Prokaryotic vs. Eukaryotic Cells
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Questions and Answers

Which of the following cellular structures is found in both prokaryotic and eukaryotic cells?

  • Endoplasmic reticulum
  • Mitochondria
  • Plasma membrane (correct)
  • Nucleus

A scientist discovers a new microorganism. Initial observations reveal that its cells lack a nucleus. To which domain does this organism likely belong?

  • Plantae
  • Bacteria (correct)
  • Eukarya
  • Animalia

Which of the following statements correctly describes the organization of genetic material in prokaryotic and eukaryotic cells?

  • Prokaryotic cells have a single, circular chromosome located in a nucleoid, while eukaryotic cells have multiple, rod-shaped chromosomes within a nucleus. (correct)
  • Both cell types contain genetic material in the form of plasmids.
  • Eukaryotic cells have a single, circular chromosome located in a nucleoid, while prokaryotic cells have linear chromosomes within a nucleus.
  • Both cell types have multiple, linear chromosomes stored within a nucleus.

A researcher is studying a cell under a microscope and observes numerous membrane-bound organelles. Which conclusion can they confidently make?

<p>The cell is eukaryotic and could be either a plant or animal cell. (D)</p> Signup and view all the answers

In eukaryotic cells, compartmentalization due to membrane-bound organelles is essential for which of the following reasons?

<p>To separate and optimize different biochemical processes. (D)</p> Signup and view all the answers

Although prokaryotic cells lack membrane-bound organelles, how do they compartmentalize their cytoplasm?

<p>By utilizing inclusions to segregate specific substances or reactions. (A)</p> Signup and view all the answers

A new drug is designed to inhibit protein synthesis by targeting ribosomes. If this drug is effective, which type(s) of cells would be affected?

<p>Both prokaryotic and eukaryotic cells (B)</p> Signup and view all the answers

Which of the following features is unique to prokaryotic cells and not found in eukaryotic cells?

<p>Presence of a nucleoid region (A)</p> Signup and view all the answers

Which aspect of bacterial pili is NOT explicitly mentioned in the provided content?

<p>Genetic regulation of pilus expression (C)</p> Signup and view all the answers

Based on the information provided, what is a key focus of research regarding E. coli common pili?

<p>Understanding the structural aspects related to biogenesis and biofilm formation. (D)</p> Signup and view all the answers

What type of bacteria are discussed in the context of pili structure and function?

<p>Both Gram-positive and Gram-negative bacteria. (D)</p> Signup and view all the answers

Which of the following can be inferred about the role of pili from the provided information?

<p>Pili play a significant role in the pathogenesis of bacterial infections. (A)</p> Signup and view all the answers

OpenStax utilizes which Creative Commons license for their textbook content?

<p>Creative Commons Attribution License (D)</p> Signup and view all the answers

What is the primary function of the cell wall in prokaryotic cells?

<p>Maintaining cell shape and protecting against osmotic pressure changes. (A)</p> Signup and view all the answers

A prokaryotic cell is placed in a hypertonic solution. What is the likely outcome for the cell?

<p>The cell membrane will detach from the cell wall, leading to plasmolysis. (D)</p> Signup and view all the answers

Which of the following best describes the organization of genetic material in prokaryotic cells?

<p>A single, circular chromosome located in the nucleoid region, along with potential plasmids. (C)</p> Signup and view all the answers

What is the role of nucleoid-associated proteins (NAPs) in prokaryotic cells?

<p>Assisting in the organization and packaging of the chromosome. (D)</p> Signup and view all the answers

Plasmids often carry genes that provide which of the following advantageous traits to prokaryotic cells?

<p>Resistance to antibiotics. (A)</p> Signup and view all the answers

How do prokaryotic ribosomes differ from eukaryotic ribosomes in terms of structure and location?

<p>Prokaryotic ribosomes are 70S and located in the cytoplasm , while eukaryotic ribosomes are 80S and found in the cytoplasm. (D)</p> Signup and view all the answers

What is the primary benefit of storing nutrients in a polymerized form within inclusions?

<p>It reduces the osmotic pressure buildup from accumulating solutes. (D)</p> Signup and view all the answers

If a prokaryotic cell lacking a cell wall is placed in a hypotonic solution, what is the most likely outcome?

