Prokaryotic Outline Flashcards
Overview of Prokaryotic Cell Structure
Exist in a wide variety of sizes, shapes, and cellular aggregation patterns
Simpler structure than eukaryotic cells
Has unique structures not observed in eukaryotes
may occur as individuals, groups of 2 or more cells or chains, tetrads, clusters
may divide in 1 or more planes
circular
cocci
rod shaped cells
coccobacilli
vibrio
single or may form short chains
bacillus
curved rods -
vibrio
may be “coccoid” in shape (very short rods)
coccobacilli
rigid spiral shaped
Spirochetes
spirilla
– flexible helices
Spirochetes
network of long, multinucleate filaments
mycelia
other weird shapes
Squares, Star-shapes, Triangular
many shapes
pleomorphic
Prokaryotic cells may form ______ after cell division
groupings
Cells _______ _______ after cell division for characteristic arrangements
adhere together
Arrangement depends on
plane of division
Division along a single plane may result in pairs of cells or
diplococci
Example: Neisseria gonorrhoeae
Division along a single plane may result in chains of cells
streptococci
Example: species of Streptococcus
Division along two or three perpendicular planes form _____ or __________
tetrads;cubical packets
Division along several random planes form
clusters
Some bacteria live in groups with other bacterial cells; They form ________
multicellular associations
examples of multicellular associations
myxobacteria, cyanobacteria
what are the basic cell components
Cell wall Cell membrane Cytoplasmic matrix ribosomes inclusion bodies Nucleoid External features (at least for some bacteria)
Prokaryotic Cell Walls
- Rigid structure lying just outside the plasma membrane
- Mycoplasms and some Archaea lack cell walls
- Provides characteristic shape to cell
- Protects the cell from osmotic breakdown
gram staining reaction results from differences in
the cell wall structure
when and who developed the gram stain
Christian Gram (1884)
Bacterial Cell Walls
• Rigidity of cell wall is due to peptidoglycan
o Compound found only in Bacteria
• Composed of glycan chains of disaccharide.
o Disaccharide consists of N-acetylglucosamine (NAG) & N-acetylmuramic acid (NAM)
• Glycan chains held together by tetrapeptide chains
Tetrapeptide connections may contain
o D-isomers of amino acids
o Diaminopimelic acid (DAP)
Found no where else in nature
Connection may be
direct or through a peptide interbridge
gram positive cell wall
• Formed of a relatively thick layer of peptidoglycan
o As many as 30 sheets
o Despite the thickness, is permeable to numerous substances
• Teichoic acids
o polymers of glycerol or ribitol joined by phosphate groups
o Joined to peptidoglycan via NAM
o Stick out above peptidoglycan giving cell negative charge
Lipoteichoic acids bind to the plasma membrane
teichoic acids
gram negative cell wall
- Consist of a thin layer of peptidoglycan surrounded by an outer membrane
- Outer membrane composed of lipids, lipoproteins, and lipopolysaccharide (LPS)
- No teichoic acids
what is the periplasmic space
Gap between plasma membrane and cell wall (gram-positive bacteria) or between plasma membrane and outer membrane (gram-negative bacteria)
gel like substance that occupies periplasmic space
periplasm
o found in periplasm of gram-negative bacteria o some of their functions include nutrient acquisition electron transport peptidoglycan synthesis modification of toxic compounds
periplasmic enzymes
o secreted by gram-positive bacteria
o perform many of the same functions that periplasmic enzymes do for gram-negative bacteria
Exoenzymes
Lipopolysaccharides
• Consist of three parts
o O side chain (O antigen)
o Core polysaccharide
o Lipid A
gram negative cell wall outer membrane
lipopolysaccharide layer (LPS layer)
what is a lipid bilayer
outer leaflet made of lipopolysaccharides not phospholipids
outer membrane serves as
barrier to a large number of molecules
porin proteins
form channels through which small molecules (600-700 daltons) can pass
outer membrane is more permeable than plasma membrane due to
presence of porin proteins and transporter proteins
