Questions and Answers
What component is primarily responsible for cell division in cyanobacteria?
Which method of asexual reproduction involves the transformation of vegetative cells in cyanobacteria?
In which type of cells does anaerobic nitrogen fixation primarily occur in cyanobacteria?
What is one of the primary roles of photosynthetic pigments found in cyanobacteria?
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What type of environments do cyanobacteria, such as Nostoc and Anabaena, thrive in for soil reclamation?
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What is a defining characteristic of cyanobacterial cell structure?
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What are two parts into which the protoplasm of cyanobacterial cells is divided?
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Which pigment is NOT present in the thylakoids of cyanobacteria?
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Which structure in the cyanobacterial cell helps regulate buoyancy?
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Which of the following statements about the lamellasome in cyanobacterial cells is true?
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Study Notes
Cyanobacteria: Cell Structure, Metabolism, and Reproduction
- Cyanobacteria possess a prokaryotic cell structure with a 4-layered cell wall covered by a mucilaginous sheath.
- Lack a well-defined nucleus; chromatin material is centrally located.
- Protoplasm is divided into centroplasm (colorless) and chromoplasm (pigmented).
- Heterocysts are specialized cells for anaerobic nitrogen fixation, impermeable to oxygen.
- Photosynthesis occurs mainly in vegetative cells with photosynthetic pigments such as chlorophyll a, phycocyanin (blue), phycoerythrin (red), and allophycocyanin (light blue), located in thylakoids.
- Reproduce asexually through methods like binary fission, fragmentation, or transformation into akinetes under special conditions.
- Important for environmental reclamation, serving as food for aquatic animals, and cultivation of Spirulina for protein-rich diets.
Metabolism
- Cyanobacteria are autotrophic, conducting both nitrogen fixation and photosynthesis.
- Nitrogen fixation occurs in heterocysts, which lack PS II activities and serve to fix atmospheric nitrogen.
- Photosynthesis is oxygen-evolving but occurs primarily in vegetative cells, allowing heterocysts to focus solely on nitrogen fixation.
Importance of Cyanobacteria
- They improve soil fertility through nitrogen fixation, particularly in damp and aquatic environments.
- Some species are contributors to algal blooms, which can produce toxins harmful to aquatic life and humans.
- Spirulina is a commercially significant cyanobacterium known for its rapid growth and edible, high-protein content.
Mycoplasma
- Mycoplasma are unicellular, prokaryotic organisms, notable for lacking a cell wall, making them resistant to certain antibiotics like penicillin.
- They are highly pleomorphic and reproduces by forming elementary bodies.
- The smallest known prokaryotes, like Mycoplasma gallisepticum, measure 0.3 to 0.5 µm and can cause diseases in plants and animals.
- They form characteristic 'fried egg' colonies when cultured and have linear double-stranded DNA.
General Characteristics of Prokaryotes
- Mostly unicellular; some form colonies.
- Primarily aquatic; possess structures for locomotion like flagella or cilia.
- Nutrition modes can be autotrophic, heterotrophic, or mixotrophic.
- Predominantly reproduce asexually and have a simple life cycle.
Kingdom Protista
- Protista serves as a crucial link between Monera and more complex kingdoms like Plantae, Fungi, and Animalia.
- Consists of unicellular eukaryotes, which include autotrophs like dinoflagellates and diatoms, as well as consumer-decomposer organisms and protozoans.
- Features the evolutionary ancestors of all multicellular eukaryotes.
Structure of Mycoplasma
- Composed of a lipoprotein membrane with three layers.
- Contains essential cellular components like metabolites, ribosomes, and soluble proteins.
- Non-motile and faculative anaerobes, demonstrating a simple structure but complex metabolic capabilities.
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Description
Explore the fascinating world of cyanobacteria through this quiz, which delves into their unique cell structure, metabolism, and reproduction. Understand the role of protoplasm, the significance of sterols, and the mechanisms involved in cell division.
