BIOL 2303 Lecture Notes - Lecture 3: Gram-Negative Bacteria, Gram-Positive Bacteria, Spirochaete
7 Feb 2018
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Document Summary
Microbes are small- but there is substantial variation in size: smallest: mycoplasma pneumoniae- 0. 2 m diameter, biggest: thiomargarita namibiensis: 750 m diameter (visible to the naked eye) Variation in cell volume is ~600 million-fold- roughly the equivalent to the size of a blue wale (~19 000kg) to a firebrat (~30mg) Size matters: ratio of surface area to volume. Cell morphology: overall shape and appearance of cells. Common shapes: coccus, rod- bacillius, spirilla, other: spirochaetes, appendaged, filamentous. The cytoplasm is separated from the environment by the cell membrane and the cell wall. Selective permeability: let some molecules in, keep others out. Phospholipid: hydrophilic end (glycerol-phosphate, hydrophobic end (fatty acid) Membrane proteins: may contact the cytoplasm, the external environment, or both. Integral proteins are firmly embedded: peripheral proteins are associated with the membrane, but not embedded. Anchor proteins: transport proteins carry solutes across the membrane against the concentration gradient, transport is often highly specific and highly regulated.
