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Transcript
! " " # Terms you should know: organelles membrane-bounded organelles mitochondria nucleus nucleoid endosymbiotic theory cell wall peptidoglycan cellulose cocci bacilli envelope Gram-positive Gram-negative teichoic acid outer membrane lipopolysaccharide periplasm mycoplasmas porins capsule flagella chemotaxis Questions you should be able to answer: • What are some key differences between prokaryotic and eukaryotic cells? • Why do the specialized organelles of a eukaryotic cell allow for greater size and complexity? • How did mitochondria probably originate? • Describe the structures of Gram-positive and Gram-negative cell walls. • Are Gram-positive or Gram-negative bacteria generally more susceptible to drugs? Why? • How does the Gram stain work? Characteristics of all cells: • How do bacteria move toward nutrients? Cell membrane (phospholipid bilayer + proteins) DNA (genetic material: information to make proteins) Lecture outline: Ribosomes (organelle that synthesizes proteins) Same basic chemical composition (DNA, proteins, etc.) I. Prokaryotic vs. eukaryotic cells: A. The importance of size B. Organelles 1. Nucleus 2. Mitochondria 3. Ribosomes C. The endosymbiotic theory D. Cell walls Cytoplasm Prokaryotic Cells Eukaryotic Cells Peptidoglycan cell wall Cellulose cell wall (plants & DNA in cytoplasm (nucleoid) DNA in nucleus Single, circular chromosome Multiple, linear chromosomes No membrane-bounded organelles Membrane-bounded organelles Generally very small (1-5 µm) Relatively large (10-100 µm) 70S ribosomes 80S ribosomes II. Prokaryotic envelope structure: A. Bacterial shapes: cocci, bacilli, curved or spiral B. Cell wall protects cells from bursting Cell membrane C. Gram-positive vs. Gram-negative envelope Peptidoglycan cell wall D. Capsule: external polysaccharide layer Outer membrane Periplasm 1. Enables bacteria to stick to surfaces Teichoic acid 2. Escape destruction by white blood cells III. Prokaryotic cell structure Gram-positive Gram-negative yes yes thick thin no yes no yes yes no Lipopolysaccharide no yes Color in Gram stain purple pink A. Flagella: motility and chemotaxis 1. Counterclockwise rotation produces straight “runs” 2. Clockwise rotation produces random “tumbles” 3. Presence of nutrients favors runs
