Outline 7.doc

Outline 7 - Prokaryotic Cells I. General characteristics A. Lack true nucleus and many organelles inside cell B. single celled organisms C. Kingdom Monera of 5-kingdom system D. split into Eubacteria and Archaea in 3 domain system E. most have protein cell wall II. Bacterial shapes, arrangement, size A. Shapes 1. coccus 2. bacillus 3. curved: vibrio, spirillum, spirochete 4. varied - pleomorphism B. Arrangement 1. by number 2. by grouping: staphylo-, strepto-, sarcina, palisades C. Size - most are 0.2 µm ? 3.0 µm (spirochetes may reach 250 µm length) III. Prokaryotic cell structure A. External features 1. Flagella: for movement, esp. chemotaxis; attached by hook and basal body monotrichous ? 1 lophotrichous ? several together amphitrichous ? flagella at each end peritrichous ? multiple random periplasmic ? curl against cell 2. Pili (pilus) ? cytoplasmic extension, exchange of DNA during conjugation 3. Fimbriae: extensions from surface sticky 4. Other surface structures: Slime layer - carbohydrates - protect cell against water and nutrient loss Glycocalyx ? dense layer of carbohydrates- coats cell and helps it adhere Capsule ? some make a carb, protein, or glycoprotein capsule Any of these may assist cells in forming biofilms. B. Cell envelope (wall) (coat) ? the boundary layer of cell 1.Peptidoglycan ? net of G (glucosamine) and M (muramic acid) molecules with M-M crosslinks 2. Gram-positive wall: open-faced sandwich - two layers: thick peptidoglycan cell wall, and a cell membrane 3. Gram-negative wall: complete sandwich - three layers: outer membrane, thin peptidoglycan cell wall, and cell membrane; more difficult to kill. 4. Some prokaryotes - different cell walls with extra lipid molecules ? stain with acid-fast stain; Ex. Mycobacterium tuberculosis and M. Leprae; C. Internal structure Cytoplasm? thick solution inside cell