Cell Anatomy + Theories
Gram Staining
A means of bacterial identification in which cells are stained, rinsed, and counterstained so as to provide a means of classification.
Developed by Hans Gram, 1884
violet cells are Gram positive
red cells are Gram negative
Structural Qualities
Gram positive cell walls: thick (20-80 nanometers), single-layered cell wall composed primarily of peptidoglycan
Gram negative cell walls: thin (8-11 nanometers), double-layered cell wall. Outer layer is a lipid bilayer, inner layer is a thin peptidoglycan wall
endospores: dormant body produced by some Gram-positive bacteria used to survive adverse conditions
—>function in survival, not reproduction. capable of withstanding harsh extremes, metabolically inactive, contains minimum structures and chemicals necessary to guide life processes
Theories and Postulates
Koch’s Postulates
Outlined by Robert Koch in 1884.
A series of steps, utilized sequentially to provide proof via experimentation.
Proved that specific microorganisms cause specific diseases
Not only proved the Germ Theory of Disease, but also stressed the importance of pure laboratory cultures in the identification of microorganisms. Still used to this day.
Cell Structure and Anatomy
Prokaryotes
General Prokaryotic Cell Structure
Small (1-5 micrometers) with a simple cytoplasmic membrane
Lack specialized structures such as a nucleus (single chromosome) and membrane-bound organelles
All unicellular microorganisms, that fall into the kingdom Monera (Prokaryotae)
Earliest cells to appear on earth
Original ancestors of modern bacteria and eukaryotic organisms
Parts and Organelles
Cell envelope: extensive, chemically-complex external covering that accounts for up to ½ of prokaryote’s cell volume. Composed of multiple layers stacked on top of each other, often tightly bound, acting as a single protective unit (glycocalyx, cell wall, and cytoplasmic cell membrane)
—> glycocalyx is the outermost layer, exposed to severe environmental conditions. It is a coating of macromolecules that protect the cell and help it adhere to its surroundings, consisting of the motile slime layer and the protective capsule
Cell wall: rigid, intermediate layer of envelop which determines the shape of the bacterium and provides structural support.
—>Composed of macromolecule known as peptidoglycan (hallmark of prokaryotic cell construction), yielding an extremely strong, yet somewhat flexible framework. —>Prevents lysis of cells due to increased internal pressure, and determines whether cells are Gram positive or negative
Cytoplasmic cell membrane: innermost layer of the cell membrane. A thin (5-10 nanometer) flexible sheath molded completely around cell’s protoplasm. Phospholipid bilayer with embedded proteins.
—>Primary function is that of regulating passage of substances into the cell and the discharge of wastes, also does respiration, synthesis of structural macromolecules and biochemicals, and secretion
—>Mesosomes: invaginations of the cell membrane extending into the protoplasm; increases surface area upon which reactions can occur
Flagella: appendages that provide self-propulsion for cells in aqueous environments. Consists of three parts, a filament, hook/sheath, and basal body. Construction allows the filament to rotate 360*, causing the cell to rotate in the opposite direction, providing forward movement
—>monotrichous: single flagella at one pole
—>amphitrichous: single flagellum at each pole
—>lophotrichous: tufts of flagella at one or both poles
—>peritrichous: flagella are dispersed uniformly of the entire cell surface
Prokaryotic ribosomes: tiny, discrete spherical structures composed of protein subunits and RNA. May be suspended freely in protoplasm, or affixed to the cytoplasmic membrane or mesosomes. Occur singly or in polysome chains. Serve as sites for protein synthesis within cells. Smaller and less dense than eukaryotic ribosomes
Special Traits
Toxins: chemical substances produced by microorganisms, which prove harmful to other organisms, host cells, and/or tissues
—>exotoxins: poisonous substances produced intracellularly by certain bacterial cells, and subsequently released by the living cells into the surrounding extracellular space. Highly soluble in body fluids, and easily disseminated throughout the body via circulation. May be categorized as neurotoxins, enterotoxins, or cytotoxins
—>endotoxins: poisonous substances produced intracellularly and subsequently incorporated into the cell wall of certain bacteria. Essentially intracellular toxins that are released when the bacterium dies and its cell wall dissolves. Rapidly and easily disseminated throughout the body via circulation
Eukaryotes
General Eukaryotic Cell Structure
Large cells (10-100 micrometers) with a complex cytoplasmic membrane
present with a true nucleus (multiple chromosomes) and complex, membrane bound organelles
may be unicellular organisms or part of a large, multicellular organism
Comprise the plants, animals, fungi, and protozoa
Originally developed from more-primitive prokaryotes
Organelles
plastid: membrane-bound structures containing photosynthetic pigments, found only in plant cells. Energy-producing organelles known to be the sites of photosynthesis. Chloroplasts (type of plastid) contain chlorophyll that converts light energy into chemical energy
Cell Anatomy + Theories
Gram Staining
A means of bacterial identification in which cells are stained, rinsed, and counterstained so as to provide a means of classification.