<p>The cell will swell and lyse. (A)</p> Signup and view all the answers

Which of the following is a key difference between bacterial and archaeal ribosomes?

<p>Archaeal ribosomes are more similar to eukaryotic ribosomes than to bacterial ribosomes. (C)</p> Signup and view all the answers

A cell is observed to have undergone plasmolysis. What can be inferred about the cell's environment?

<p>The cell is in a hypertonic environment. (D)</p> Signup and view all the answers

What is the significance of the distinctive arrangements formed when prokaryotic cells of the same species group together?

<p>These arrangements, along with cellular shape, can be characteristic of certain species. (D)</p> Signup and view all the answers

Which of the following cellular structures is NOT directly involved in protecting a prokaryotic cell from osmotic stress?

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

Which statement correctly describes how the tonicity of a solution affects a prokaryotic cell with a cell wall?

<p>In a hypertonic solution, the cell membrane detaches from the cell wall, preventing lysis through plasmolysis. (D)</p> Signup and view all the answers

How does the presence of plasmids contribute to the adaptability of prokaryotic cells?

<p>By carrying genes that can confer advantageous traits such as antibiotic resistance. (C)</p> Signup and view all the answers

What would be the most likely consequence of a mutation that impairs the function of NAPs in a bacterium?

<p>Disrupted chromosome organization leading to impaired DNA replication and gene expression. (D)</p> Signup and view all the answers

Which of the following best describes the function of volutin granules found in some microorganisms?

<p>Storing polymerized inorganic phosphate for metabolism and biofilm formation. (C)</p> Signup and view all the answers

Magnetosomes are inclusions found in magnetotactic bacteria that enable what function?

<p>Alignment and movement along magnetic fields. (C)</p> Signup and view all the answers

Which of the following is NOT a characteristic of endospores that contributes to their survival in harsh conditions?

<p>A metabolically active state allowing for rapid response to environmental changes. (A)</p> Signup and view all the answers

What is the primary function of carboxysomes found in certain prokaryotic cells?

<p>To compartmentalize enzymes involved in carbon metabolism. (A)</p> Signup and view all the answers

The process of sporulation in bacteria is typically triggered by what environmental condition?

<p>Depletion of nutrients or other unfavorable conditions. (D)</p> Signup and view all the answers

Which of the following is a key distinction between archaeal and bacterial/eukaryotic cell membranes?

<p>Archaea have branched chain phospholipids, while bacteria and eukaryotes have straight-chained phospholipids. (B)</p> Signup and view all the answers

Which of the following bacterial genera are known for their ability to form endospores?

<p><em>Bacillus</em> and <em>Clostridium</em>. (A)</p> Signup and view all the answers

What is the role of the septum during the process of sporulation?

<p>To divide the cell asymmetrically, forming a DNA forespore. (B)</p> Signup and view all the answers

How do glycoproteins and glycolipids contribute to a cell's interaction with its environment?

<p>They extend from the cell surface, enabling interaction with the external environment. (C)</p> Signup and view all the answers

What is the 'fluid mosaic model' used to describe in the context of cell membranes?

<p>The ability of membrane components to move fluidly within the membrane and the mosaic-like composition of lipids and proteins. (B)</p> Signup and view all the answers

Phospholipid-derived fatty acid analysis (PLFA) is a valuable technique because it can:

<p>identify unique species based on differences in fatty acids. (A)</p> Signup and view all the answers

Which of the following best describes the composition of the plasma membrane in most bacterial cells?

<p>A bilayer composed mainly of phospholipids formed with ester linkages and proteins. (D)</p> Signup and view all the answers

A cell needs to transport a large, polar molecule across its plasma membrane down its concentration gradient. Which transport mechanism would be most appropriate?

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

What is the primary distinction between active and passive transport processes?

<p>Active transport requires energy input, while passive transport does not. (D)</p> Signup and view all the answers

How do gas vacuoles contribute to the survival of prokaryotic cells that possess them?

<p>By allowing cells to adjust their buoyancy and location in the water column. (D)</p> Signup and view all the answers

How does the presence of a phospholipid monolayer around PHB inclusions benefit the bacteria?

