10. Flashcards
(9 cards)
1
Q
porins
A
channels for movement of hydrophilic low-molecular-weight substances
2
Q
gram stain reaction
A
insoluble crystal violet-iodine (CV-1) complex forms inside cell
complex is extracted by alcohol from gram negative, not gram positive bacteria
3
Q
gram positive cell walls
A
-thick cell walls consisting mainly of peptidoglycan
-because dehydrated during alcohol step so pores in wall close
-prevents CV-1 complex from escaping
thats why we do not extract gram positive from alcohol
4
Q
gram negative bacteria cell wall
A
alcohol penetrates OM
- CV-1 extracted from cell
- cells appear nearly invisible until counterstained with second dye (safranin)
5
Q
archaeal cell walls
A
- no peptidoglycan
- no outer membrane
- pseudomuerin
- cell walls of some archaea lack pseudomurein
6
Q
pseudomurein
A
- polysaccharide similar to peptidoglycan
- composed of N-acetylglucosamine (G) and N-acetylalosaminuronic acid (T) (held with beta 1,3 bond)
- found in cell walls of certain methanogenic archaea
7
Q
archaeal cell walls : S layers
A
- most common cell wall type in archaea
- consist of protein or glycoprotein
- paracrystalline structure
- some archaea have only S-layer (no other cell wall components )
- most have addition cell wall elements
8
Q
summary of archaeal cell walls
A
- variety of structures possible
- some closely resemble peptidoglycan
- others lack polysaccharide completely
- most archaea contain some type of cell wall structure - functions to prevent osmotic lysis and give shape
- because they lack peptidoglycan, archaea are resistant to lysozyme and penicillin
9
Q
periplasm
A
space located b/w cytoplasmic and outer membranes
approx 15nm wide
contents have gel like consistency
houses many proteins
