prokaryotes functional structure

what is the purpose of the cell wall for bacteria in relation to osmosis

osmotic protection - prevents water moving to the area with high concentration of dissolved solute

what are the two types of bacteria

gram positive and gram negative

describe the process of gram staining

1. cells are smeared on a slide

2. cells are heated to fix onto the slide

3. crystal violet penetrates cells

4. iodine is used to stain cells purple

5. cells are decolourised with alcohol

6. if violet and iodine are taken up they will remain purple, if not the colour is lost

7. counterstain cells with safranin (pink)

8. makes cells with no colour visible

what colour do gram positive cells appear after gram staining

purple

what colour do gram negative cells appear after gram staining

pink

describe a gram positive cell wall

thick with a smooth surface

what two major structural components are found in gram positive cell walls

lipoteichoic and teichoic acid

what is the purpose of teichoic acid

• gives the cell a negative charge

  • bind to signalling molecules, e.g immune receptors

what is the purpose of lipoteichoic acid

creates integrity enabling the cell wall to anchor to the cell membrane

describe the structure of gram negative cell wall

a thin cell wall imbedded in the periplasm between two membranes

wrinkled surface

what is the primary component in the gram negative outer membrane

lipopolysaccharide

what are the 3 main structural components of lipopolysaccharide

lipid a

core polysaccharide

o polysaccharide

what is the jelly like layer surrounding a cell called

capsule

characteristics of the capsule

• usually several times larger than the cell, making overall cell size larger

• porous

• protective - prevents cell dehydration

what is the composition of bacteria’s cell wall

peptidoglycan

what do peptide cross bridges in peptidoglycan do

provide thickness and rigidity

what two polysaccharides forms peptidoglycan

NAM and NAG

what type of linkages are between NAM and NAG

beta 1,4

what is the purpose of the acetyl group in peptidoglycan

structural support

what forms between amino acids of different NAM molecules

cross links

what % of gram positive cell wall is peptidoglycan

90%

what percentage of gram negative cell wall iss peptidoglycan

10%

what is the main composition of archaea cell wall

pseudopeptidoglycan

what polysaccharies make up pseudopeptidoglycan?

NAT and NAG

what type of linkages are between NAG and NAT

beta 1,3

what causes variation in archaea cell wall

different habitats and environmental stresses

where are archaea commonly found

extreme environments

how could the cell wall be manipulated in order to kill a prokaryotic cell

• prevent production of enzymes forming peptidoglycan

• lysozymes to break the cell wall

• block peptide crosslinks

what structures are found on the exterior of prokaryotes

• fimbriae

• pili

• flagellum

what is a polar flagella

when they form at one end of the cell

what is peritrichous flagellum

when there is more than one around the cell

what is a lophotrichous flagella

one multiple are embedded at one end of the cell

how does flagella move

using motor (mot) proteins, enabling MS and c ring to interact which causes the whole ring to rotate and spiral

• like a whipping motion

what are pili

long thin tube structures that form when two bacteria become close together enable material to be shared - usually genetic information and antibiotic resistance

what is the fimbriae

small hair like structures that allow the cell to stick to a substrate

what are cell inclusions

energy reserves or stores of structural substances enclosed by a thin membrane. can be spherical or rod shaped

what does a bacteria chromosome contain

• essential genes densely packed

what does a plasmid contain

• non-essential genes

  • antiobiotic resistance and metabolic genes

what is a polylinker

a short sequence of DNA containing restriction enzyme recognition sites, contained in cloning vectors

describe the process of rolling circle replication

1. RepA binds at the ori and cuts one DNA strand, holding the 5’ end

2. DNA polymerase binds to exposed 3’ end

3. RepA recruits helicase to unwind the plasmid whilst DNA synthesis happens on the 3’ end

4. RepA joins the 5’ strand together then releases

5. DNA ligase seals the double stranded plasmid

6. RNA polymerase makes a primer on the 5’ strand which DNA polymerase uses as a strating point for synthesis

7. DNA ligases seals the new double stranded plasmid