<p>It protects PHB from degradation and regulates its usage. (A)</p> Signup and view all the answers

What is unique about group translocation as a transport mechanism?

<p>It modifies the transported molecule chemically as it crosses the membrane. (C)</p> Signup and view all the answers

What is the key event that marks the end of sporulation and the release of the endospore?

<p>The disintegration of the mother cell. (B)</p> Signup and view all the answers

What is the role of thylakoids, chromatophores, lamellae, and chlorosomes in photosynthetic prokaryotes?

<p>They enclose photosynthetic pigments and enable photosynthesis. (C)</p> Signup and view all the answers

Why is peptidoglycan an effective target for antibacterial drugs?

<p>It is unique to bacterial cell walls. (B)</p> Signup and view all the answers

Which of the following characteristics distinguishes vegetative cells from endospores?

<p>Vegetative cells are actively growing and dividing. (C)</p> Signup and view all the answers

Which of the following describes the process of germination in endospores?

<p>The cell re-enters a vegetative state and becomes metabolically active. (C)</p> Signup and view all the answers

How do human immune cells recognize and destroy bacterial pathogens?

<p>By recognizing peptidoglycan on the bacterial cell surface. (D)</p> Signup and view all the answers

What is the significance of inclusions like carboxysomes being referred to as 'proto-organelles'?

<p>They compartmentalize important compounds or chemical reactions, similar to eukaryotic organelles. (A)</p> Signup and view all the answers

What is the role of peptide bridges within peptidoglycan?

<p>They provide two-dimensional tensile strength to the cell wall. (B)</p> Signup and view all the answers

In Gram-positive bacteria, what connects the tetrapeptide chains extending from NAM units in peptidoglycan?

<p>Pentaglycine cross-bridges (D)</p> Signup and view all the answers

How does the phosphotransferase system contribute to bacterial sugar metabolism?

<p>It phosphorylates sugars upon entry into the cell, facilitating their metabolism. (B)</p> Signup and view all the answers

A bacterium is found to be resistant to lysozyme. Which structural component of the cell is likely providing this resistance?

<p>A modified cell wall (D)</p> Signup and view all the answers

A researcher discovers a new species of bacteria that thrives in extremely hot environments. What adaptation might be present in its membrane to maintain fluidity at such high temperatures?

<p>A high proportion of phospholipids with longer, saturated fatty acids (C)</p> Signup and view all the answers

A scientist is studying a bacterial species and observes that it can survive in both isotonic and hypotonic solutions, but not in hypertonic solutions. What is the most likely explanation for this?

<p>The bacteria have a rigid cell wall that prevents collapse and swelling, but cannot prevent plasmolysis. (C)</p> Signup and view all the answers

Which of the following is the primary function of fimbriae in pathogenic bacteria?

<p>Aiding in adherence to host cells for colonization and infectivity. (D)</p> Signup and view all the answers

How does the arrangement of flagella contribute to the directional movement of bacteria in response to a chemical attractant?

<p>By increasing the length of runs and decreasing the length of tumbles. (C)</p> Signup and view all the answers

Rebecca Lancefield's serotyping method primarily utilized which bacterial cell envelope characteristic to classify Streptococcus species?

<p>Specific cell-surface antigens. (A)</p> Signup and view all the answers

What role does the M protein play in the virulence of Group A Streptococcus?

<p>It helps the bacteria evade the host's immune system. (C)</p> Signup and view all the answers

Which of the following bacterial species is characterized by a monotrichous flagellum arrangement?

<p><em>Vibrio cholerae</em>. (D)</p> Signup and view all the answers

How do bacterial flagella enable movement in aqueous environments?

<p>By functioning as propellers that spin to move the cell. (D)</p> Signup and view all the answers

What structural feature differentiates the basal body of flagella in Gram-positive and Gram-negative bacteria?

<p>Differences in cell wall structure. (D)</p> Signup and view all the answers

Why are the terms fimbriae and pili often used interchangeably?

<p>Because differentiation between the two is problematic. (B)</p> Signup and view all the answers

Which bacterial species displays a lophotrichous flagella arrangement?

<p><em>Pseudomonas aeruginosa</em>. (B)</p> Signup and view all the answers

What is the function of the F pilus (sex pilus)?

