Questions and Answers
What is a defining feature of prokaryotic cells compared to eukaryotic cells?
Which of the following components is NOT found in prokaryotic cells?
What type of DNA structure is found in prokaryotic cells?
Which method of reproduction is primarily used by prokaryotes?
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How do photosynthetic prokaryotes like cyanobacteria contribute to their environment?
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What is the primary structural component of the cell wall in bacterial cells?
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Which of the following adaptations do bacteria exhibit to survive unfavorable conditions?
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How do the cell walls of archaea differ from those of bacteria?
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What type of chromosome do both bacteria and archaea typically possess?
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In which type of environments are archaebacteria typically found?
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Study Notes
Definition of Prokaryotic Cells
- Prokaryotic cells are single-celled microorganisms and among the earliest life forms on Earth.
- They include two domains: Bacteria and Archaea.
- Photosynthetic prokaryotes, such as cyanobacteria, are capable of performing photosynthesis.
- Composed of a single membrane, all cellular reactions occur within the cytoplasm.
- Can be free-living organisms or exist as parasites.
Characteristics of Prokaryotic Cells
- Lack a nuclear membrane; instead, the genetic material is located in the nucleoid region of the cytoplasm.
- Can exhibit various shapes: spherical (cocci), rod-shaped (bacilli), or spiral (spirilla).
- Do not contain organelles typical of eukaryotic cells, such as mitochondria, endoplasmic reticulum, or Golgi bodies.
Structure of Prokaryotic Cells
- Plasma Membrane: A protective phospholipid layer that separates the interior of the cell from the external environment.
- Cytoplasm: A jelly-like substance where cellular components are suspended.
- DNA: Circular DNA serves as genetic material, directing protein synthesis and regulating cell activities.
- Ribosomes: Site of protein synthesis; some prokaryotes may also have cilia and flagella for movement.
Reproduction in Prokaryotes
- Prokaryotes primarily reproduce through binary fission, a simple division process.
- Recombination occurs via gene transfer between bacteria through:
- Conjugation: Direct transfer of DNA between two bacteria.
- Transformation: Uptake of free DNA from the environment.
- Transduction: Transfer of DNA between bacteria via viruses.
Examples of Prokaryotic Cells
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Bacterial Cells:
- Found in diverse environments, from soil to the human body; they exhibit varied shapes and structures.
- Cell wall composed of peptidoglycan which provides structural integrity.
- Unique structures include pili for attachment, flagella for motility, and capsules for protection.
- Can carry plasmids, which are small, circular pieces of DNA.
- Capable of forming endospores to survive harsh environmental conditions.
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Archaeal Cells:
- Unicellular and similar in shape/size to bacteria, but often found in extreme environments like hot springs.
- Cell walls lack peptidoglycan and have distinct lipid membranes with unique stereochemistry.
- Possess a circular chromosome and plasmids, similar to bacteria, but have differences in biochemistry.
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Description
This quiz covers the definition, characteristics, and structure of prokaryotic cells, which include Bacteria and Archaea. Learn about their unique features, such as the lack of a nuclear membrane and various cell shapes. Test your understanding of these fundamental microorganisms that play essential roles in our ecosystem.
