Bacteria Chapter 2: Cell Structure Flashcards
What is the Svedburg unit (S)?
relates to density of molecules and how fast they sediment (during centrifugation)
What are bacterial ribosomes composed of?
is a 70S ribosome formed by:
large subunit: 50S
small subunit: 30S
What are eukaryotic ribosomes composed of?
is a 80S ribosome formed by:
large subunit: 60S
small subunit: 40S
Why do antibiotics targeting bacterial ribosomes not affect eukaryotic ribosomes?
bacterial 30S small subunit has 16S rRNA
eukaryotic 40S small subunit has 18S rRNA
What colour do gram-positive cells stain?
purple
What colour do gram-negative cells stain?
pink
What does the cell wall of Gram-positive bacteria consist of?
thick peptidoglycan
What does the cell wall of Gram-negative bacteria consist of?
- thin peptidoglycan
- outer membrane
What is peptidoglycan composed of?
- glycan chains
- cross-linking peptides
What are glycan chains composed of?
two joined sugars
- N-acetylglucosamine (NAG or G)
- N-acetylmuramic acid (NAM or M)
How does the outer membrane (OM) of Gram-negative bacteria differ from cytoplasmic membrane?
has lipopolysaccharide (LPS) – negatively charged
What do Gram-positive cell walls have that Gram-negative cell doesn’t?
teichoic acids (sugars)
- if anchored to PG: techoic acid
- if anchored to lipid in cytoplasmic membrane: lipoteichoic acid (LTA)
How are polysaccharide capsules anchored to the cell wall in Gram-negative bacteria?
via phospholipid
OR
replacing polysaccharide portion of LPS
How are polysaccharide capsules anchored to the cell wall in Gram-positive bacteria?
via NAM and NAG sugars (of peptidoglycan glycan chains)
What are the functions of capsules in bacteria?
- protect from being engulfed by phagocytic cells
- protect from phages trying to reach cell wall to infect celll
- mediate attachment to surfaces (ie. to get food)
- mechanism for specific attachment of pathogenic and non-pathogenic bacteria to surfaces (ie. prevent being swept out of body, off rocks, and be more resistant to predation, etc.)
What is a phage?
virus that infects bacteria
Where can pili be anchored?
cell envelope
- cytoplasmic membrane
- cell wall
What are the functions of pili?
- attachment to surfaces
- twitching motility
What is a serovar or serotype?
strain differentiated by immunological means
What does a bacterial cell wall consist of?
- plasma membrane
- cell wall
What are capsules?
outer layer produced by some prokaryotic cells
In prokaryotic cells like bacteria, transcription and translation are linked. Why is that?
DNA is not surrounded by a membrane, and mRNA does not need to be transported
out to cytosol
therefore, ribosomes can access mRNA as it is still being synthesized
What can antibiotics target?
- ribosomes
- RNA polymerase
- dNA polymerase
What structures are only found in some bacteria?
- flagella
- pili
- fimbriae
- capsule