<p>To transfer DNA between bacterial cells. (A)</p> Signup and view all the answers

In a bacterium with peritrichous flagella, how are the flagella arranged during a 'run'?

<p>They are bundled together in a streamlined way. (B)</p> Signup and view all the answers

What environmental signal do magnetosomes enable bacteria to respond to?

<p>Magnetic fields. (D)</p> Signup and view all the answers

Which of the following is an example of a bacterium with amphitrichous flagella?

<p><em>Spirillum minor</em>. (A)</p> Signup and view all the answers

What is the main function of the hook region in bacterial flagella?

<p>To connect the basal body to the filament. (A)</p> Signup and view all the answers

A researcher observes a novel bacterium moving towards a higher concentration of glucose in a culture medium. Which bacterial structure is most directly involved in this behavior?

<p>The flagella. (B)</p> Signup and view all the answers

Teichoic acids (TAs) are commonly found embedded within the peptidoglycan layers of Gram-positive bacteria. What is the primary function of teichoic acids?

<p>To increase the rigidity and stability of the peptidoglycan layer. (B)</p> Signup and view all the answers

Mycobacteriaceae bacteria possess an external layer of waxy mycolic acids in their cell wall. What property does this layer impart to these bacteria?

<p>Acid-fastness, requiring specialized stains for microscopy. (D)</p> Signup and view all the answers

Gram-negative bacteria have a more complex cell envelope compared to Gram-positive bacteria. Which structural component is unique to Gram-negative bacteria?

<p>An outer membrane containing lipopolysaccharide (LPS). (D)</p> Signup and view all the answers

Lipopolysaccharide (LPS) is a potent endotoxin found in Gram-negative bacteria. Which component of LPS is responsible for its toxic effects on the host?

<p>Lipid A, which triggers the host's immune response. (B)</p> Signup and view all the answers

Archaeal cell walls differ significantly from bacterial cell walls. What is the primary distinguishing feature of archaeal cell walls?

<p>They lack peptidoglycan and instead contain pseudopeptidoglycan or other polymers. (D)</p> Signup and view all the answers

Glycocalyces are sugar coats found on the exterior of some prokaryotic cells. How do glycocalyces contribute to the formation of biofilms?

<p>By enabling cells to adhere to surfaces and each other. (C)</p> Signup and view all the answers

A bacterial isolate from a patient's wound is found to produce a capsule. What is the most likely effect of this capsule on the bacterium's pathogenicity?

<p>The capsule will protect the bacterium from phagocytosis by immune cells. (D)</p> Signup and view all the answers

S-layers are cell envelope structures found in both bacteria and archaea. What is a proposed function of S-layers in prokaryotic cells?

<p>To help the cell withstand osmotic pressure. (D)</p> Signup and view all the answers

A patient is diagnosed with pneumonia and treated with amoxicillin, but their symptoms do not improve. What is the most likely reason for the antibiotic's failure?

<p>The causative agent lacks peptidoglycan in its cell wall. (C)</p> Signup and view all the answers

A microbiologist is studying a newly discovered bacterial species. Upon analysis, they find that the cell wall contains NAM. Which of the following conclusions can they make?

<p>The bacterium could be either Gram-positive or Gram-negative. (B)</p> Signup and view all the answers

A researcher is investigating a bacterial strain that exhibits increased resistance to phagocytosis. Which cell structure is most likely responsible for this phenomenon?

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

An experiment involves treating two different bacterial species with lysozyme, an enzyme that cleaves the beta(1,4) glycosidic bonds between NAM and NAG in peptidoglycan. Which bacterial species would be more susceptible to lysis (cell rupture)?

<p>A Gram-positive species with a thick peptidoglycan layer. (B)</p> Signup and view all the answers

In a research study analyzing different bacterial strains, it is observed that one particular strain exhibits enhanced adhesion to various surfaces, leading to increased biofilm formation. Which of the following cell structures is most likely contributing to this enhanced adhesion?

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

A hospital lab is testing the effectiveness of a new disinfectant on a bacterial sample. After applying the disinfectant, they notice that the bacterial cells remain intact, even though their metabolic activity has ceased. Which cell wall component could be providing resistance to the disinfectant?

