Cell Structure and Function Quiz

Cell Structure and Function

• Cell Membrane: Phospholipid bilayer with proteins; selectively permeable; involved in signal transduction.
• Cell Wall:
  • Bacteria: Peptidoglycan.
  • Archaea: Pseudomurein or S-layer proteins.
  • Eukaryotes: Cellulose (microalgae), chitin (fungi).
• Flagella: Motility structures; different structures in bacteria (rotary) and eukaryotes (whip-like).
• Pilus/Fimbria: Attachment and conjugation structures.
• Nucleoid: Bacterial/archaeal DNA region.
• Cytoplasm: Site of metabolic activity.
• Specialized Structures:
  • Gas Vesicles: Buoyancy.
  • Endospores: Survival in harsh conditions (e.g., Bacillus, Clostridium).
  • Carboxysomes: CO2 fixation.
  • Eyespots: Light detection (eukaryotic algae).
• Gram (+): Thick peptidoglycan; teichoic acids; purple stain.
• Gram (-): Thin peptidoglycan, outer membrane with LPS; pink stain.
• Acid-Fast: Mycolic acids; Ziehl-Neelsen staining (e.g., Mycobacterium).
• Viral Structures:
  • Capsid: Protein shell; helical or icosahedral.
  • Envelope: Lipid bilayer (not all viruses).
  • Genome: DNA or RNA, single- or double-stranded.
• Locomotion:
  • Swimming: Flagellar motion.
  • Gliding: Surface contact motility.
  • Chemotaxis: Movement in response to chemical gradients.
  • Phototaxis: Movement toward light.

Culture and Growth

• Culturing Bacteria: Methods for growing bacteria.
  • Liquid cultures: Growth rate studies.
  • Solid media: Isolation of colonies.
• Media:
  • Selective: Inhibits unwanted microbes.
  • Differential: Distinguishes microbes based on biochemical properties.
• Bacterial Growth Curves:
  • Lag Phase: Adaptation.
  • Log Phase: Exponential growth.
  • Stationary Phase: Nutrient depletion.
  • Death Phase: Decline.
• Cell Population Calculations:
  • CFU (Colony-Forming Units).
  • Optical Density: Proportional to cell density.

Antibiotics and Resistance

• Antibiotics:
  • Classes: Penicillins (target cell wall synthesis), Tetracyclines (inhibit protein synthesis).
• Resistance Mechanisms: Efflux pumps, target modification, enzymatic degradation.

Sterilization and Disinfection

• Techniques:
  • Heat (autoclaving): Best for sterilizing heat-resistant items and media.
  • Radiation (UV): Ideal for surface sterilization and air disinfection.
  • Filtration: For sterilizing heat-sensitive items.
  • Chemicals (alcohol, bleach): Effective for disinfecting surfaces, equipment, and hands.

Limitations of Culture-Based Approaches

• Misses unculturable microbes; biased towards fast-growing species.

Molecular Biology

• Bacterial Cell Division: Binary Fission; DNA replication begins at the origin. Key proteins: DnaA, DNA polymerase.
• Transcription and Translation:
  • Transcription: Enzyme RNA polymerase, promoters, and terminators.
  • Translation: Ribosomes, tRNA, codons.
• Gene Regulation (lac and trp Operons): Lac Operon (inducible, activated by lactose), Trp Operon (repressible, turned off by tryptophan).
• Recombinant DNA: Applications include producing insulin and GMOs.

Metabolism and Applications

• Metabolic Strategies:
  • Energy Sources: Phototrophs (light), Chemotrophs (chemical compounds)
  • Carbon Sources: Autotrophs (CO2), Heterotrophs (organic compounds).
• Key Processes: Fermentation, Photosynthesis, Nitrogen Fixation.
• Applications: Fermentation (bread, soy sauce, sauerkraut).

Evolution and Ecology

• Endosymbiotic Theory: Origin of mitochondria and chloroplasts from ancient symbiotic bacteria.
• Adaptations to Extremes: Temperature, salinity, pH.
• Lytic and Lysogenic Viral Life Cycles:
  • Lytic Cycle: Virus infects, hijacks machinery, produces new viruses, results in host cell lysis.
  • Lysogenic Cycle: Viral genome integrates into host DNA, remains dormant, environmental triggers may induce lytic cycle
• Genomic Analysis: Comparative genomics reveals evolutionary relationships; identification of genes.
• Horizontal Gene Transfer Mechanisms: Transduction, conjugation, transformation, and role in evolution.

16S Amplicon Sequencing & Microbial Community Interactions

• 16S Amplicon Sequencing: Determine bacterial community composition, Measure diversity.
• Microbial Community Interactions: Cooperation/mutualism (beneficial for both), commensalism (one benefits, other unaffected), predation, parasitism (one benefits, other harmed).

Advanced Sequencing Techniques

• Metagenomics, Metatranscriptomics, Metaproteomics, Metabolomics.

Bacterial Defense Mechanisms

• Restriction-Modification Systems: Restriction enzymes cleave foreign DNA at specific sites, host DNA protected by methylation.
• CRISPR-Cas Systems: Adaptive immunity; stores viral DNA sequences, Cas proteins recognize and cleave matching viral DNA during subsequent infections.

Microbes and Agents List

• Bacteria: Examples given of specific bacterial species and their characteristics.
• Archaea: Examples of specific archaea species and their characteristics.
• Eukaryotes: Examples of species with features (e.g., types of organisms, their characteristics like ability to produce toxins; e.g., Plasmodium falciparum, causes malaria.).
• Viruses: Examples of specific viruses and their characteristics (e.g., types of viruses causing diseases).

Test your knowledge on cell structures and their functions. This quiz covers topics such as cell membranes, walls, and specialized structures found in bacteria, archaea, and eukaryotes. Prepare to delve into the details of motility, metabolic activities, and staining techniques!