Developed by Hans Gram, 1884
violet cells are Gram positive
red cells are Gram negative
Structural Qualities
Gram positive cell walls: thick (20-80 nanometers), single-layered cell wall composed primarily of peptidoglycan
Gram negative cell walls: thin (8-11 nanometers), double-layered cell wall. Outer layer is a lipid bilayer, inner layer is a thin peptidoglycan wall
endospores: dormant body produced by some Gram-positive bacteria used to survive adverse conditions
—>function in survival, not reproduction. capable of withstanding harsh extremes, metabolically inactive, contains minimum structures and chemicals necessary to guide life processes
Theories and Postulates
Koch’s Postulates
Outlined by Robert Koch in 1884.
A series of steps, utilized sequentially to provide proof via experimentation.
Proved that specific microorganisms cause specific diseases
Not only proved the Germ Theory of Disease, but also stressed the importance of pure laboratory cultures in the identification of microorganisms. Still used to this day.
Cell Structure and Anatomy
Prokaryotes
General Prokaryotic Cell Structure
Small (1-5 micrometers) with a simple cytoplasmic membrane
Lack specialized structures such as a nucleus (single chromosome) and membrane-bound organelles
All unicellular microorganisms, that fall into the kingdom Monera (Prokaryotae)
Earliest cells to appear on earth
Original ancestors of modern bacteria and eukaryotic organisms
Parts and Organelles
Cell envelope: extensive, chemically-complex external covering that accounts for up to ½ of prokaryote’s cell volume. Composed of multiple layers stacked on top of each other, often tightly bound, acting as a single protective unit (glycocalyx, cell wall, and cytoplasmic cell membrane)
—> glycocalyx is the outermost layer, exposed to severe environmental conditions. It is a coating of macromolecules that protect the cell and help it adhere to its surroundings, consisting of the motile slime layer and the protective capsule
Cell wall: rigid, intermediate layer of envelop which determines the shape of the bacterium and provides structural support.
—>Composed of macromolecule known as peptidoglycan (hallmark of prokaryotic cell construction), yielding an extremely strong, yet somewhat flexible framework. —>Prevents lysis of cells due to increased internal pressure, and determines whether cells are Gram positive or negative
Cytoplasmic cell membrane: innermost layer of the cell membrane. A thin (5-10 nanometer) flexible sheath molded completely around cell’s protoplasm. Phospholipid bilayer with embedded proteins.
—>Primary function is that of regulating passage of substances into the cell and the discharge of wastes, also does respiration, synthesis of structural macromolecules and biochemicals, and secretion
—>Mesosomes: invaginations of the cell membrane extending into the protoplasm; increases surface area upon which reactions can occur
Flagella: appendages that provide self-propulsion for cells in aqueous environments. Consists of three parts, a filament, hook/sheath, and basal body. Construction allows the filament to rotate 360*, causing the cell to rotate in the opposite direction, providing forward movement
—>monotrichous: single flagella at one pole
—>amphitrichous: single flagellum at each pole
—>lophotrichous: tufts of flagella at one or both poles
—>peritrichous: flagella are dispersed uniformly of the entire cell surface
Prokaryotic ribosomes: tiny, discrete spherical structures composed of protein subunits and RNA. May be suspended freely in protoplasm, or affixed to the cytoplasmic membrane or mesosomes. Occur singly or in polysome chains. Serve as sites for protein synthesis within cells. Smaller and less dense than eukaryotic ribosomes
Special Traits
Toxins: chemical substances produced by microorganisms, which prove harmful to other organisms, host cells, and/or tissues
—>exotoxins: poisonous substances produced intracellularly by certain bacterial cells, and subsequently released by the living cells into the surrounding extracellular space. Highly soluble in body fluids, and easily disseminated throughout the body via circulation. May be categorized as neurotoxins, enterotoxins, or cytotoxins
—>endotoxins: poisonous substances produced intracellularly and subsequently incorporated into the cell wall of certain bacteria. Essentially intracellular toxins that are released when the bacterium dies and its cell wall dissolves. Rapidly and easily disseminated throughout the body via circulation
Eukaryotes
General Eukaryotic Cell Structure
Large cells (10-100 micrometers) with a complex cytoplasmic membrane
present with a true nucleus (multiple chromosomes) and complex, membrane bound organelles
may be unicellular organisms or part of a large, multicellular organism
Comprise the plants, animals, fungi, and protozoa
Originally developed from more-primitive prokaryotes
Organelles
plastid: membrane-bound structures containing photosynthetic pigments, found only in plant cells. Energy-producing organelles known to be the sites of photosynthesis. Chloroplasts (type of plastid) contain chlorophyll that converts light energy into chemical energy
