Chapter 27 Prokaryotes Flashcards
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What are prokaryotes?
Prokaryotes are unicellular organisms that lack a nucleus and include bacteria and archaea.
When did prokaryotes first appear on Earth?
Prokaryotes first appeared approximately 3.5 billion years ago.
What is the size range of prokaryotic cells?
Prokaryotic cells typically range from 0.5 to 5 µm in diameter.
What is the function of the prokaryotic cell wall?
The cell wall maintains cell shape, protects the cell, and prevents it from bursting in hypotonic environments.
What is the composition of bacterial cell walls?
acterial cell walls are made of peptidoglycan, a sugar-polypeptide polymer.
How do archaeal cell walls differ from bacterial cell walls?
Archaeal cell walls lack peptidoglycan and are composed of polysaccharides and proteins.
What is the Gram staining technique used for?
Gram staining is used to categorize bacteria based on cell wall composition.
What are the characteristics of Gram-positive bacteria?
Gram-positive bacteria have a thick peptidoglycan layer and stain purple.
What are the characteristics of Gram-negative bacteria?
Gram-negative bacteria have a thin peptidoglycan layer with an outer membrane made of lipopolysaccharides and stain pink/red.
What are capsules and slime layers in prokaryotes?
Capsules are dense and well-defined outer layers, while slime layers are looser and less organized. Both enable adhesion and provide protection.
What are endospores?
Endospores are resistant, dormant structures formed by some bacteria to survive extreme conditions.
What are fimbriae and pili?
Fimbriae are hairlike appendages for attachment, while pili are longer appendages involved in DNA transfer.
What is the structure of bacterial flagella?
Bacterial flagella consist of a motor, hook, and filament, and are composed of 42 different proteins.
What is taxis in prokaryotes?
Taxis is the directed movement of prokaryotes in response to stimuli, such as chemotaxis towards nutrients or away from toxins.
How do prokaryotic genomes differ from eukaryotic genomes?
Prokaryotic genomes are typically single circular chromosomes located in the nucleoid, with additional DNA in plasmids.
What is binary fission?
Binary fission is the process by which prokaryotes reproduce, leading to exponential population growth under ideal conditions.
What are the three mechanisms of genetic recombination in prokaryotes?
The three mechanisms are transformation, transduction, and conjugation.
What is transformation in prokaryotes?
Transformation is the uptake of foreign DNA from the surroundings by a prokaryotic cell.
What is transduction in prokaryotes?
Transduction is the transfer of DNA from one bacterial cell to another by bacteriophages.
What is conjugation in prokaryotes?
Conjugation is the transfer of DNA between two bacterial cells that are temporarily connected.
What is the F factor in prokaryotes?
The F factor (fertility factor) is a DNA segment that allows the formation of pili and DNA transfer during conjugation.
What are R plasmids?
R plasmids are plasmids that carry antibiotic resistance genes.
What are the oxygen requirements for prokaryotic metabolism?
Prokaryotes can be obligate aerobes, obligate anaerobes, or facultative anaerobes.
What is nitrogen fixation?
Nitrogen fixation is the conversion of atmospheric nitrogen (N₂) into ammonia (NH₃) by certain prokaryotes.
What is metabolic cooperation in prokaryotes?
Metabolic cooperation involves prokaryotic cells working together to utilize environmental resources, such as in biofilms or filamentous cyanobacteria.
What are biofilms?
Biofilms are surface-coating colonies of prokaryotic cells that produce polysaccharides and proteins to stick together and to surfaces.
What is the significance of prokaryotic diversity and evolution?
Prokaryotes have diversified extensively over billions of years, adapting to nearly all life-sustaining environments and playing crucial roles in ecosystems.
What are extremophiles?
Extremophiles are archaea that thrive in extreme conditions, such as high salinity or high temperatures.
What are methanogens?
Methanogens are archaea that produce methane as a by-product of energy production and are strict anaerobes.
What is the ecological importance of prokaryotes?
Prokaryotes are essential for nutrient cycling, decomposition, and maintaining ecosystem health.
