Bacterial Structure and Morphology Quiz
48 Questions
5 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to Lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What are the three basic shapes into which bacteria are classified?

  • Cocci, bacilli, and spirilla
  • Cocci, bacilli, and flagella
  • Cocci, bacilli, and spirochetes (correct)
  • Cocci, pleomorphic, and spirochetes

Which structure provides rigid support to bacterial cells?

  • Flagella
  • Cell membrane
  • Cytoplasm
  • Peptidoglycan (correct)

What is a characteristic feature of gram-positive bacteria in terms of their cell wall structure?

  • No peptidoglycan layer at all
  • Thin peptidoglycan layer and an outer membrane
  • Thick peptidoglycan layer and no outer membrane (correct)
  • Thin layer of glycocalyx and an outer membrane

Which of the following is NOT a typical morphology of cocci?

<p>Cocci with square ends (A)</p> Signup and view all the answers

What are pleomorphic bacteria known for?

<p>Being variable in shape (A)</p> Signup and view all the answers

Which component is the outermost part of a bacterial cell, excluding Mycoplasma?

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

What connects glycan chains in the peptidoglycan structure?

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

Which of the following is a specialized structure outside the bacterial cell wall?

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

What is the primary function of penicillin binding proteins (PBP) in bacteria?

<p>Catalyze the formation of peptide bonds in peptidoglycan (C)</p> Signup and view all the answers

Which of the following statements about the action of beta-lactam antibiotics is true?

<p>They inhibit peptidoglycan synthesis by binding with transpeptidases. (A)</p> Signup and view all the answers

Teichoic acids are primarily associated with which type of bacteria?

<p>Gram-positive bacteria (A)</p> Signup and view all the answers

What is the role of lipopolysaccharide (LPS) in gram-negative bacteria?

<p>It serves as a structural component of the cell membrane. (B)</p> Signup and view all the answers

What effect does teichoic acid have when induced by certain gram-positive bacteria?

<p>It activates pathways leading to septic shock. (B)</p> Signup and view all the answers

Why is LPS called an endotoxin?

<p>Because it forms a part of the membrane structure. (C)</p> Signup and view all the answers

Which statement best describes the structure of gram-negative bacteria's outer membrane?

<p>It contains a bilayered membrane with unique components. (A)</p> Signup and view all the answers

What is the effect of transpeptidase inhibition by beta-lactam antibiotics on bacterial cells?

<p>Inhibition of cell wall synthesis leading to cell lysis. (D)</p> Signup and view all the answers

What component of LPS is responsible for its toxic effects?

<p>Phospholipid called lipid A (A)</p> Signup and view all the answers

Which feature allows Mycobacteria to resist Gram staining?

<p>High concentration of mycolic acids (B)</p> Signup and view all the answers

What is the role of porin proteins in the outer membrane of gram-negative bacteria?

<p>Act as receptors for phages (C)</p> Signup and view all the answers

Which of the following correctly describes cell wall-deficient (CWD) bacteria?

<p>Lack cell wall structures (A)</p> Signup and view all the answers

Which function is NOT typically associated with the cytoplasmic membrane of prokaryotic cells?

<p>Synthesis of sterols (A)</p> Signup and view all the answers

What is the clinical significance of the outer polysaccharide in LPS?

<p>It acts as an O antigen for organism identification. (A)</p> Signup and view all the answers

How do bacteria survive when exposed to lysozyme or antibiotics targeting the cell wall?

<p>By losing cell wall structures (B)</p> Signup and view all the answers

What is one of the functions of the cytoplasmic membrane in bacteria?

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

Which component of the bacterial capsule is primarily responsible for its serologic type variation?

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

How does the capsule of a bacterium contribute to its virulence?

<p>By limiting phagocytic engulfment (A)</p> Signup and view all the answers

What is the quellung reaction associated with?

<p>The swelling of the capsule in the presence of homologous antibody (A)</p> Signup and view all the answers

What role do capsular polysaccharides play in vaccines?

<p>They serve as antigens (B)</p> Signup and view all the answers

What type of motion do spirochetes use to move?

<p>Undulating motion produced by an axial filament (A)</p> Signup and view all the answers

Which of the following best describes the arrangement of flagella on some bacteria?

