Metabolism - ROS Flashcards
How is NO radical formed?
Formed from arginine by the enzyme nitric oxide synthase
Which drugs can form ROS?
1) . Antimalarials
2) . Paraguay (reactive herbicide)
3) . Paracetamol
How is ONOO- formed?
Reaction of O2 with NOradical
How is a OHradical formed?
Produced in all cells by ionising radiation.
How is the superoxide radical formed?
In the ETC, 0.1-2% of electrons escape and react with oxygen
How is O2- rid of?
It is converted to H2O2 by superoxide dismutase, which is then converted to H2O and O2 by catalase. Catalase is present in all cells.
How does glutathione protect cells against ROS?
It contains an SH group. This means it can donate a H to oxidised species = reducing agent.
Forms glutathione disulphide by forming a disulphide bind and reduces the oxidised species.
How does NADPH aid in defence against ROS?
It oxidises glutathione disulphide back into glutathione using GSH reductase and GSH peroxidase.
What is oxidative burst and its purpose?
NADPH oxidase causes the cells to release superoxides and H2O2 from themselves rapidly to kill bacteria.
What is lipid peroxidation and why is it an issue?
We’re unsaturated lipids react with ROS to form lipid peroxides.
These damage cell membranes and continue to react in a chain reaction.
Oxidised lipids can also build up in the intima of arteries = plaque formation.
What conditions are ROS linked to?
Cancer
Pancreatitis
Type I diabetes
Alzheimer’s
What happens in G6P dehydrogenase deficiency?
G6P dehydrogenase is missing = no NADPH produced by pentose phosphate pathway.
This means once all glutathione has been used up in reducing OHradicals, they cannot be recycled and remain as glutathione disulphide.
As a result, the OHradicals can attack membranes of cells (cell lysis) and ROS can attack haem groups in RBCs = denature the proteins and form Heinz bodies.
How are proteins affected by ROS?
When attacked by ROS, those that contain Cys residues will form disulphide bonds, denaturing them.
What are antioxidants?
Flavonoids
VitC, A, E
Zinc and selenium
List the ROS.
O2- ONOO- OHradical NOradical H2O2
