Prokaryotic External Structure and Function Flashcards
Prokaryote Characteristics (5)
- Circular chromosome
- No histones; archaea have histone-like proteins
- No organelles
- Peptidoglycan (murein) cell walls in bacteria; pseudomurein cell walls in archaea
- Divide by binary fission
Eukaryote Characteristics (5)
- Paired chromosomes in nuclear membrane
- Histones
- Organelles
- Polysaccharide cell walls (when present)
- Divide by mitosis
Bacillus
Rod shaped
Coccus
Sphere shaped
Spirillum
Spiral shaped
Spirochaete
Corkscrew shaped
Glycocalyx
Capsule: organized polysaccharide, difficult to remove, firmly attached to cell wall
Slime: disorganized polysaccharide, easy to remove, loosely attached to cell wall
Peptidoglycan
Polymer of disaccharide made up of N-acetylglucosamine (NAG) with a B-1,4 linkage to N-acetylmuramic acid (NAM)
Gram-Positive Cell Wall
Peptidoglycan linked by polypeptides and supported by techoic acid
Gram-Negative Cell Wall
Peptidoglycan linked by polypeptides with an outer LPS layer; contains a periplasmic space and outer membrane to confer protection
LPS
Lipopolysaccharide; Consists of Lipid A, a core polysaccharide, and a variable o-polysaccharide antigen; confers negative charge and repels hydrophobics
Gram Positive (9)
- Thick peptidoglycan
- Abundant techoic acids
- No periplasmic space
- Limited LPS
- Low lipid content
- Resistant to mechanical stress
- Better in dry conditions
- Highly susceptible to lysozymes
- Penicillin sensitive
Gram Negative (10)
- Thin peptidoglycan
- No techoic acids
- Periplasmic space
- Outer membrane
- Abundant LPS
- High lipid content
- Susceptible to mechanical stress
- Excel in host intestines
- Low susceptibility to lysozyme
- Low susceptibility to penicillin
Bacteria Example without Peptidoglycan
Planctomycetes; protects it from certain DNA damaging metabolites
Mycoplasmas Cell Wall
No cell wall; have sterols in plasma membrane
Archaea Cell Wall
Lack cell wall or have walls made of pseudomurein (lacks NAM and D-amino acids)
Different Taxis
- Aerotaxis (oxygen)
- Phototaxis (photon intensity)
- Chemotaxis (chemical concentration)
-Positive if towards a stimulus and negative if away from a stimulus
Flagella Arrangements
- Peritrichous (all over cell)
- Monotrichous (one on one end)
- Lophotrichous (multiple on one end)
- Amphitrichous (one on each end)
Flagellar Motion
Move like a rotor; can be reversible or unidirectional
Flagellar Structure in Gram Negative
Filament of flagellin connects to hook which passes through the outer membrane via the L ring; the rod then passes through the peptidoglycan layer through the P ring and the plasma membrane through the MS ring, which terminates at the C ring; motor proteins surrounding the MS and C rings generate motion
Fimbriae and Pili
- Made of self-assembling flagellin-like proteins
- More numerous and shorter than flagella
- Fewer pili than fimbriae
- Pili are for gene transfer and surface attachment (twitching motility, i.e. dragging)
