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2: Microbial Structure

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  • Page ID
    42471

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    Jump to Chapter Contents ↓

    In the 17th century, observations of microscopic life led to the development of the cell theory: the idea that the fundamental unit of life is the cell, that all organisms contain at least one cell, and that cells only come from other cells. Despite sharing certain characteristics, cells may vary significantly. The two main types of cells are prokaryotic cells (lacking a nucleus) and eukaryotic cells (containing a well-organized, membrane-bound nucleus). Each type of cell exhibits remarkable variety in structure, function, and metabolic activity.

    Viruses are not cells, but are biological entities with some similarities to cells.  Viruses also have a wide variety of structures and replication strategies, but unlike cells they do not metabolize and require a host cell to replicate.

    Chapter 2 BIOL 235 Learning Outcomes

    • Compare and contrast cellular (living) microbes, viruses, and prions based on their structures, genetic material, and mechanisms of replication.
    • Explain the difference between the terms prokaryotic and eukaryotic.
    • Compare and contrast "prokaryotic" (bacterial) cell structure with eukaryotic cell structure with respect to typical size, cell boundary, and presence/absence of various intracellular compartments.
    • Describe the function of the following major eukaryotic intracellular structures: ribosomes, mitochondria, nucleus, Golgi apparatus.
    • Describe the structural similarities between bacterial and eukaryotic plasma membranes.
    • Recognize and apply the terms for bacterial cell morphologies and arrangements.
    • Describe in words and sketch the important features of the bacterial peptidolycan (murein) incluing N-acetyl-muramic acid (NAM), N-acetyl-glucosamine (NAG), amino acids, and peptide crosslinks.
    • Explain the importance of peptide crosslinking in peptidoglycan (murein) structure
    • Compare and contrast (in words and diagrammatically) Gram-positive and Gram-negative cell envelopes including: peptidoglycan structure, teichoic acid, Braun's lipoprotein, lipopolysaccharide (and its components lipid A and O-side chains), outer membrane, plasma membrane, porins
    • Explain at the cellular/moelcular level why Gram-positive cells stain purple and Gram-negatives pink in the Gram stain (also discussed in lab)
    • Name a genus of bacteria that naturally lacks a cell wall
    • Explain how the cell wall of Mycobacterium differs from other Gram-positive bacteria
    • Describe structure and function bacterial appendages outside the cell wall including: flagella, pili, fimbrae, and glycocalyx (slime layer, capsule).
    • Explain how bacterial cellular structures aid in the pathogenicity of some organisms. Discuss specifically: LPS (a.k.a LOS), capsules, fimbrae/pili, and endospores.
    • Identify what bacterial cell structure is also called endotoxin, what kind of bacteria it is found in, and it's effects when it is present in the bloodstream.
    • Describe the generalized structure of a viral particle including location and molecular make-up of genetic material, capsid, and envelope.
    • Recognize and identify the most common capsid shapes.
    • Provide two examples of the importance of protein folding and binding specificity in the replication of certain pathogens.

    • 2.1: Foundations of Modern Cell Theory
      This page outlines the development of cell theory and endosymbiotic theory, highlighting contributions from scientists like Hooke and Margulis. Cell theory states that all cells arise from existing cells and are life's fundamental units. Endosymbiotic theory explains that eukaryotic organelles like mitochondria and chloroplasts originated from prokaryotic bacteria through symbiosis, supported by genetic and structural similarities.
    • 2.2: Shared Characteristics of Cell Structure
      This page covers the essential elements of cells, focusing on the distinctions between prokaryotic and eukaryotic cells. It notes that all cells have cytoplasm, DNA, mRNA, and ribosomes, but differ in size and structure; prokaryotic cells lack a nucleus and have a single circular chromosome, whereas eukaryotic cells possess a nucleus with multiple rod-shaped chromosomes.
    • 2.3: Unique Characteristics of Prokaryotic Cells
      This page provides an overview of prokaryotic cell structures and functions, emphasizing their lack of a nucleus and membrane-bound organelles but complex internal structures. It highlights transport mechanisms, including facilitated diffusion and active transport, and explores bacterial cell wall composition, including peptidoglycan and differences in Gram-positive and Gram-negative bacteria.
    • 2.4: Unique Characteristics of Eukaryotic Cells
      This page examines eukaryotic and prokaryotic cells, distinguishing eukaryotic features like a nucleus, organelles, and ribosome differences relevant for antibiotic targeting. It details the endomembrane system, including the rough and smooth ER, Golgi apparatus, and lysosomes for cellular synthesis and transport. The endosymbiotic theory explains the origins of mitochondria and chloroplasts.
    • 2.5: Viral Structue and Prions
      This page covers the structure and classification of viruses, noting their acellular nature and dependence on host cells. It describes viral components, capsid shapes, and the significance of glycoprotein spikes. It differentiates between enveloped and non-enveloped viruses and discusses the various types of viral nucleic acids. It also introduces prions, which cause transmissible spongiform encephalopathies (TSEs), neurodegenerative disorders marked by brain degeneration and dementia.

    Thumbnail: "File:Prokaryote cell.svg" by This vector image is completely made by Ali Zifan is licensed under CC BY-SA 4.0

  • Page ID
    42471

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