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Questions and Answers
What distinguishes eukaryotic cells from prokaryotic cells regarding chromosomes?
What distinguishes eukaryotic cells from prokaryotic cells regarding chromosomes?
Which of the following is a component found in bacterial cells but not in eukaryotic cells?
Which of the following is a component found in bacterial cells but not in eukaryotic cells?
What is the method of reproduction in prokaryotic cells?
What is the method of reproduction in prokaryotic cells?
What taxonomic rank is not used in the classification of bacteria?
What taxonomic rank is not used in the classification of bacteria?
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Which of the following correctly describes the ribosomes found in eukaryotic cells?
Which of the following correctly describes the ribosomes found in eukaryotic cells?
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Which of the following pairings represents the correct nomenclature of bacteria?
Which of the following pairings represents the correct nomenclature of bacteria?
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Which characteristic relates to the morphological classification of bacteria?
Which characteristic relates to the morphological classification of bacteria?
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Which of the following is not a feature of eukaryotic cells?
Which of the following is not a feature of eukaryotic cells?
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Which enzyme can easily destroy the cell walls of many Gram positive bacteria?
Which enzyme can easily destroy the cell walls of many Gram positive bacteria?
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What is a primary function of the bacterial cell wall?
What is a primary function of the bacterial cell wall?
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Which of the following statements is true about the cell wall of Gram positive bacteria?
Which of the following statements is true about the cell wall of Gram positive bacteria?
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What is the primary structural protein of flagellae in bacteria?
What is the primary structural protein of flagellae in bacteria?
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Which of the following describes the structure of Gram-negative bacterial cell walls?
Which of the following describes the structure of Gram-negative bacterial cell walls?
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What is the composition of the capsule in bacterial cells, except for Bacillus anthracis?
What is the composition of the capsule in bacterial cells, except for Bacillus anthracis?
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Which of the following is a characteristic of pili (fimbriae) in bacteria?
Which of the following is a characteristic of pili (fimbriae) in bacteria?
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Which structure is not found in bacterial cells?
Which structure is not found in bacterial cells?
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Study Notes
Introduction to Cellular Microorganisms
- Cellular microorganisms include eukaryotes and prokaryotes
- Viruses and prions are also considered microorganisms
Learning Objectives (ILOs)
- Students must differentiate between eukaryotic and prokaryotic cells.
- Students must describe bacterial cell structures and functions.
- Students must understand virulence factors in bacteria that cause disease.
Eukaryotic vs. Prokaryotic Cells
| Feature | Eukaryotic Cell | Prokaryotic Cell |
|---|---|---|
| Nuclear membrane | Present | Absent |
| Nucleus | Present | Absent |
| Chromosomes | More than one | One |
| Cytoplasmic membrane | Contains sterols | No except Mycoplasma |
| Mesosomes | Present | Present |
| Mitochondria | Present | Absent |
| Ribosomes | 80S | 70S |
| Reproduction | Sexually or asexually | Asexually by binary fission |
| Examples | Protozoa, Fungi, Human and animal cells | Bacteria, Rickettsia |
Bacterial Classification
- Classification arranges bacteria into taxonomic groups (orders, families, genera, and species).
- Species are defined by close phenotypic resemblance (determined by biochemical tests) or genetic similarity.
- Species can be divided into subspecies or types by other typing methods.
Nomenclature
- Nomenclature is the scientific naming of microorganisms using the genus and species names (e.g., Staphylococcus aureus).
Bacterial Morphology
- Morphological characteristics include size, shape, staining properties, arrangement, motility, sporulation, and capsule.
- Size is measured in microns.
Bacterial Shape and Arrangement
- Cocci are spherical and can be arranged in bunches, diplococci, chains, or tetrads.
- Bacilli are rod-shaped and can be single, diplobacilli, or square or round ended bacilli in chains.
Bacterial Structure
- Bacteria have a chromosomal DNA, ribosomes, a cytoplasmic membrane, plasmids, inclusions, a capsule, and a cell wall
- These components are seen in diagrams of bacterial cells.
Cell Membrane
- Semipermeable membrane formed of phospholipids and proteins.
- Functions include selective permeability, nutrient transport, cell wall synthesis, DNA replication, and respiration (energy).
Intracellular Structures
- Nuclear body: containing double-stranded DNA.
- Ribosomes: involved in protein synthesis (70S sedimentation rate, 30S and 50S subunits)
- Plasmids: circular extrachromosomal DNA.
- Intracytoplasmic inclusions: food reserves
Surface Structures (Capsule)
- Usually a polysaccharide layer, but in some cases a polypeptide.
- Examples include B. anthracis (polypeptide) and Streptococcus pyogenes (hyaluronic acid).
- Not stained by Gram stain but by special stains.
- Function in antiphagocytosis and antigenic identification.
Surface Structures (Glycocalyx)
- Polysaccharide layer outside the cell.
- Function: adherence to surfaces (e.g., S. mutans and dental caries).
Cell Wall
- Gram-positive bacteria have a thick peptidoglycan layer (50-60%).
- Gram-positive walls also contain teichoic and teichuronic acids and polysaccharides.
- Gram-negative bacteria have a thin peptidoglycan layer (5-10%) with an outer membrane containing lipopolysaccharide (LPS) and proteins.
Cell Wall Function
- Maintains cell shape.
- Protects against hypotonic environments
- Responsible for Gram staining
- Surface antigens
- Endotoxin activity in Gram-negative bacteria.
Bacteria with Deficient Cell Walls
- Mycoplasma, L-forms, protoplasts, and spheroplasts lack cell walls.
- These variations are influenced by environmental conditions and/or exposure to substances like penicillin.
Bacterial Enzymes
- Lysozyme is an enzyme that breaks down the peptidoglycan layer of bacterial cell walls, making the walls easily destroyed.
Flagella
- Motility organelle formed of flagellin protein.
- Composed of a filament, hook, and basal body.
- Anchored to the cell membrane.
- Different distributions include monotrichate, lophotrichate, amphitrichate, and peritrichate.
Pili (Fimbriae)
- Hair-like projections, thinner than flagella, formed of pilin protein.
- Found mainly in Gram-negative bacteria.
- Ordinary pili function in attachment.
- Sex pili facilitate DNA transfer (conjugation).
Endospores
- Highly resistant, resting forms of bacteria produced during unfavorable growth conditions.
- Found outside the host tissues.
- Made of the core material, a thick layer called cortex, and an outer coat.
- Resistant to chemicals, dryness, heat, and are killed by autoclaving.
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Description
This quiz focuses on cellular microorganisms, including the distinction between eukaryotic and prokaryotic cells. It covers key features of bacterial structures, functions, and virulence factors that contribute to disease. Test your understanding of the basics of microbiology and the classification of microorganisms.
