2- prokaryotic cell structure and function Flashcards
cell theory
a unifying concept that states that cells are a fundamental unit of structure, function and organisation in all living organisms
cells
the basic functional unit of all living organisms
tissues
a group of similar cells
organs
a group of tissues
organ systems
a group of organs
ultrastructure of prokaryotic cells
- nucleotide
- plasmids
- 70s ribosomes
- cell wall
- slime capsule
- flagellum
- pili
- bacterial conjugation
- mesosomes
nucleotide
- singular circular piece of DNA
- not associated with proteins
- free in the cytoplasm
plasmids
- small loops of DNA
- contains genes that can be passed between bacteria
- replicates and moves through cells by the pili, even across species
- can reproduce independently of the nucleotide
70s ribosomes
- composed of a large 50s subunit and a small 30s subunit
- the site of protein synthesis
cell wall
- the cells rigid outer covering
- made out of peptidoglycan
- provides the cell with strength and support
- prevents the cell from bursting due to osmolysis
slime capsule
- a protective slimy layer which helps the cell retain moisture and adhere to surfaces
- protects from chemicals and phagocytosis
- covers antigens
flagellum
- a tail like structure which rotates to move the cell
pili
- hair-like structures which attach to other bacterial cells
- allows plasmids to move from cell to cell
bacterial conjugation
- a conjugation tube forms from the pili
- the donor plasmid replicates
- the plasmid moves through the conjugation tube and into the recipient host cell
- it forms a new plasmid
mesosomes
- infoldings of the inner membrane which contain enzymes required for respiration
label
draw gram positive bacteria
draw gram negative bacteria
gram positive bacteria
their cell wall consists of a thick peptidoglycan layer
gram negative bacteria
their cell wall consists of a thin peptidoglycan layer and an outer lipopolysaccharide layer
gram staining method
1) add water soluble crystal violet over a fixed culture. let it incubate. rinse with water
2) add iodine solution. let it incubate
3) rinse with alcohol. rinse with water
4) add with secondary stain, safranin. let it incubate. rinse with water
why do you add crystal violet during gram staining method
the crystal violet binds to the peptidoglycan cell wall
why do you add iodine during gram staining
this is a mordant that fixes the crystal violet to the cell wall by creating a larger molecule than the original crystal violet and iodine
why do you rinse with alcohol during gram staining
this decolourises gram negative bacteria, the outer lipopolysaccharide layer dissolves. the thinner peptidoglycan layer is unable to retain the complex, and the colour is lost
why do you rinse with water during gram staining
the large crystal violet iodine complex can’t penetrate the tightened and dehydrated peptidoglycan layer of gram positive bacteria and the colour is retained
why do you add a secondary stain during gram staining
if cells are gram negative, they lose the primary stain and look red
why rinse with water a second time during gram staining
if cells are gram positive, they retain the primary stain and look purple
effect of penicillin on gram positive bacteria
- penicillin binds irreversibly to the bacterial enzyme transpeptidase, inhibiting the formation of cross links in the peptidoglycan layer
- the cell wall is weakened
- when water moves into the cell, the cell will burst and die
effect of penicillin on gram negative bacteria
penicillin cannot penetrate the outer lipopolysaccharide layer