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

Which of the following structural components is responsible for the symptoms of fever and septic shock in infections with gram-negative bacteria?

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

Flashcards

Cell

The fundamental unit of life, as stated by cell theory.

Cytoplasm

Gel-like substance inside cells, containing water and chemicals needed for growth.

Plasma membrane

A membrane enclosing the cytoplasm.

Chromosomes

Structures containing the genetic blueprints of the cell.

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Ribosomes

Organelles responsible for protein production.

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Prokaryotic cells

Cells lacking a nucleus and other complex membrane-bound organelles.

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Eukaryotic cells

Cells with a nucleus and complex membrane-bound organelles.

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Organelles

Compartments within eukaryotic cells, bounded by membranes, that perform specific functions.

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Cell Morphologies

Shapes of prokaryotic cells

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Cell Wall

Structure that maintains cell shape and protects from osmotic pressure changes.

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Osmotic Pressure

Pressure caused by solute concentration differences across a membrane.

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Isotonic Medium

Environment where solute concentrations are equal inside and outside the cell.

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Hypertonic Medium

Environment where solute concentration is greater outside the cell.

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Hypotonic Medium

Environment where solute concentration is greater inside the cell.

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Crenation

Shrinking of a cell due to water loss in a hypertonic environment.

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Plasmolysis

Contraction of the plasma membrane in cells with a cell wall in a hypertonic environment.

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Lysis

Bursting of a cell due to excessive water intake in a hypotonic environment.

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Tonicity

Ability of a cell to withstand changes in osmotic pressure.

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Nucleoid

Region in prokaryotic cells containing the DNA.

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Plasmids

Small, circular, extrachromosomal DNA molecules.

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Inclusions

Cytoplasmic structures that store excess nutrients

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Nucleoid-Associated Proteins (NAPs)

DNA-organizing proteins found in prokaryotic cells.

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Pili

Filamentous structures on bacteria aiding in attachment and biofilm formation.

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Gram-negative bacteria

Gram-negative bacteria have a cell wall structure with a thin peptidoglycan layer and an outer membrane.

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Gram-positive bacteria

Gram-positive bacteria have a cell wall structure with a thick peptidoglycan layer and no outer membrane.

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Pili biogenesis

The process by which bacteria construct and assemble pili on their surface.

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Biofilms

Structured communities of bacterial cells attached to surfaces and enclosed in a self-produced matrix.

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Volutin Granules

Inclusions that store polymerized inorganic phosphate, used in metabolism and biofilm formation.

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Sulfur Granules

Inclusions that store elemental sulfur, used for metabolism by sulfur bacteria.

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Polyhydroxybutyrate (PHB)

An inclusion surrounded by a phospholipid monolayer, used as biodegradable plastics.

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Gas Vacuoles

Accumulations of small, protein-lined vesicles of gas that allow cells to alter their buoyancy.

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Magnetosomes

Inclusions of magnetic iron oxide or iron sulfide surrounded by a lipid layer, for movement along magnetic fields.

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Carboxysomes

Inclusions containing RuBisCO and carbonic anhydrase, used for carbon metabolism.

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Endospores

Dormant structures that protect the bacterial genome under unfavorable conditions.

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Sporulation

The process by which vegetative cells transform into endospores.

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Germination

The process where endospores return to a metabolically active, vegetative state when conditions improve.

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Cell Envelope

Structures enclosing the cytoplasm and internal structures of the cell.

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Fluid Mosaic Model

Describes the fluid movement and mosaic-like composition of lipids and proteins in the plasma membrane.

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Endospore Persistence

Vegetative cells turning into endospores that allows survival for extended periods of time.

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Germinate

The process where endospores become active metabolic vegetative cells.

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Vegetative Cell

A metabolically active bacterial cell.

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Bacterial Appendages

Protein appendages on bacterial cells used for interaction.

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Fimbriae

Short, bristle-like proteins enabling cell attachment.

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Adherence in Pathogens

Attachment to host cells, essential for infection.

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F Pilus (Sex Pilus)

Pilus involved in DNA transfer between bacterial cells.

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Agglutination Assay

Classification using bacterial clumping to detect antigens.

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M Protein

Cell surface protein used to classify strep strains.

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Flagella

Structures used for movement in aqueous environments.

