Questions and Answers
How are Archaea like Eukarya?
Genes encoding protein (replication, transcription, translation)
How are Archaea like Bacteria?
Genes for metabolism
What elements are unique to Archaea?
Unique rRNA gene structure, capable of methanogenesis
Where are Archaea normally found?
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What kind of shapes do Archaea show?
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What is different about the cell membrane of Archaea?
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Do Archaeal cell walls have peptidoglycan?
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Do Archaeal cells always have cell walls? What do they use instead?
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Do Archaeal cells have slime layers and capsules?
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How are the lipids in Archaea unique?
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What is pseudomurein?
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Do Archaea have inclusions?
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What size are the ribosomes in Archaea?
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What group are Archaeal ribosomes more similar to, Bacteria or Eukarya?
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What shape is Archaeal DNA?
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How is Archaeal DNA compacted?
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What is different about the nucleoid compared to Bacteria?
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What two external structures are unique to Archaea?
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What are cannulae?
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What are Hami?
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How are bacterial cell envelopes and archaeal cell envelopes different?
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How are the ribosomes in Archaeal cells and Bacterial cells different?
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How is the nucleoid different in Archaea compared to Bacteria?
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Study Notes
Characteristics of Archaea
- Archaea share genetic similarities with eukarya, especially in genes responsible for protein synthesis (replication, transcription, translation).
- Similar to bacteria, Archaea possess genes essential for metabolic processes.
Unique Features of Archaea
- Possess a distinctive rRNA gene structure not found in other domains.
- Capable of methanogenesis, a process of generating methane.
Habitat and Environment
- Typically thrive in extreme conditions: hypersaline environments, high acidity or alkalinity, and elevated temperatures.
Morphology
- Exhibit various shapes similar to bacteria, with unique forms such as branched and flat structures; not observed as spirochetes.
Cell Structures
- Archaea have unique cell membranes composed of monolipid structures, differing significantly from typical bacterial lipid compositions.
- Lack peptidoglycan in their cell walls, using an S-layer instead for structural integrity.
- Inclusions are present within archael cells.
Cell Wall Composition
- Most archaea do not possess cell walls; when present, they are primarily composed of S-layer proteins.
- Rarely exhibit slime layers or capsules, distinguishing them from many bacteria.
Lipid Characteristics
- The lipids in archaea feature hydrocarbon tails derived from isoprene units with ether linkages, setting them apart from other organisms.
DNA Organization
- Archaea possess circular DNA, similar to bacteria, but their nucleoid is irregularly shaped and not membrane-bound.
- DNA is compacted with histones and supercoiling, offering a sophisticated level of organization.
Ribosomes and Genetic Relationships
- Archaea and bacteria possess ribosomes of similar size, but archaeal ribosomes are more closely related to those of eukarya based on nucleotide sequences.
External Structures
- Unique external structures include cannulae, hollow tubelike projections from thermophilic archaea whose function remains unclear.
- Hami resemble hooks and may facilitate adherence to surfaces.
Differences from Bacterial Structures
- Archaea's cell envelopes contain isoprenol hydrocarbons and may form monolayers, in contrast to the bilayer structure of bacterial cell membranes.
- Absence of peptidoglycan in archaea cell walls, with alternative S-layers often providing structural support.
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Description
Explore the fascinating world of Archaea, unique microorganisms that share some similarities with both bacteria and eukarya. This quiz covers their genetic traits, metabolic processes, and distinctive features such as their unique cell structure and extreme environmental habitats. Test your knowledge on their morphology and cell structures as well.