PGL synthesis+ Transport

Question 1

Peptidoglycan

Answer 1

Large polymer that forms a mesh-like scaffold around the bacterial cytoplasmic membrane
Cable-like structure
two principal components:
Glycan strands of repeating disaccharide units
Peptide chains of 2 to 5-amino acid residues

Question 2

Peptidoglycan structure

Answer 2

Alternating repeats of Nam +Nag
NAM-N-acetylmuramic acid
NAG-N-acetylglucosamine
Amino Acids: L-alanine,D-alanine, D-glutamic acid, Diaminopimelic acid (DAP)

Question 3

PGL Polymer

Answer 3

Strands of PGL form a sheet surrounding the cell
Connected by peptide cross-links-vertical
Dap forms cross-links with other peptide chains
B-1,4-glycosidic bonds
between Nag+Nam-horizontal

Question 4

Variation

Answer 4

+cross links contain short peptide interbridge
- cross-links form DAP of one glycan strand to d-alanine on the adjacent strand

Question 5

Synthesis

Answer 5

Important for cell elongation
three stages
Precursor formation: within cell, nag +Nam,occurs in the cytoplasm,polymerization:form functional PGL strand
Cross-linking

Question 6

1st step

Answer 6

Autolysins break B-(1,4)-glycosidic bonds
cuts PGL strands-breaks bond

Question 7

2nd step

Answer 7

NAG-undecaprenyl phosphate formed in cytoplasm
Activated monosaccharide-sugar with UDP

Question 8

3rd step

Answer 8

NAM-pentapeptide-UDP formed in cytoplasm
also known as park’s nucleotide

Question 9

4th step

Answer 9

Bactoprenol-P picks up P-NAM-5aa,becoming Lipid l
UDP adds NAG, forming Lipid ll,bactoprenol+ PGL monomer

Question 10

5th step

Answer 10

Bactoprenol ferries PGL monomer across membrane, to periplasmic space, catalyzed by flippase

Question 11

6th step

Answer 11

NAM-NAG subunit brought in by bactoprenol, which is recycled.

Question 12

7th step

Answer 12

Glycosyltransferases form B-(1,4)- glycosidic bonds

Question 13

8th step

Answer 13

Transpeptidases form peptide cross-links

Question 14

Transport

Answer 14

In two groups
Passive: Move things with the gradient=diffusion
Active: Against the concentration gradient-Energy

Question 15

Simple Diffusion

Answer 15

Passive movement of molecules or ions across a membrane
without a helper protein

Question 16

Facilitated Diffusion

Answer 16

It is the same as simple diffusion but with transport protein in the membrane

Question 17

Primary active transport

Answer 17

Requires energy-against gradient
most common is ATP
Very specific
specific transporters=specific molecules or ions

Question 18

Simple transport

Answer 18

Membrane-spanning transport protein
Powered by proton motive force
transfer of H+ through proton pump
through ATP synthase drives ADP to ATP

Question 19

Group translocation

Answer 19

power=Phosphor enol pyruvate
import sugars-Phosphorylates sugars as they come in
PEP to a sugar molecule

Question 20

ATP-binding cassette transporter (ABC)

Answer 20

High substrate affinity
power= ATP
Variety of compounds-pump out antibiotics +toxins
Solute-binding protein: G+ out, G- periplasmic space.

Question 21

Secondary active transport

Answer 21

Co-transport
The energy created by primary active transport to transport other molecules against their concentration gradients

Question 22

Symport

Answer 22

Molecules move in the same direction
High to Low
uses energy from primary

Question 23

Antiport

Answer 23

Molecules move in the opposite direction
one in, one out