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Basal Body

Motor for the flagellum, embedded in the plasma membrane.

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Monotrichous Flagellum

Single flagellum at one end of a cell.

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Amphitrichous Flagella

Flagella at both ends of a cell.

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Lophotrichous Flagella

Tuft of flagella at one end of a cell.

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Peritrichous Flagella

Flagella covering the entire surface of a cell.

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Chemotaxis

Movement toward/away from chemicals.

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Bacterial 'Run'

Counterclockwise flagella rotation allowing forward movement.

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Membrane Lateral Movement

Movement of phospholipids and proteins within the plane of the membrane and between layers.

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Archaeal Membrane Features

Phospholipids formed with ether linkages and branched chains.

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Glycoproteins & Glycolipids

Proteins or phospholipids with attached sugars, aiding cell interaction with the environment.

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PLFA Analysis

Analysis used to identify unique cell types based on differences in fatty acids from phospholipids.

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Simple Diffusion

Movement down a concentration gradient, without energy input.

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Facilitated Diffusion

Diffusion across a membrane requiring carriers or channels.

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Active Transport

Transport against a concentration gradient, requiring energy (ATP).

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Group Translocation

Simultaneous transport and chemical modification during membrane transport.

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Photosynthetic Membranes

Infoldings of the plasma membrane containing photosynthetic pigments.

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Cell Wall Function

Protects the cell from harsh conditions.

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Peptidoglycan

Mesh-like structure composed of NAG and NAM; found only in bacterial cell walls.

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Lysozymes

Enzymes that break down peptidoglycan.

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Gram Staining

Differentiates bacteria based on cell wall structure.

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Internal Conditions

Internal cellular conditions stay within a certain range, despite external environmental changes.

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Small Molecules

Some molecules that can cross the membrane bilayer directly by simple diffusion.

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Gram-positive cell wall

Thick peptidoglycan layer (30-100nm) with teichoic acids.

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Teichoic acids (TAs)

Carbohydrate chains in Gram-positive cell walls that increase rigidity.

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Mycobacteriaceae cell wall

Waxy external layer of mycolic acids.

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Gram-negative cell wall

Thin peptidoglycan layer (around 4nm) and an outer membrane containing LPS.

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Periplasmic space

Space between the plasma membrane and outer membrane in Gram-negative bacteria.

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Outer membrane (Gram-negative)

Second lipid bilayer external to the peptidoglycan layer in Gram-negative cells.

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Lipopolysaccharide (LPS)

Molecule in the outer membrane of Gram-negative bacteria; acts as an endotoxin.

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Lipid A

A component of LPS; triggers fever, hemorrhaging and septic shock

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Pseudopeptidoglycan

Polymer similar to peptidoglycan found in archaeal cell walls.

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Glycocalyx

Sugar coat outside the cell wall. Capsules and slime layers are the two types.

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Capsule (cell)

Organized glycocalyx layer, made of polysaccharides or proteins.

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Slime layer

Loosely attached glycocalyx layer, easily washed off.

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S-layer

External cell envelope structure composed of structural proteins and glycoproteins.

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Amoxicillin

Enzyme that targets the peptidoglycan of bacterial cell walls.

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Study Notes

  • Cell theory establishes the cell as life's basic unit, exhibiting diversity in size, shape, structure, and function.

Fundamental Cellular Components:

  • Cytoplasm: A gel-like substance with water and chemicals for growth.
  • Plasma membrane: Encloses the cytoplasm.
  • Chromosomes: Contain cell's genetic blueprints.
  • Ribosomes: Organelles for protein production.

Prokaryotic vs. Eukaryotic Cells:

  • Prokaryotic cells lack a nucleus and have a single, circular chromosome in a nucleoid.
  • Eukaryotic cells possess a nucleus with a complex membrane and multiple, rod-shaped chromosomes.
  • Plants and animals have eukaryotic cells
  • Microorganisms can be prokaryotic (Archaea and Bacteria) or eukaryotic (Eukarya).

