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Transcript
Prokayotic vs Eukaryotic Cells Functional Anatomy Typical Bacterial Cell Typical Eukaryotic Cells Prokaryote vs Eukaryote Overview Prokaryote or “before nucleus” – no membrane-bound nucleus – no other membrane-bound organelles – DNA not associated with histones – cell walls almost always contain peptidoglycan – 70s ribosomes – Largest about size of smallest eukaryote Eukaryote or “true nucleus” – membrane bound nucleus – many other membranebound organelles – DNA associated with histones – cell walls never contain peptidoglycan – 80s ribosomes – Smallest about size of largest prokaryote Prokaryotic Cells Size – Smallest of living cells » 0.2 to 2.0 μm in diameter » 2 to 8 μm in length – Most eukaryotes bigger – Viruses much smaller Common Bacterial Shapes Cocci - spherical Bacilli – rods Spirillum - spiral Other, Less Common Shapes Vibrio – comma Coccobacillus Square Star - Common Cell arrangements Cocci Bacilli Prokaryotic Anatomy from the Outside In Glycocalyx Appendages Cell Wall Bacterial Cell Membranes Inside the Cell Glycocalyx Sticky substances that surround cells – Firmly attached = capsule – Loosely attached = slime layer Composition varies with species – Polysaccharides – Polypeptides – Both Function – Protect cell from phagocytosis and dehydration – Aid in attachment to various surfaces – May inhibit movement of nutrients from cell Appendages Flagella – Tail-like structures extending out from glycocalyx – Functions in movement of the bacterial cell – Complex structure Structure of Flagella Filament – Long tail-like region – Constant diameter – Made of protein Hook – Filament attachment Basal body – Small central rod inserted into a series of rings Cell Wall Rigid Composed mostly of peptidoglycan – Found only in bacterial cell walls – Amount differs in gram+ and gram- cells Protects cell in environments with osmotic pressures Peptidoglycan Glycan portion – NAG » N-acetylglucosamine – NAM » N-acetylmuramic acid – Linked in rows of 10-65 sugars Peptide portion – Adjacent rows are linked by polypeptides Gram+ Cell Wall Gram – Cell Wall Atypical Cell Walls Mycoplasmas – Lack cell wall – Smallest known bacteria Archeobacteria – Cell walls contain pseudomurein rather than peptidoglycan – Lacks D-amino acids found in bacteria L-forms – Tiny mutant bacteria with defective cell walls – Just enough material to prevent lysis in dilute environments Inside the Cell Wall Cell Membrane Cytoplasm – 4/5 water and 1/5 dissolved substances – Most chemical reactions occur here Ribosomes – Abundant in cytoplasm – 70s Nuclear region – Central 10% of cell volume – DNA in single circular chromosome Inclusions – small bodies within cytoplasm – Many different types
