Module 4: Microbiology Flashcards
Microbes make up ____ the biomass on Earth
half
Where is the chromosome of a prokaryotic cell found
Nucleoid
What is the order of layers of a prokaryotic cell (inside to out)
Plasma membrane, cell wall, glycocalyx
What shapes can bacteria be
Cocci, rods, spirals
What is the function of a prokaryotic cell membrane
Cell regulation
What is the function of a prokaryotic cell wall
Cell integrity, shape, strength, prevent desiccation, osmotic lysis
What is the purpose of the glycocalyx
Extracellular: cell protection
Do archaea have peptidoglycan cell walls
No
Describe the bacterial genome and its location
One circular chromosome restricted to an area known as the nucleoid, and plasmids in the cytosol
What are plasmids
Small circular self replicating DNA molecules found in the cytosol
What are prokaryotes that lack cell walls called
Mycoplasmas (group of pathogenic bacteria)
Describe the structure of peptidoglycan
NAM-NAG sugar chains cross linked laterally by amino acid chains and vertically by amino acid side chains
What is the enzyme that cross links NAM-NAG sugar chains and amino acid chains
Transpeptidase
What are the most common gram stain reference bacteria
Staphylococcus aureus (gram positive) and escherichia coli (gram negative)
What colour are gram positive bacteria stained
Purple
What colour are gram negative bacteria stained
Red/pink
What are the four steps of the gram stain procedure
Application of crystal violet (purple dye), application of iodine (mordant), alcohol wash (decolourisation), application of safranin (counterstain)
Describe the structure of a gram positive bacterial cell wall
Thick peptidoglycan layer makes up the cell wall, plasma membrane underneath
Why do gram positive bacterial cells retain the crystal violet
Peptidoglycan traps violet, masks red
How thick is the peptidoglycan layer of gram positive bacteria
THICK: 20-80 nm
Describe the structure of a gram negative bacterial cell wall
Thin peptidoglycan layer and outer membrane make up the cell wall, plasma membrane underneath
Why do gram negative bacterial cells not retain the crystal violet
It is easily rinsed away, revealing red safranin dye
How thick is the peptidoglycan layer of gram negative bacteria
THIN: 5-10 nm (between two plasma membranes)
What does the gram negative bacterial outer membrane have that gram positive doesn’t
Carbohydrate portion: lipopolysaccharide