the outer membrane of gram-negative                                 bacteria serves as an extra barrier which:
 *resists certain antimicrobial chemicals
 *makes it harder to inhibit or kill than gram + bacteria

Bacterial cells walls are made from
peptidoglycan.
Peptidoglycan isnt found anywhere else on Earth.

why don't all cells have the same structure?

let's examine the structure of prokaryotic cells from the outside in...

peptidoglycan is a polysaccharide made from two cousins of glucose
N-acetylglucosamine (NAG) and
 N-acetylmuramic acid (NAM).
These sugars are arranged in alternating long chains cross-linked
in a lattice-like structure.

eukaryotic vs prokaryotic cells

Bacteria are divided into two major groups: 
Gram positive and Gram negative
(based on their reaction to Gram staining, an identifying technique named after Danish scientist Hans Gram 1853–1938).








​

Gram +  vs  Gram - 
bacterial responses to the staining procedure are due difference in their cell wall structure. 

Biofilms are communities of microbes stuck together and adhered to a surface encased in a slimy layer.

cell structure matches cell function.
​a muscle cell has a very different structure AND function ​vs a nerve cell.
a plant cell differs significantly from a bacterial cell.  

Gram staining allows us to classify bacterial cells based on cell wall structure

 Alcohol dissolves lipids in the outer membrane damaging the cell so
alcohol swabs can be used to cleanse the skin clinically

Cell Function: 
​Diffusion and Osmosis

                The exterior of Bacteria is different from                            that of the Archaeans and Eukaryotes.
 Cell walls function as a structural, protective layer     Some bacteria also have:
    1. A polysaccharide capsule found outside the cell
        wall which:
        *helps the cell attach to surfaces, 
        *protects the cell from dehydration,
​        *protects the cell from toxins
        *helps prevent the cell from being attacked
                 by phagocytes thereby helping bacterial
                 pathogens resist our immune system.
    2. Flagella which is used for locomotion
    3. Pili (pilus/fimbriae) used to attach to surfaces
    4. Plasmids which are ciruclar strands of DNA                           separate from the singular chromosome
    5. Endospores which can resist environmental
                 extremes

​Prokaryotic and eukaryotic cells differ significantly in structure,
             however, all cells have four common structures:
 1.a plasma membrane
 2. cytoplasm
 3. nucleic acids
 4. ribosomes

one glycerol

two fatty acids

one phosphate group

but the treatment of infections caused by gram-negative bacteria
requires drugs that can cross the outer membrane

solution =
solute + solvent

gram +

----------------------------------------------------------------------

end of cell structure/function

capsule        slime layer      biofilm

more about the cell wall

 Cells may also exhibit a 
    slime layer
 similar to a capsule but
loosely associated to the cell surface so easily washed away. A capsule and slime layer together are called a glycocalyx.

gram -

there are two primary categories of cells:
prokaryotic and eukaryotic

 the cell membrane

gram + cell walls also contain 
teichoic and lipoteichoic acids
​embedded within the peptidoglycan layers
adds strength to the cell wall and contributes to an acidic charge on the cell surface.