Cell Walls

Question 1

describe gram + bacteria

Answer 1

thick peptidoglycan (ppg)
plasma membrane beneath ppg
very small periplasmic space (pps)
very few periplasmic enzymes, more exoenzymes instead

Question 2

describe gram - bacteria

Answer 2

thin peptidoglycan (ppg)
plasma membrane beneath ppg
large periplasmic space (pps)
lots of periplasmic enzymes
outer membrane superficial to ppg layer

Question 3

most abundant phospholipid in bacteria cell membrane

Answer 3

phosphatidylethanolamine

Question 4

hopanoids

Answer 4

interspersed throughout the bilayer, serve to stabilize the membrane (similar to steroids found in eukaryotes)

Question 5

proteins and glycoproteins in the cell membrane

Answer 5

peripheral proteins
integral proteins (most abundant)
glycoproteins (oligosaccharides covalently attached to membrane)

Question 6

functions of membrane proteins

Answer 6

nutrient and waste transport in/out of the cell
transport of secreted proteins/toxins
carry out metabolic processes
interactions with environment (chemotaxis - moving towards food and away from toxins)
flagellar motors

Question 7

what does the envelope look like in gram + vs. gram - bacteria?

Answer 7

gram +: just ppg layer
gram -: ppg layer and outer membrane

Question 8

about peptidoglycan

Answer 8

contains peptides and sugars, found in most bacteria except mycoplasma species and archaebacteria (which have pseudo ppg)

Question 9

what kind of environment do most bacteria live in?

Answer 9

hypotonic - meaning the environment has less solute than the bacteria, so water rushes into the bacteria. the cell wall keeps the cell from bursting when this happens

Question 10

describe the outer membrane

Answer 10

found in gram - cells, has porin proteins that allow small molecules to pass
- holds in periplasmic enzymes
- helps avoid immune defenses
- barrier to toxic substances
- contains lps

Question 11

describe lps

Answer 11

• lipopolysaccharide
• found only in outer membrane of gram - bacteria
• very toxic, released when cell dies
  3 components:
• lipid A: embedded in bilayer
• core polysaccharide: about 10 unusual sugars between the lipid A and O antigen
• O antigen: extends out from core polysaccharide

Question 12

braun’s lipoprotein

Answer 12

embedded in outer layer of gram - bacteria, tethers outer membrane to thin ppg