Microbiology Exam 1 Study Guide: The Microbial World, Chemical Principles, Microscopy, and Cell Structure

Study Guide - Smart Notes

Tailored notes based on your materials, expanded with key definitions, examples, and context.

Chapter 1: The Microbial World and You

Introduction to Microbes

Microorganisms, or microbes, are organisms too small to be seen with the unaided eye. They are found everywhere and play essential roles in ecosystems, health, and disease.

Microorganism: An organism too small to be seen without magnification.
Microbiome: The community of microbes inhabiting a particular environment or host.
Normal microbiota: Resident microbes that live on or in the human body, often providing protection and benefits.
Transient microbiota: Microbes that temporarily inhabit the body.
Biofilm: A structured community of microbes attached to a surface and embedded in a self-produced matrix.

Types of Microorganisms

Prokaryote: A cell lacking a membrane-bound nucleus (includes Bacteria and Archaea).
Bacteria: Prokaryotes with characteristic cell walls containing peptidoglycan.
Archaea: Prokaryotes distinct from bacteria, often found in extreme environments.
Eukaryote: A cell with a nucleus and membrane-bound organelles (includes Fungi, Protozoa, Helminths).
Fungi: Eukaryotic organisms such as yeasts and molds that absorb organic nutrients.
Protozoa: Usually motile, unicellular eukaryotes.
Helminths: Parasitic worms studied in microbiology due to their disease-causing potential.

Acellular Infectious Agents

Acellular: Not composed of cells.
Virus: Genetic material (DNA or RNA) enclosed in a protein coat; requires a host cell to replicate.
Prion: Infectious misfolded protein causing neurodegenerative diseases.
Pathogenic: Capable of causing disease.
Infectious disease: Disease resulting from a pathogen overcoming host defenses.

Development of Microbiology

Cell theory: All living organisms are composed of cells.
Spontaneous generation: Disproven idea that life arises from nonliving matter.
Biogenesis: Living cells arise only from pre-existing cells.
Louis Pasteur: Demonstrated biogenesis with swan-neck flask experiments; developed fermentation and pasteurization.
Robert Koch: Linked specific microbes to specific diseases (Koch's postulates).
Aseptic technique: Procedures to prevent microbial contamination.
Germ theory: Microorganisms can cause disease.

Naming and Applications

Binomial nomenclature: Scientific naming system using Genus (capitalized) and species (lowercase), e.g., Escherichia coli.
Bacteriology: Study of bacteria.
Mycology: Study of fungi.
Parasitology: Study of protozoa and parasitic worms.
Virology: Study of viruses.
Immunology: Study of immune defenses.
Biotechnology: Use of organisms or their products for practical purposes.

Chapter 2: Chemical Principles

Atoms and Elements

All matter is composed of atoms, which are the smallest units retaining the properties of an element.

Atom: Smallest unit of an element.
Proton (+): Positively charged particle; defines the element.
Neutron (0): Neutral particle; contributes to atomic mass.
Electron (-): Negatively charged particle; occupies energy shells.
Atomic number: Number of protons in the nucleus.
Mass number: Total number of protons and neutrons.
Isotope: Atoms of the same element with different numbers of neutrons.

Chemical Bonds and Reactions

Valence shell: Outermost electron shell; determines chemical reactivity.
Ion: Atom or molecule with a net charge.
Ionic bond: Attraction between oppositely charged ions after electron transfer.
Covalent bond: Atoms share electron pairs.
Hydrogen bond: Weak attraction involving a polar hydrogen atom.
Activation energy: Minimum energy required to initiate a chemical reaction.
Synthesis reaction: Builds larger molecules from smaller ones.
Decomposition reaction: Breaks down molecules into smaller units.

Water, pH, and Energy

Water polarity: Water molecules have partial charges, making water an excellent solvent.
Acid: Proton donor; pH < 7.
Base: Proton acceptor; pH > 7.
Buffer: Substance that resists sudden changes in pH.
pH unit: Each unit represents a tenfold change in hydrogen ion concentration.
Endergonic reaction: Requires energy input.
Exergonic reaction: Releases energy.

Macromolecules

Monomer: Small molecular building block.
Polymer: Large molecule made of repeating monomers.
Dehydration synthesis: Joins monomers by removing water.
Hydrolysis: Splits polymers by adding water.
Carbohydrate: Sugars and starches; provide energy and structure.
Lipid: Nonpolar molecules for membranes and energy storage.
Protein: Polymers of amino acids; perform diverse cellular functions.
Nucleic acid: Polymers of nucleotides; store and transmit genetic information.

Information Molecules and Cellular Fuel

Amino acid: Protein monomer with a variable R group.
Peptide bond: Covalent bond linking amino acids in proteins.
Denaturation: Loss of protein structure and function due to environmental changes.
Nucleotide: Building block of nucleic acids; consists of a sugar, phosphate, and base.
DNA: Double-stranded molecule storing hereditary information.
RNA: Usually single-stranded; involved in protein synthesis and gene regulation.
ATP (Adenosine triphosphate): Immediate energy-transfer molecule in cells.

