Oxidative Stress Flashcards
What is the problem with free radicals gaining electrons from other molecules?
This tends to result in the production of a second free radical which leads to proposed damage.
What is superoxide?
This is an oxygen molecule with an extra electron. It is a source of other Reactive oxygen species and initiates free radical production.
What is H2O2?
Hydrogen peroxide. This is not a reactive oxygen species, however it is highly reactive and leads to free radical formation. It breaks down into a hydroxyl radical and water.
What is peroxynitrite and how is it formed?
ONOO-. It is formed from a nitric oxide radical and a superoxide molecule. It is not a free radical but is a powerful oxidant and so can cause damage to cells.
State the two ways in which ROS can cause damage to DNA.
Damage to base - modified base leads to mis pairing and mutation.
Damage to sugar - causes strand to break, mutation on repair.
Explain how ROS can lead to protein degradation.
ROS can cause damage to the backbone of protein molecules causes them to form fragments. This then leads to protein degradation.
What happens when ROS react with protein side chains?
This can lead to a change in the folding of the protein. If this results in loss of function it will be degraded.
What can affect disulphide bonds in proteins?
ROS can take an e- from one of the residues then this can lead to misfolding, cross linking and functional disruption.
Explain what happens when an ROS interacts with a lipid.
Firstly it extracts a hydrogen atom from a polyunsaturated fatty acid. This then reacts with oxygen to for a lipidperoxyl radical. This then takes a hydrogen from a nearby fatty acid and a chain reaction begins.
What is the consequence of a ROS interacting with a lipid in a phospholipid bilayer?
This decreases membrane integrity because the homophobic environment of the bilayer will be interrupted and a fatty streak may form – atherosclerosis.
Give examples of exogenous biological oxidants.
Radiation, pollution, drugs and toxins.
Give examples of endogenous biological oxidants
From electron transport chain, nitric oxide synthases, NADPH oxidases.
Why is the electron transport chain at risk of producing biological oxidants.
Sometimes, electrons can escape from the chain and react with oxygen to give superoxide.
Why do we have nitrogen oxide in the body?
In phagocytes this has a direct toxic effect. It is also used as a signalling molecule.
What is respiratory burst?
Rapid release of superoxide and hydrogen peroxide by phagocytic cells to destroy invading bacteria.