Questions and Answers
What are the shapes of prokaryotic cells?
What is a rod shape bacterium sometimes called?
bacillus
What is a coccobacillus?
It's a rod shaped bacterium so short that it can easily be mistaken for a coccus.
What is a Vibrio?
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What is a Spirillum?
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What is Spirochete?
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What does Pleomorphic mean?
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Cocci that occur in pairs are called?
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What is the structure surrounding a prokaryotic cell?
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What is the nucleoid of the prokaryotic cell?
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What contents make up the cell envelope?
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When water and nutrients are depleted, what structure do cells form?
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What is the natural habitat of bacteria called?
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Which of the following is NOT a filamentous appendage of prokaryotic cells?
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What structure provides buoyancy to a cell?
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Study Notes
Prokaryotic Cell Shapes
- Common bacterial shapes include spherical (coccus) and cylindrical (rod or bacillus).
- Coccobacillus refers to a very short rod-shaped bacterium resembling a coccus.
- Vibrio are short, curved rods while spirilla are curved rods capable of forming spirals.
- Spirochetes are long, helical cells with flexible cell walls and unique movement mechanisms.
- Pleomorphic bacteria exhibit variability in their shapes.
Prokaryotic Cell Groupings
- Prokaryotes primarily reproduce by binary fission, leading to characteristic arrangements based on division planes.
- Diplococci are cocci occurring in pairs, often indicative of specific bacterial identification like Neisseria gonorrhoeae.
- Cocci dividing in multiple planes can form cubical packets (ex. Genus Sarcina) or clusters (ex. Staphylococcus).
Multicellular Associations and Biofilms
- Some bacteria form multicellular associations, like myxobacteria that glide together and form aggregates to degrade organic material.
- In nutrient-depleted environments, cells may aggregate to form visible structures called fruiting bodies.
- Bacteria typically inhabit surfaces in assemblages known as biofilms.
Structure of Prokaryotic Cells
- The cytoplasmic membrane acts as a selective barrier, controlling the passage of molecules.
- The cell wall provides structural integrity, preventing cell content from escaping and aiding in motility and adhesion.
- The cell envelope consists of the capsule (if present), cell wall, and cytoplasmic membrane.
Cell Envelope Components
- Capsule: Distinct, gelatinous, helps bacteria adhere to surfaces and evade immune responses.
- Slime Layer: Irregular and diffuse, also aids in adhesion.
- Cell wall composed of peptidoglycan differs between Gram-positive (thick layer) and Gram-negative (thin layer surrounded by outer membrane with lipopolysaccharides).
Cytoplasmic Contents
- Plasma consists of water, enzymes, proteins, carbohydrates, lipids, and inorganic molecules; ribosomes and storage granules are present.
- Nucleoid is the gel-like region containing chromosomes, not membrane-bound.
Key Prokaryotic Cell Structures
- Filamentous Appendages: Proteins that form helical chains for motility.
- Flagella: Provide motion.
- Pili serve various functions; types include fimbriae (adhesion) and sex pili (DNA transfer).
- Ribosomes are critical for protein synthesis, forming 70s ribosomes from 30s and 50s subunits.
- Gas vesicles help with buoyancy.
Genetic Material
- DNA contains genetic information, typically as a single circular strand.
- Plasmids are extra-chromosomal DNA contributing to genetic variation.
- Endospores are dormant cells resistant to unfavorable conditions.
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Description
This quiz consists of flashcards covering the key concepts of prokaryotic cell shapes in Microbiology Chapter 3.3. Learn about the different forms of bacteria, such as cocci and bacilli, and their characteristics. These flashcards will enhance your understanding of bacterial morphology.
