermediate filaments; it gives shape and support to the cell.
    • Cytoplasmic streaming: movement of cytoplasm throughout the cell.

    Ribosomes

    • Sites of protein synthesis.
    • 80S: large 60S and small 40S subunit. Membrane-bound, attached to ER, or free in the cytoplasm
    • 70S: in chloroplasts and mitochondria

    The Nucleus

    • Double membrane structure (nuclear envelope) that contains the cell's DNA.
    • DNA is complexed with histone proteins to form chromatin.
    • During mitosis and meiosis, chromatin condenses into chromosomes.

    Endoplasmic Reticulum

    • Folded transport network.
    • Rough ER: studded with ribosomes; sites of protein synthesis.
    • Smooth ER: no ribosomes; synthesizes cell membranes, fats, and hormones.

    Golgi Apparatus

    • Transport organelle from the ER.
    • Modifies proteins from the ER.
    • Transports modified proteins via secretory vesicles to the plasma membrane.

    Mitochondria

    • Double membrane, inner folds (cristae) and fluid (matrix).
    • Involved in cellular respiration (ATP production).

    Chloroplasts

    • Locations of photosynthesis.
    • Contain flattened membranes (thylakoids) that contain chlorophyll.

    Organelles

    • Lysosomes: Vesicles formed in the Golgi complex, contain digestive enzymes.
    • Vacuoles: Cavities in the cell formed from the Golgi complex, bring food into cells, provide shape and storage.
    • Peroxisomes: Oxidize fatty acids; destroy H₂O₂.
    • Centrosomes: Networks of protein fibers and centrioles; form the mitotic spindle, critical role in cell division.

    Chapter 5: Microbial Metabolism

    • Metabolism: the buildup and breakdown of nutrients within a cell; provides energy and substances for life.
    • Catabolism: breaks down complex molecules, releases energy.
    • Anabolism: uses energy to build complex molecules.
    • Catabolism and anabolism linked by the availability of energy from ATP.
    • Enzymes: biological catalysts, speed up reactions, specific for certain substrates
    • Naming of enzymes (usually-ase ending) and basic aspects.
    • Holoenzymes: Apoenzyme (protein) and Cofactor (nonprotein), Coenzymes and co-factors role in enzyme activity
    • Factors influencing enzyme activity: Temperature (optima), pH (optima), Substrate concentration (saturation), Inhibitors (competitive and noncompetitive).
    • Feedback inhibition: end-product allosterically inhibits earlier enzymes in a pathway.
    • Ribozymes: RNA catalysts.
    • Oxidation-Reduction reactions: Oxidation (removal of electrons), Reduction (gain of electrons).
    • Bioenergetics: the study of energy that flows through a system.

    Metabolic Diversity Among Organisms

    • Phototrophs: use light energy.
    • Photoautotrophs: use light to fix carbon dioxide to sugar, such as oxygenic and anoxygenic photosynthesis
    • Photoheterotrophs: use light but need organic (external) carbon.
    • Chemoautotrophs: Use inorganic chemicals for energy; fix CO₂ to sugar.
    • Chemoheterotrophs: obtain energy and carbon from organic compounds like fermentation (e.g., lactic acid, alcohol).

    Chapter 6: Microbial Growth

    • Microbial growth: Increase in the number of cells, not cell size
    • Physical and chemical requirements for growth.
      • Temperature (optima), optimum pH, high osmotic pressure (plasmolysis) affect microbes greatly.
    • Different types of microbes (acidophiles, halophiles) require high osmotic pressures
    • Special factors (trace elements, essential nutrients, etc) required for proper microbial functioning.
    • Oxygen requirements in microbes: Oblige aerobes (need oxygen), facultative anaerobes (have oxygen but can grow without), Obligate anaerobes (harmed by oxygen).
    • Aerotolerant anaerobes tolerate oxygen but don't utilize it, while micro-aerophiles need oxygen in low concentration
    • Culture media (complex, chemically defined, and other kinds), important in microbial growth.
    • Media components, types, and functions.
    • Anaerobic growth media: reducing media to remove oxygen.
    • Techniques to obtain pure cultures: streak plate.
    • Methods of preserving bacterial cultures: deep-freezing, lyophilization.
    • Phases of bacterial growth: Four phases (lag, log, stationary, death).
    • Measurements of microbial growth: direct counts (plate/pour plate/spread methods, filtration, direct microscopic count) and indirect counts (turbidity, dry weight and metabolic activity methods) used in experimentation.
    • Specific types of media (selective, differential, enrichment media).

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    Description

    This quiz covers the fundamental aspects of bacterial structure, morphology, and function. Topics include bacterial shapes, solute movement, cytoplasm composition, the role of plasmids and ribosomes, and the characteristics of bacterial chromosomes. It is designed to test understanding of basic microbiology concepts.

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