Where is LPS located?
Outer membrane of Gram-negative bacteria
Where is LPS synthesised?
Inner membrane, then transported to the outer membrane
What are the three main roles of LPS?
Structure, barrier function, and protection
How does LPS contribute to structure?
Provides rigidity and increases negative surface charge
How does LPS act as a barrier?
Impermeable to large hydrophilic molecules and slows diffusion of small hydrophobic molecules
How does LPS protect bacteria?
Adds an additional protective outer layer for harsh environments
Which receptor recognises LPS?
TLR4
Which cytokines are induced by LPS?
TNF-α and IL-1β
Why is lipid A clinically important?
It is the main causative agent of endotoxic shock
What are consequences of systemic LPS exposure?
Hypotension, heart damage, endothelial injury, lung damage, DIC, organ failure, death
Why is LPS dangerous during infection?
Causes excessive inflammation that can lead to death
What are the three components of LPS?
Lipid A, core oligosaccharide, O-antigen
What is lipid A?
Hydrophobic anchor and most conserved endotoxin component
What part of LPS is most conserved?
Lipid A
What is the oligosaccharide core?
Inner conserved region and outer variable region
What is the O-antigen?
Repeating sugar units (4–40 repeats)
Which part of LPS is most variable?
O-antigen
Why is LPS synthesised at the inner membrane?
Outer membrane lacks energy for synthesis
Why is controlled insertion important?
Maintains outer membrane integrity
Where does lipid A synthesis occur?
Cytoplasmic face of inner membrane
Which proteins are involved?
Lpx proteins
What is unique about LpxA?
Hydrocarbon ruler selects 14-carbon acyl chains
Which proteins build the core oligosaccharide?
Waa proteins
What is rough LPS?
LPS without O-antigen