<p>Distributed evenly over the entire surface (D)</p> Signup and view all the answers

Which of the following statements about flagella is true?

<p>Flagella assist in chemotaxis. (C)</p> Signup and view all the answers

What is a common infection associated with flagellated motile bacteria?

<p>Urinary tract infections (C)</p> Signup and view all the answers

What role do pili play in bacterial function?

<p>Mediating attachment to human cell receptors (B)</p> Signup and view all the answers

What is the specialized type of pilus that facilitates bacterial conjugation?

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

Which structure allows bacteria to adhere firmly to surfaces and is involved in dental plaque formation?

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

Which bacterial genera are known for forming highly resistant spores in response to adverse conditions?

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

What key component is contained within a bacterial spore?

<p>Keratin-like coat (A)</p> Signup and view all the answers

What happens during the process of sporulation in bacteria?

<p>Spores are formed due to nutrient depletion (C)</p> Signup and view all the answers

Which of the following bacteria is nonpathogenic due to the absence of pili?

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

What is the function of the mesosome during cell division?

<p>It originates the transverse septum that divides the cell. (C)</p> Signup and view all the answers

Which of the following statements is true regarding pili?

<p>Pili help in bacterial adhesion. (C)</p> Signup and view all the answers

Which component is NOT part of the cytoplasm's structure in prokaryotes?

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

How do bacterial ribosomes differ from eukaryotic ribosomes?

<p>They have different subunit compositions. (D)</p> Signup and view all the answers

What distinguishes bacterial DNA from eukaryotic DNA?

<p>Bacterial DNA is a single, circular molecule without introns. (A)</p> Signup and view all the answers

What role do plasmids have in bacteria?

<p>They replicate independently of the bacterial chromosome. (C)</p> Signup and view all the answers

Which characteristic of ribosomes is crucial for the selective action of antibiotics?

<p>Differences in ribosomal RNA and protein composition. (A)</p> Signup and view all the answers

Which of the following statements about the nucleoid is true?

<p>It is where the bacterial DNA is located. (A)</p> Signup and view all the answers

What type of granules are found in the cytoplasm of bacteria?

<p>Granules that serve as storage areas for nutrients. (B)</p> Signup and view all the answers

Flashcards

Bacterial Morphology

The study of bacterial shapes and forms, classified into cocci (spherical), bacilli (rod-shaped), and spirochetes (spiral-shaped).

Peptidoglycan

A polymer found only in bacterial cell walls, providing structural support and maintaining cell shape.

Bacterial Cell Wall

The outermost layer of most bacteria (except Mycoplasma), composed of peptidoglycan and sometimes an outer membrane; provides rigidity and shape.

Cocci Bacteria

Spherical-shaped bacteria.

Signup and view all the flashcards

Bacilli Bacteria

Rod-shaped bacteria.

Signup and view all the flashcards

Spirochetes Bacteria

Spiral-shaped bacteria.

Signup and view all the flashcards

Pleomorphic Bacteria

Bacteria that can vary in shape.

Signup and view all the flashcards

Gram Positive Bacteria

Have a thick peptidoglycan layer in their cell wall, which retains crystal violet dye during a Gram stain.

Signup and view all the flashcards

Transpeptidation

The process of forming peptide cross-links in peptidoglycan, a key component of bacterial cell walls.

Signup and view all the flashcards

Penicillin Binding Proteins (PBPs)

Bacterial enzymes that are crucial for forming the peptidoglycan cell wall, and are targeted by penicillin antibiotics.

Signup and view all the flashcards

Beta-lactam Antibiotics

Antibiotics that target and inactivate bacterial transpeptidases (PBPs), ultimately inhibiting peptidoglycan synthesis and bacterial cell wall formation.

Signup and view all the flashcards

Gram-negative cell wall

Bacterial cell wall with an outer membrane containing lipopolysaccharide (LPS).

Signup and view all the flashcards

Lipopolysaccharide (LPS)

Component of the outer membrane of gram-negative bacteria cell wall, also known as endotoxin.

Signup and view all the flashcards

Teichoic Acids

Components of the bacterial cell wall in gram-positive bacteria.

