Flashcards in Structural Macromolecules (Dr Alderwick): Part 1 Deck (30):
What is the most well studied prokaryote?
What is the primary role of the cytoplasmic membrane (CM)?
- separates the cytoplasm from the cells enviornment
- permeability barrier
Describe the composition of the CM
- phosphatidylethanoloamine ( fatty acids)
- arranged into phospholipid bilayer
- 6-8 nanometers wide
Describe the fluid mosaic model of the bacterial cytoplasm membrane
- contains a range of diverse membrane proteins
- enzymes ( PBPs- peptidoglycan biosynthesis )
- transporters (move molecules OUT--> IN or IN--->OUT)
- site of generation and us of the proton motive force
- 2-6 atm of osmotic trudger pressure = extremely fragile
Explain briefly the architecture of the Archeal CM
- lipid tails are attached to glycerol via an either linkage
- lipids are braced with methyl (CH3) groups- isoprenes
- Phytanyl (C20) or Biphytanyl (C40) <- glycerol on both ends
- crenarchaeol - hydrocarbon moiety contaiing 5 and 6 carbon rings
- glycerol dieters made from C20 phytanyl lipids forms a ?
- diglycerol tetra ethers made from C40 Biphytanyl lipids forms a?
- lipid monolayer
- both types of membranes are extremely resistant to ? Wide spread among?
- heat denaturation
Despite chemical variation in CM lipids between Archaea and Bacteria, the CM functions to ?
- form a membrane with inner and outer hydrophilic surfaces
- allows for PERMEABILITY which has its inherent problems
- anchor for membrane proteins and membrane associated proteins
- site of generating of proton motive force
What are the three major classes of transport systems for CM?
1. Simple transport
2. Group Translocation
3. ABC transporter
Explain simple transport
- driven by the energy in the proton motive force
Explain group translocation
- chemical modification of the transported substance driven by phosphoenolpyruvate
Explain ABC transporter
- periplasmic (outside) binding proteins are involved and energy comes from ATP
ABC = ATP Binding Cassette
With the bacterial cell wall: Peptidoglycan (aka murein) there are two major classes - what are they?
1. Gram-positive (ex: S. aureus)
2. Gram - negative (ex: E. coli)
Explain the study by hans christian gram for positive and negative !
- Gram + and Gram - were tested via fixation --> crystal violet--> iodine treatment--> decolorization --> counter stain safranin
** gram+ retained the initial violet colour throughout
**gram - the colour changed as the process went on...it changed colour after the decolourization process whereas the gram + retained it
The molecular structure of bacterial peptidoglycan:
- types of linkages?
- two components?
- beta (1,4) linkages between Glycan (made from carbohydrate)
- peptide component made from aas
Describe the Gram positive cell wall!
- no outer membrane - Gram -ve
- >90% cell wall is peptidoglycan
- forms glycol strands
- additional cell wall components
- Teichoic acids
- Wall associated protein ( ie. M-Antigen of Grp A Streptococci
Gram positive cell wall:
- Teichoic Acids?
-ve charged polyalcohols
- Ribitol phosphate
- glycerol phosphate
- other sugars
- Wall teichoic acids WTS
-lipoteicoic acids LTA
- bind Ca 2+ and Mg 2+
The gram negative cell wall
- describe it
- porin: water filled channel= entrance and exit of solutes specific and on specific
- contains lipopolysaccharide (LPS)
Gram negative: Explain the structure of LPS's Lipid A
- is it a glycerol lipid?
-fatty acids are linked via to a ?
-anchors the LPS to?
- not a glycerol lipid
- fatty acids are linked via an ester amide bond to a N-acetylglucosamine phosphate disaccharide
-Caproic (C6), lauric (C12), myrristic (C14), palmitic (C16) and stearic (C18) fatty acids
- anchors the LPS molecule into the outer leaflet of the outer membrane
Gram negative: Explain the structure of LPS's core polysaccharide
- contains ketodeoxyoctanate (KDO)
- C7 sugars (heptoses) - phosphorylated
- Glactose, glucose, rhamnose and mannose
- other more obscure sugars
L> tyvelose, paratose, colitose and abequose
Gram negative: Explain the structure of LPS's O-specific polysaccharide
- is it variable or not
- what is it referred to as
- full length is called?
- short length?
- sometimes referred to as the O-antigen
- extremely variable - species specific
L> >160 different O-antigens produced by different E. coli strains
- full length O antigens are deemed to be smooth LPS molecules -> outer membrane is less penetrable to hydrophobic antibodies
- short O-antigens derive rough LPS molecules --> outer membrane is more penetrable to hydrophobic antibodies
- since the O antigen is exposed to the surface it is recognized by antibodies
What are the three parts to the LPS structure?
1. Lipid A
2. Core polysaccharide
3. O-specific polysaccharide
Cell wall components of Archeae?
- similar to peptidoglycan
- N-acetylalosaminuronic acid
- beta (1, 3) glucosidic linkage
- all amino acids are of the L-stereoisomer
- lysozyme insensitive
Bacterial cell wall - how does the immune system keep the onslaught of a bacterial infection in check?
- first line of defence is lysozyme!
What did Sir Alexander Flemming discover?
- lysozyme is present in a number of secretions such as saliva, milk, mucus and tears
-part of the innate immune system
- natural protection from gram-positive pathogens.
- he treated bacterial cultures with nasal mucus from a pt suffering form a head cold
- whereas the skin is a protective barrier due to its dryness and acidity the conjunctiva (membrane covering the eye) is instead, protected by secret enzymes..mainly lysozymes...failure or disruption = conjunctivitis
Explain what N-acetylmuramide glycanhydrolase is
- a prominent cleft between the two domains forms a binding site
- recognizes and binds with a high affinity a hexasacharide of the glycol chain
- cleaves NAG-beta (1-4-NAM glycosidic bond
Flemming is also known for the discovery of penicillin.
- beta lactins
- four membered ring
- attacks an important enzyme involved in the synthesis of the bacterial cell wall
How does penicillin work?
- in bacterial cell wall an enzyme links NAG and NAM
- penicillin stops this joining
- cell has high internal osmotic pressure and it lyses under that force causing it to spill into the enviornment
**must be used on a penicillin strain strain