Cell Structures and Function:

  • Structures within cells perform specific functions, similar to organs in a body
  • Eukaryotic cells are larger than prokaryotic cells and use membrane-bound organelles to compartmentalize chemical processes.
  • Prokaryotic cells, which include bacteria and archaea, are characterized by their simpler structure. These cells do not possess specialized organelles, such as a nucleus, mitochondria, or endoplasmic reticulum, which are typically found in more complex eukaryotic cells. However, they can contain various types of inclusions, such as granules or crystals, that serve specific functions and help organize cellular processes within their cytoplasmic space. These inclusions can store nutrients, waste products, or even key metabolic enzymes, thus facilitating efficient biochemical reactions within the cell.
  • Individual prokaryotic cells of a particular species usually have a consistent shape, or cell morphology.

Cell Morphology and Arrangements:

  • Prokaryotic cell morphology, or shape, is generally maintained by the cell wall along with elements of the cytoskeleton.
  • Prokaryotic cells group in distinctive arrangements depending on the plane of cell division.

Cell Wall and Osmotic Pressure:

  • Protects cells from osmotic pressure changes
  • Osmotic pressure results from differing solute concentrations across a semipermeable membrane
  • Water moves from low to high solute concentration in osmosis
  • Isotonic medium: Equal solute concentrations inside and outside the cell, no net water movement.
  • Hypertonic medium: Higher solute concentration outside the cell, water exits causing crenation in cells without a cell wall or plasmolysis in cells with a cell wall.
  • Hypotonic medium: Higher solute concentration inside the cell, water enters, potentially causing lysis (bursting) in cells without a cell wall.
  • Tonicity: Cell's ability to withstand osmotic pressure changes.
  • Cell walls allow cells to better withstand changes in osmotic pressure.

Genetic Material:

  • All cellular life has a DNA genome organized into chromosomes
  • Prokaryotic chromosomes are circular, haploid, and located in the nucleoid region
  • Nucleoid-associated proteins (NAPs) organize and package prokaryotic chromosomes, functioning similarly to histones in eukaryotes
  • Plasmids: Extrachromosomal DNA that carries advantageous genes like antibiotic resistance.

Ribosomes:

  • All life forms synthesize proteins using ribosomes, but ribosomes differ structurally across domains.
  • Prokaryotic ribosomes (70S) are in the cytoplasm, while eukaryotic cytoplasmic ribosomes are larger (80S).
  • Bacterial and archaeal ribosomes have different proteins and rRNA molecules.

Inclusions:

  • Prokaryotic cells store excess nutrients in cytoplasmic inclusions to reduce osmotic pressure.
  • Glycogen and starches: Store carbon for energy.
  • Volutin granules (metachromatic granules): Store polymerized inorganic phosphate for metabolism and biofilm formation.
  • Sulfur granules: Store elemental sulfur for metabolism (e.g., in Thiobacillus).
  • Polyhydroxybutyrate (PHB): Stored in inclusions surrounded by a phospholipid monolayer and used for bioplastics.
  • Gas vacuoles: Protein-lined vesicles of gas that adjust buoyancy.
  • Magnetosomes: Contain magnetic iron oxide or iron sulfide that allow cells to align along magnetic fields.
  • Carboxysomes: Proto-organelles containing RuBisCO and carbonic anhydrase for carbon metabolism.

Endospores:

  • Some bacteria can form them
  • Structures protect the bacterial genome in a dormant state during unfavorable conditions.
  • Sporulation: Vegetative cells transform into endospores when nutrients are depleted.
  • Process includes septum formation, DNA forespore development, cortex formation (calcium and dipicolinic acid layers), and a protein coat
  • Endospores can remain dormant for extended periods, germinating when conditions improve
  • Bacillus and Clostridium are clinically significant endospore-forming genera.

Cell Envelope:

  • Includes all structures enclosing the cell (cell wall, plasma membrane).
  • Plasma membrane is selectively permeable
  • Is composed of a fluid mosaic of lipids and proteins.

Plasma Membrane Composition:

  • Bacterial and eukaryotic membranes: Bilayers of phospholipids with ester linkages and proteins.
  • Archaeal membranes: Ether linkages, branched chains, and can be bilayers or monolayers.
  • Glycoproteins and glycolipids: Carbohydrates attached to membrane proteins and phospholipids for cell interaction with the external environment.
  • Phospholipid-derived fatty acid analysis (PLFA): Used to identify unique cell types based on fatty acid differences.

