Prokaryotic Cells Flashcards
What are prokaryotic cells?
Rod shaped bacterium living cell that makes proteins and replicates DNA
Consists of: fimbrae, nucleoside, plasma membrane, cell wall, glycocalx, flagella and ribosomes
What is the bacterial genome?
Typically a single circular chromosome
No nuclear membrane, however the chromosome is restricted to defined region of the bacterial cell known as the nucleiod
Other small circular self replicating DNA molecules found in cytosol are plasmids
What is the function of Peptidoglycan?
Rigid macro molecular layer that provides strength to cell
Consists of different layers stuck together which increase strength
Protects cells from osmotic lysis and confers cell shape
What is Transpeptidase?
Enzyme that cross-links the peptidogylcan chains to form rigid cell walls
If not cross linked the cell will be weak and will die
What is a Positive Gram Stain?
A gram stain of mixed Staphylcoccus aureus
Purple
What is a negative gram stain?
A gram stain of Escherichia Coli
Red
What is the gram stain procedure?
Application of crystal violet dye
Application of iodine
Alcohol wash
Application of safranin - counterstain
Structure of gram positive bacterial cell wall
Stain a darker colour and have a thick cell wall of peptidoglycan
Responsible for differences in gram stain reaction
Structure of Gram negative bacterial cell wall
Have a thin layer of peptidogylcan between plasma and outer membranes
What is the function of bacterial flagella?
Some bacteria are capable of movement in liquid medium
Motile bacteria produce flagella
Long flexible appendage resembling tails, 10-20nm in diameter, 5-10 per cell
What is chemotaxis?
Bacteria move along a concentration gradient towards a chemical attractant (positive) or away from a chemical repellent (negative)
What is fimbriae?
Structures with adhesive properties that cause bacteria to stick/adhere to surfaces
Not involved in motility, not all bacteria possess fimbriae (inherited trait), much shorter and more numerous than flagella
What is pili?
Attachment to other bacteria
Transfer of genetic material from one cell to another
The genetic transfer is called conjugation
Conjugation is a form of horizontal gene transfer
What is the glycocalyx?
A gelatinous polysaccharide and/or polypeptide outer covering that forms a sticky mesh work of fibres
Capsule : glycocalx organised into defined structure attached firmly
Slime Layer : glycocalx disorganised without cell shape attached loosely
What are virulence factors?
Protect bacteria from phagocytosis and engulfment by immune cells Prevent cell from drying out/desicating
