Lecture Set 1 : Part 4 Flashcards
what are the most common cell morphologies for cell shape?
-coccus (cocci)
-bacillus (bacilli)
-spirillum (spirilla)
what is a coccus shape? what is an example of a bacteria with this shape?
-roughly spherical
-ex: streptococcus pyogenes
what is a bacillus shape? what is an example of a bacteria with this shape?
-rod shaped
-ex: E. coli
what is a spirillum shape? what is an example of a bacteria with this shape?
-spiral shaped
-ex: spirillum volutans
what are some uncommon cell shapes?
-spirochete (cork screw)
-budding and appendaged bacteria (stalks/hyphae)
-filamentous bacteria (thread like)
what is an example of a bacteria with a spirochete cell shape?
-treponema pallidum
what is an example of a budding and appendaged bacteria?
-caulobacter crescentus
what is an example of a filamentous bacteria?
-streptomyces griseus
what can result from budding and appendaged bacteria?
-asymmetrical cell shapes because of asymmetrical cell division
what is the purpose of stalks and hyphae?
-increase SA
what happens to the cells of some prokaryotes?
-cells remain together after cell division and form characteristic arrangements
what are examples of some of the characteristic arrangements of prokaryotes?
-members of genus staphylococcus form grape-like clusters
-some cyanobacteria form long chains (ex: anabaena)
-many coccoid bacteria form tetrads (ex: micrococcus and deinococcus)
what does morphology not predict of a prokaryotic cell?
-physiology, ecology, and phylogeny
-morphology is genetically encoded
what are the possible selective forces in setting cell morphology?
-optimization for nutrient uptake (for small cells and cells with high SA/V)
-swimming motility (helical or spiral shaped cells)
-gliding motility (filamentous bacteria)
what are the ranges for eukaryotic and prokaryotic cell size?
-eukaryotes (10-200 micrometers in diameter)
-prokaryotes (0.2-700 micrometers)
-despite overlap, prokaryotes are very small compared to eukaryotes
how is cell size influenced by cell structure?
-eukaryotic cells can actively transport molecules within the cytoplasm (can be larger)
-prokaryotic cells must rely on diffusion for transport (limits size, must stay small)
why must prokaryotes stay small in order for diffusion to be effective?
-diffusion is fast at small distances but the rate of diffusion increases quickly with each additional unit of distance
-increases by the square of the distance (distance = 2m, rate = 2^2)
what are examples of average sized prokaryotes?
-E. coli (1.0 x 3.0 micrometers) (bacillus cell shape)
-staphylococcus aureus (1.0 micrometer diameter) (coccus cell shape)
what is an example of a very small prokaryote?
-mycoplasma genitalium (0.3 micrometers)
what is an example of a very large prokaryote?
-epulopiscium fishelsonii (80 x 600 micrometers)
what is an advantage of small cells? what does this control?
-higher SA/V
-controls its growth rate (cell’s ability to exchange with the environment)
what are the advantages of having a high SA/V?
-greater nutrient exchange per unit of cell volume
-allows for faster growth (b/c of exchange)
-high population #s (b/c of faster growth)
-increased rate of evolutionary change (b/c they can divide faster = more likely for mutations to happen)
what limits having a smaller cell?
-need to fit organelles
-cell cannot function without these
-cells less than 0.15micrometers in diameter are unlikely
what environment contains many smaller cells? why is it important to have small cells here?
-oceans (cells that are 0.2-0.4 micrometers in diameter)
-less nutrients in the ocean so they need better exchange