Signup and view all the flashcards

Peptidoglycan synthesis

The process where bacterial cell walls are built.

Signup and view all the flashcards

Endotoxin

Lipopolysaccharide (LPS). Toxin component of gram-negative bacteria.

Signup and view all the flashcards

Capsule

A protective layer surrounding some bacteria, composed of polysaccharides. It helps bacteria evade immune cells, causes specific serological variations in the bacterium and contributes to virulence.

Signup and view all the flashcards

Quellung Reaction

A laboratory test used to identify bacteria based on the swelling of their capsule in the presence of specific antibodies.

Signup and view all the flashcards

Flagella

Long, whip-like appendages that allow bacteria to move towards nutrients and other attractants.

Signup and view all the flashcards

Chemotaxis

The movement of bacteria toward or away from chemical stimuli.

Signup and view all the flashcards

Axial Filament

A flagellum-like structure found in spirochetes, wrapping around the spiral cell to cause an undulating movement.

Signup and view all the flashcards

H Antigens

Flagella antigens used in laboratory identification of certain bacteria.

Signup and view all the flashcards

Flagella in Pathogenesis

Flagella can contribute to infections by enabling bacteria to propel themselves into specific tissues.

Signup and view all the flashcards

Capsular Polysaccharide Vaccines

Vaccines using purified capsular polysaccharides from bacteria to provide immunity against specific infections.

Signup and view all the flashcards

What is LPS?

Lipopolysaccharide (LPS) is a complex molecule found in the outer membrane of Gram-negative bacteria. It's composed of three main parts: lipid A, core polysaccharide, and outer polysaccharide.

Signup and view all the flashcards

What does Lipid A do?

Lipid A is the toxic component of LPS. It triggers an immune response in the body that can lead to septic shock, a life-threatening condition.

Signup and view all the flashcards

What is O antigen?

O antigen is the outermost part of LPS, made up of repeating sugar units. It's unique to each bacterial species, helping scientists identify different bacteria.

Signup and view all the flashcards

What are porins?

Porins are protein channels in the outer membrane of Gram-negative bacteria. They allow small molecules to pass through the membrane into the cell.

Signup and view all the flashcards

What are Mycolic acids?

Mycolic acids are long-chain fatty acids found in the cell walls of Mycobacteria, like the bacteria that cause tuberculosis.

Signup and view all the flashcards

Why are Mycobacteria acid-fast?

Mycobacteria are called 'acid-fast' because their cell walls, rich in mycolic acids, resist decolorization with acid-alcohol after staining.

Signup and view all the flashcards

What are L-form bacteria?

L-form bacteria are bacteria that lack a cell wall. They can survive by losing the cell wall structure under pressure from lysozymes or antibiotics.

Signup and view all the flashcards

What are the four functions of the cytoplasmic membrane?

The cytoplasmic membrane in prokaryotes has four key functions: 1. Active transport: moving molecules into the cell, 2. Energy generation: producing energy, 3. Cell wall synthesis: building the cell wall, 4. Secretion: releasing enzymes and toxins.

Signup and view all the flashcards

Mesosome

An invagination of the cytoplasmic membrane in bacteria that plays a crucial role in cell division and DNA attachment.

Signup and view all the flashcards

Cytoplasm

The gel-like substance within a bacterial cell, containing ribosomes, nutrients, and the nucleoid region where DNA is located.

Signup and view all the flashcards

Ribosomes

Tiny structures inside bacteria responsible for protein synthesis, different in size and composition from eukaryotic ribosomes.

Signup and view all the flashcards

Nucleoid

The region within the cytoplasm of bacteria where the single, circular DNA molecule is located, lacking a nuclear membrane, nucleolus, or histones.

Signup and view all the flashcards

Plasmids

Extrachromosomal, circular DNA molecules in bacteria that replicate independently of the bacterial chromosome and can carry genes for antibiotic resistance or other traits.

Signup and view all the flashcards

What is the difference between bacterial DNA and eukaryotic DNA?

Bacterial DNA is a single, circular molecule without introns, while eukaryotic DNA is linear, has multiple chromosomes, and contains introns.

