Questions and Answers
Which structure is primarily involved in cell division in bacteria?
What is the primary function of the capsule in bacteria?
Which antibiotic class targets the nucleoid structure in bacteria?
What is the composition of pili or fimbriae?
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Which structure is categorized as non-essential in bacteria?
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What is a primary distinguishing characteristic of prokaryotic cells?
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Which group of microorganisms is classified as acellular and inert outside of living cells?
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Bacteria belong to which kingdom?
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What structure is found in prokaryotic cells that contains DNA?
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Which of the following statements about eukaryotic organisms is correct?
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Which of the following groups is NOT considered a major agent of human infectious disease?
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What is a key function of the nuclear membrane in eukaryotic cells?
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Which statement accurately describes the chromosomes in eukaryotic cells?
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Which characteristic is associated exclusively with eukaryotic cells?
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What is the primary function of the bacterial cell wall containing peptidoglycan?
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What type of nucleic acid do viruses contain?
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Which feature distinguishes prokaryotic cells from eukaryotic cells in terms of DNA organization?
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What structure encases the nucleic acid in viruses?
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What type of ribosomes do eukaryotic cells possess?
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What is the primary reason viruses are classified as obligate intracellular parasites?
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Which statement about the cell membrane of bacteria is true?
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What is the approximate diameter range of viruses?
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How can bacteria be categorized based on shape?
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What is the chromosome number comparison between prokaryotic and eukaryotic cells?
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What is true about the nucleic acid of bacteria?
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Which of the following statements about Gram staining is accurate?
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How do enveloped viruses respond to ether and other organic solvents?
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Which microorganisms lack a cell wall?
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Which feature is absent in viruses?
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What is the primary function of the sex pilus in bacteria?
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What are the main components of bacterial spores that contribute to their resistance?
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Which of the following statements is true about fungi?
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Which component is primarily responsible for the rigidity of fungal cell walls?
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What type of reproduction gives rise to asexual spores in fungi?
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What is a distinguishing characteristic of the cell membrane in fungi?
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Which of the following is NOT a type of sexual spore produced by fungi?
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Which process describes how fungi obtain nutrients from their environment?
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Study Notes
Properties of Microorganisms
- Microorganisms are classified into four major groups: bacteria, fungi, protozoa, and viruses.
- Bacteria are prokaryotic organisms, while fungi and protozoa are eukaryotic.
- Viruses are acellular and require host cells for replication.
Prokaryotes vs. Eukaryotes
- Prokaryotic cells lack a nuclear membrane, whereas eukaryotic cells have a true nucleus.
- Prokaryotes have a single circular DNA molecule, while eukaryotes possess multiple linear chromosomes.
- Ribosome sizes differ: prokaryotes have 70 S ribosomes and eukaryotes have 80 S ribosomes.
- Prokaryotic cell walls contain peptidoglycan; eukaryotic cells do not.
Key Characteristics of Bacteria
- Bacteria are unicellular, with sizes typically ranging from 1μm to 3μm.
- Mycoplasma are the smallest bacteria, measuring around 0.2μm; Borrelia can be as large as 10μm.
- Bacteria can be categorized by shape: cocci (spherical), bacilli (rod-shaped), spirochaetes (spiral), or pleomorphic (variable shapes).
- Classification involves Gram staining, distinguishing between Gram-positive and Gram-negative bacteria.
Structural Properties of Bacteria
- Cell Wall: Composed of peptidoglycan, providing rigidity and protection. It is the target for antibiotics like aminoglycosides and tetracyclines.
- Nucleoid: Contains genetic material (DNA).
- Mesosome: Involves in cell division.
- Capsule: Polysaccharide layer that protects against phagocytosis.
- Pili/Fimbrae: Glycoprotein structures for attachment and conjugation.
- Flagellum: Protein structure used for motility.
- Spores: Provide resistance against harsh conditions; composed of keratin-like coatings.
- Plasmids: Extrachromosomal DNA that carries resistance and toxin genes.
Properties of Fungi
- Fungi are eukaryotic, non-photosynthetic, obligate or facultative aerobes.
- They secrete enzymes to degrade organic substrates for nutrient absorption.
- Fungi predominantly grow as mycelium (interlacing filaments) but can exist as yeasts (unicellular) or in a dimorphic form.
- Cell walls contain chitin, glucans, and mannans.
- Membrane contains ergosterol, a target for antifungal drugs (e.g., polyenes, azoles).
- Fungi reproduce via spores, which can be asexual (conidia, sporangiospores) or sexual (zygospores, ascospores, basidiospores).
- Their genome consists of either RNA or DNA, not both.
Properties of Viruses
- Viruses are composed of nucleic acid (either DNA or RNA) encased in a protein coat called a capsid, sometimes surrounded by a lipid envelope.
- They are inert outside host cells and can only replicate within living cells, making them obligate intracellular parasites.
Comparison of Microorganism Properties
- Viruses: Non-cellular, diameter of 0.02-0.2μm, lack ribosomes, replicate within host cells.
- Bacteria: Prokaryotic, 1-5μm in diameter, possess ribosomes, replicate by binary fission.
- Fungi: Eukaryotic, 3-10μm in diameter (yeasts), possess ribosomes, reproduce by budding or mitosis.
- Protozoa & Helminths: Eukaryotic, 15-25μm (trophozoites), possess ribosomes, exhibit various motility methods.
Assignment
- Study the Gram staining procedure and familiarize with its steps.
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Description
Explore the essential characteristics of microorganisms in this introductory lecture. Learn to differentiate between eukaryotes and prokaryotes, understand structural properties of bacteria, and discover their practical applications. Ideal for students in medical microbiology.