Key Equations

pH calculation:
ATP hydrolysis:

Chapter 3: Observing Microorganisms Through a Microscope

Principles of Microscopy

Microscopy allows visualization of microorganisms and their structures using magnification and contrast techniques.

Magnification: Increases the apparent size of an image.
Total magnification: Product of ocular and objective lens magnifications.
Resolution: Ability to distinguish two points as separate entities.
Contrast: Difference in light intensity between specimen and background.
Immersion oil: Used with high-power objectives to reduce light refraction and improve resolution.
Micrometer: meters.
Nanometer: meters.

Types of Light Microscopy

Brightfield: Dark specimen on a bright background; most common.
Darkfield: Bright specimen on a dark background; useful for live, unstained samples.
Phase contrast: Enhances contrast in living, unstained cells by amplifying differences in refractive index.
DIC (Differential Interference Contrast): Produces high-contrast, 3D-like images of living cells.
Fluorescence: Uses fluorescent dyes to visualize specific structures.
Confocal: Combines optical slices to create a 3D image.

Electron and Probe Microscopy

Electron microscope: Uses electron beams for much higher resolution than light microscopes.
TEM (Transmission Electron Microscopy): Electrons pass through thin sections; reveals internal structures.
SEM (Scanning Electron Microscopy): Electrons scan the surface; produces 3D-like images of exteriors.
Electron microscopy: Requires dead specimens and a vacuum environment.
Atomic force microscopy: Uses a physical probe to map surfaces at the atomic level.

Specimen Preparation and Staining

Smear: Thin film of microbes on a slide.
Fixation: Attaches, kills, and preserves cells on a slide.
Basic dye: Positively charged chromophore stains cells.
Acidic dye: Negatively charged chromophore stains the background.
Simple stain: Uses one dye to show cell size, shape, and arrangement.
Differential stain: Uses multiple reagents to distinguish between groups of organisms.
Special stain: Highlights specific structures (e.g., capsules, endospores, flagella).

Diagnostic Stains

Gram stain: Differentiates bacteria based on cell wall structure.
Gram positive: Thick peptidoglycan retains purple dye.
Gram negative: Thin peptidoglycan; decolorizes and stains pink/red.
Gram stain order: Crystal violet, iodine, alcohol, safranin.
Acid-fast stain: Detects waxy, mycolic acid-rich cell walls (e.g., Mycobacterium).
Capsule stain: Reveals a clear halo around the cell.
Endospore stain: Stains endospores green and cells red.
Flagella stain: Uses a mordant to thicken flagella for visibility.

Chapter 4: Functional Anatomy of Prokaryotic and Eukaryotic Cells

Shared Cell Structures

All cells share certain basic structures that are essential for life.

Plasma membrane: Selective barrier surrounding the cytoplasm.
Cytoplasm: Aqueous interior where metabolism occurs.
Ribosome: Site of protein synthesis.
Genome: Complete set of genetic information.
Prokaryote: Lacks membrane-bound nucleus and organelles.
Eukaryote: Has a nucleus and membrane-bound organelles.

Bacterial Cell Exterior

Glycocalyx: External sugar coat for attachment or protection.
Capsule: Organized glycocalyx that resists phagocytosis.
Flagellum: Rotating structure for motility.
Axial filament: Internal flagella producing spirochete motion.
Fimbriae: Short appendages for attachment.
Pilus: Structure for DNA transfer between bacterial cells (conjugation).

Bacterial Cell Envelope

Peptidoglycan: Polymer forming the bacterial cell wall.
Gram positive: Thick peptidoglycan layer with teichoic acids.
Gram negative: Thin peptidoglycan plus an outer membrane.
LPS (Lipopolysaccharide): Endotoxin in Gram-negative outer membrane.
Periplasm: Space between Gram-negative membranes.
Acid-fast wall: Contains waxy mycolic acid.
Osmotic lysis: Cell bursts when water enters an unprotected cell.

Internal Structures of Prokaryotes

Nucleoid: Region containing the bacterial chromosome.
Plasmid: Small, independently replicating DNA molecule.
70S ribosome: Bacterial protein synthesis machinery.
Inclusion: Stored nutrient or specialized material.
Endospore: Dormant, resistant survival structure.
Binary fission: Asexual division producing two cells.
Selective permeability: Controlled movement of substances across the membrane.

Eukaryotic Microbial Structures

Nucleus: Membrane-bound compartment containing DNA.
80S ribosome: Eukaryotic cytoplasmic ribosome.
Endoplasmic reticulum (ER): Synthesizes proteins (rough ER) or lipids (smooth ER).
Golgi apparatus: Modifies, sorts, and ships cell products.
Lysosome: Organelle containing digestive enzymes.
Mitochondrion: Site of aerobic ATP production.
Chloroplast: Site of photosynthesis in algae.
Fungal wall: Mainly composed of chitin; algal walls vary in composition.