Signup and view all the flashcards

Granules

Storage areas within the cytoplasm of bacteria that hold nutrients and stain differently with specific dyes.

Signup and view all the flashcards

What are pili?

Pili are hair-like structures on the surface of bacteria, shorter and straighter than flagella, primarily found on gram-negative bacteria.

Signup and view all the flashcards

Pili's role in attachment

Pili help bacteria attach to specific receptors on human cells, enabling them to colonize and potentially cause infections.

Signup and view all the flashcards

Sex Pilus

A specialized pilus that facilitates the transfer of genetic material between bacteria during conjugation.

Signup and view all the flashcards

Glycocalyx

A protective layer secreted by some bacteria, composed of sugars, acting like a sticky coating that allows bacteria to adhere to surfaces.

Signup and view all the flashcards

Glycocalyx and dental plaque

The glycocalyx helps bacteria like Streptococcus mutans bind to teeth, contributing to plaque formation, which can lead to dental caries.

Signup and view all the flashcards

What are endospores?

Endospores are highly resistant structures formed by certain bacteria, like Bacillus and Clostridium, in response to harsh conditions.

Signup and view all the flashcards

Conditions for spore formation

Spore formation occurs when bacteria face unfavorable conditions, such as lack of nutrients like carbon and nitrogen.

Signup and view all the flashcards

Endospore composition

Endospores contain bacterial DNA, cytoplasm, cell membrane, peptidoglycan, very little water, and a thick, protective coat.

Signup and view all the flashcards

Study Notes

Bacterial Structure

  • Bacteria are classified into three basic groups: cocci (round), bacilli (rods), and spirochetes (spiral).
  • Some bacteria have variable shapes, called pleomorphic.
  • Bacteria's morphology is characterized by different arrangements: cocci in clusters (Staphylococcus), chains (Streptococcus), pairs, or other shapes.
  • Rods (bacilli) can appear in various forms.
  • Spirochetes can have loose or tight coils (coils).

Learning Objectives

  • Students should define typical bacteria.
  • Students should know bacterial morphology—appearance (cocci, bacilli, spirochetes).
  • Students should understand cell wall structure (peptidoglycans).
  • Gram-positive and gram-negative bacteria cell wall structures should be understood (differences in thickness and composition).
  • Components of the cell wall (cell membrane, mesosomes, ribosomes, genetic material) should be familiar.
  • Specialized structures outside the cell wall (capsule, pili, flagella, glycocalyx) should be known.

Structure of Bacterial Cells

  • The cell wall is the outermost layer of bacteria (except Mycoplasma).
  • Some bacteria have surface features external to their cell wall, such as a capsule, flagella and pili.
  • Peptidoglycan is the key structural component, providing support and maintaining shape.
  • Its thickness differs between gram-positive and gram-negative bacteria.

Cell Wall

  • Gram-positive cell walls are thick, with 50% of dry weight as peptidoglycan.
  • Gram-negative cell walls are thin, with 5-10% of dry weight as peptidoglycan.
  • Peptidoglycan in bacterial walls is also known as murein or mucopeptide.
  • It provides the cell with rigid support and maintains its shape.
  • The structure of peptidoglycan includes glycan chains connected through peptide bonds.
  • These bonds are the target for enzymes like lysozyme.

Cytoplasmic Membrane

  • The cytoplasmic membrane lies just inside the cell wall.
  • It's similar to eukaryotic membranes – a phospholipid bilayer.
  • It has essential functions for the cell (active transport of molecules, energy generation, protein synthesis, enzyme secretion).

Mesosome

  • Structures formed by invaginations of the cytoplasmic membrane.
  • Involved in cell division.

Cytoplasm

  • Two distinct regions (amorphous matrix and nucleoid region) are distinguishable in the cytoplasm.
  • The amorphous matrix contains ribosomes, nutrients, metabolites, and plasmids.
  • The nucleoid region contains DNA.

Ribosomes

  • Ribosomes are the sites of protein synthesis.
  • Bacterial ribosomes are 70S (composed of 50S and 30S subunits).

Important Note

  • Differences in the ribosome structure have relevance for antibiotics.

Granules

  • The cytoplasm may contain storage granules for nutrients.

