BIOL 209 1st Edition Lecture 4 Outline of Last Lecture I. BiomacromoleculesA. Question/answerB. CarbohydratesC. LipidsD. Nucleic Acids1. DNA2. RNAE. ProteinsF. Question/answerII. Prokaryotic Cell StructureOutline of Current Lecture I. The Cell WallA. Question/answerB. Bacterial Cell WallC. Question/answerD. Non-typical Cell WallsII. EnvelopesA. Gram +B. Gram – III. Cell Wall StainingA. Gram StainingB. Acid-Fast StainingCurrent LectureI. The Cell WallA. Question: If you took one of your epithelial cells and dropped it into a glass of drinking water what would happen?Answer: The cell would swell and burst because of hypotonic conditions1. Cell walls protect from osmolysis (cells bursting). Because an epithelial cell (animal cell) and therefore has no cell wall, it bursts.B. Bacterial Cell Wall1. A porous sheath (think of a window screen) that consists of a single, interlinked molecule2. Made of peptidoglycana. Glycan chains are composed of alternating N-acetyl glucosamine and N-acetyl muramic acidThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- A short peptide bridge links glycan chainsC. Question: Bacterial cell walls are usually composed of chains of what?Answer: Carbs linked together by peptidesD. Non-typical Cell Walls1. Mycobacterium have a unique mycolic acid-containing walla. Provides resilience and virulenceb. Serves as bases for identifying and treating mycobacterial infections2. Question: What class of biomacromolecule is mycolic acid most similar to?Answer: LipidsII. EnvelopesA. Gram + (Firmiculates)1. Thick peptidoglycan cell wall with a single cell membrane underneath2. Cell wall contains lipoteichoic acid and teichoic acid that anchors the cell wallB. Gram – (Proteobacterials)1. Thin peptidoglycan cell wall with two cell membranes sandwiching the peptidoglycan on either side2. Lipopolysaccharide (LPS) provides adherence function and is located on the outer membranea. Outer membrane restricts access to peptidoglycan based on size3. Active transport occurs at inner membraneIII. Cell Wall Staining – bacteria can be characterized by staining of their cell wallA. Gram staining: mechanism using dye binding to reveal cell structure1. Positively charged Crystal violet binds tightly to cells with a thick peptidoglycan layer, so Gram + cells retain the dye (remain purple) after washing2. Stepsa. Crystal violet stains cells to purpleb. Gram’s iodine applied- Gram’s iodine is more distinctly seen in Gram + cells because of the thicker membrane it is being trapped inc. Alcohol rinse applied- It dissolves lipids in the outer membrane and removes dye from Gram - cellsd. Counter stain applied to clear cell- Safranin, a red stain, is applied to detect Gram – cellsB. Acid-fast staining: Dye binds mycolic acid and is retained despite acid wash1. Carbolfuchsin is used to stain mycobacterium
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