Membrane Transport Mechanisms:

  • Simple diffusion: Molecules move from high to low concentration following the concentration gradient.
  • Facilitated diffusion: Carrier or channel proteins help molecules cross the membrane.
  • Active transport: Moves molecules against the concentration gradient, requiring energy (ATP).
  • Group translocation: Substances are chemically modified as they enter the cell, eliminating the need for transport against an unfavorable gradient (e.g., bacterial phosphotransferase system).

Photosynthetic Membranes:

  • Cyanobacteria (thylakoids) and photosynthetic bacteria (chromatophores, lamellae, or chlorosomes) have infoldings of the plasma membrane that enclose photosynthetic pigments.

Cell Wall Structure and Function:

  • Protects the cell from harsh external conditions
  • Peptidoglycan: Major component of bacterial cell walls, composed of NAG and NAM chains linked by peptide bridges
  • Antibiotics target peptidoglycan synthesis
  • Lysozyme digests peptidoglycan in bacterial cell walls.

Gram-Positive vs. Gram-Negative Cell Walls:

  • Gram-positive: Thick peptidoglycan layer (30–100 nm) with teichoic acids (TAs) for stability and rigidity
  • Gram-negative: Thin peptidoglycan layer (about 4 nm), periplasmic space, and an outer membrane containing lipopolysaccharide (LPS)

Cell Wall of Acid-Fast Bacteria

  • Mycobacteriaceae have an external layer of waxy mycolic acids in their cell wall
  • Acid-fast stains must be used to penetrate the mycolic acid layer for purposes of microscopy

Gram-Negative Outer Membrane:

  • Contains lipopolysaccharide (LPS), acting as an endotoxin
  • Lipid A, core polysaccharide, and O side chain
  • O side chain antigens are used to identify pathogenic strains (e.g., E. coli O157:H7).

Archaeal Cell Walls:

  • Lack peptidoglycan; contain pseudopeptidoglycan (pseudomurein), glycoproteins, or polysaccharides
  • Some archaea lack cell walls entirely.

Glycocalyx:

  • Sugar coat outside the cell wall (capsules and slime layers).
  • Capsule: Organized layer composed of polysaccharides or proteins.
  • Slime layer: Less organized, loosely attached layer composed of polysaccharides, glycoproteins, or glycolipids.
  • Allows cells to adhere to surfaces and form biofilms (surface-attached microbial communities that offer protection).
  • Capsules enhance pathogenicity by preventing phagocytosis (e.g., Streptococcus pneumoniae).

S-Layer:

  • Composed of structural proteins and glycoproteins outside the cell wall (bacteria) or serving as the cell wall (archaea)
  • Functions include withstanding osmotic pressure and interacting with the host immune system.

Filamentous Appendages:

  • Fimbriae and pili: Enable attachment to surfaces and to other cells, important for colonization, infectivity, and virulence.
  • F pilus (sex pilus): Transfers DNA between bacterial cells.

Cell Surface Antigens:

  • Rebecca Lancefield discovered that one group of S. pyogenes was associated with a variety of human diseases
  • Serotyping of Streptococcus species is based on cell surface antigens (e.g., M proteins in Group A strep).

Flagella: Locomotion

  • Filaments of flagellin protein subunits
  • Basal body: Motor embedded in the plasma membrane.
  • Hook region: Connects the basal body to the filament.

Flagella Arrangements:

  • Monotrichous: Single flagellum at one end.
  • Amphitrichous: Flagellum or tufts at each end.
  • Lophotrichous: Tuft at one end.
  • Peritrichous: Flagella cover the entire surface.

Movement and Chemotaxis:

  • Bacteria move in response to light (phototaxis), magnetic fields (magnetotaxis), and chemical gradients (chemotaxis).
  • Runs: Counterclockwise flagella rotation for forward movement.
  • Tumbles: Clockwise flagella rotation for reorientation.
  • Chemotaxis: Movement toward attractants or away from repellents by adjusting run and tumble lengths.

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Explore the key differences and similarities between prokaryotic and eukaryotic cells. This includes cell structures, genetic material organization, and the presence or absence of membrane-bound organelles. Questions cover cell domains and compartmentalization.

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