Nucleoid

  • Region of the cytoplasm that holds bacterial DNA.
  • Bacterial DNA is a single, circular molecule.
  • Unlike eukaryotic DNA, this DNA has no nucleus, nucleolus, mitotic spindle, or histones.

Plasmids

  • Extrachromosomal DNA molecules that can replicate independently.
  • May be integrated into the bacterial chromosome.
  • Often carry genes for antibiotic resistance, resistance to heavy metals, toxins, and other functions.
  • Two Types: Transmissible and Non-transmissible.

Transposons

  • Segments of DNA capable of moving within or between DNA molecules (e.g., bacterial chromosomes, plasmids, or phages).
  • Do NOT replicate independently.

Specialized Structures (Outside the Cell Wall)

  • Capsule: a gelatinous layer (polysaccharide, except in certain species)
  • Flagella: long, whip-like appendages used in movement (chemotaxis)
  • Pili (fimbriae): hair-like structures used in attachment and conjugation
  • Glycocalyx(slime layer): polysaccharide coating that helps attachment to surfaces.

Capsule

  • The capsule is a gelatinous layer.
  • It's made of polysaccharide except for anthrax bacillus.
  • It's composed of proteins like D-glutamic acid.
  • Capsular polysaccharides are used in vaccines.
  • Capsular structure is important for identifying bacteria and their virulence.

Flagella

  • Whip-like appendages for bacterial motility (chemotaxis).
  • Different arrangements (e.g., monotrichous, lophotrichous, amphitrichous, peritrichous) based on location on cell
  • Flagella play a crucial role in pathogenesis and disease in humans.

Pili (Fimbriae)

  • Hair-like appendages for bacterial attachment.
  • Play an important role in causing human infections (e.g., N. gonorrhoeae).
  • Different types, some for conjugation.

Glycocalyx (Slime Layer)

  • Polysaccharide coating that adheres to surfaces; allows for forming plaque (e.g., S. mutans).
  • Involved in the formation of plaque, a critical stage in dental caries.

Spores

  • Highly resistant structures in some bacteria (e.g., Bacillus, Clostridium) to survive harsh conditions
  • Spores are formed inside the bacteria cells
  • Contains bacterial DNA, cell membrane, and keratin-like material

Endospores

  • Dormant, extremely resistant forms of some bacterial species.
  • Resistant to heat, dehydration, radiation, and chemicals.

Acid-Fast Cell Walls

  • Unique to mycobacteria (e.g., M. tuberculosis)
  • Have a high lipid content (mycolic acids), with a thick layer of peptidoglycan, contributing to the acid-fast property.

Cell Wall-Deficient bacteria

  • Strains have no cell walls.
  • Exhibit decreased virulence when exposed to lysozyme or antibiotics.

Porin Proteins

  • Protein structures that create channels across the outer membrane, facilitating the passage of molecules.
  • Important role for transport of substances.
  • Serve as receptors for certain phages.

Teichoic Acid

  • Present in gram-positive bacterial cell walls.
  • These polymers either contain glycerol or ribitol-phosphate (and contain phosphate).
  • The acidic nature of the cell wall plays a role in virulence.

Lipopolysaccharide (LPS)

  • Main component of the outer membrane of gram-negative bacterial walls.
  • Responsible for toxic effects.
  • Important in identification.

### Bacterial Cytoplasmic Membrane

  • Just inside the peptidoglycan layer.
  • Similar to eukaryotic membranes (phospholipid bilayer).
  • Contains hopanoids, which act like sterols.
  • Essential for maintaining cell integrity of eukaryotic and prokaryotic cells.
  • Contains important protein complexes involved in metabolism
  • Regulates the passage of materials into and out of the cell.

Pili

  • Structures extending from the cell surface used for attachment.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Quiz Team

Related Documents

Bacterial Structure PDF

Description

Test your understanding of bacterial structure and classification in this quiz. Learn about the different types of bacteria, their shapes, and cell wall structures, including the distinctions between gram-positive and gram-negative bacteria. This quiz will cover the key components and specialized structures of bacteria as well.

More Like This

Use Quizgecko on...
Browser
Open
Browser
Browser