BMS314 Lecture 23: Week 11 Lecture 23 - Free radicals and Cell Death
• The molecule is most stable when it has paired electrons
o Unpaired electrons means its unstable and more reactive
• When you have a free radical, all the molecules surrounding it are at risk of having to donate
an electron and in the process become oxidised to try stabilise this highly reactive molecule
• Occurs very quickly, danger comes when
o there is a lot of them
o The balance between the free radicles and the mechanism to control the free radicles is
compromised (favouring the free radicles)
• Can result to tissue and organ failure (clinical disease)
• Cells use free radicles in normal cell metabolic processes
• Exogenous -> exposure from our environment
• ROS
o Macrophages
o Neutrophils
• RNS
o Nitric oxide in relation to inflammation and vasodilation
• Drugs
o Chemicals that regularly cause cell injury due to them containing free radicles
• Progression of donating and loosing electrons and thus the generating of free radicles to
produce reactive oxygen species
• If molecules oxygen is reduced (receives and electron), it becomes superoxide anion
o In the presence of hydrogen ions this can then become hydrogen peroxide
• Hydrogen peroxide itself is an oxidant which can break down and form hydroxyl radicles
o In the presence of more hydrogen ions it can then become water
• This is a dynamic which is occurring within the Extracellular space, also within cells themselves
(lysosomes)
o Generating free radicles either for good or for bad (cell injury)
• Need oxygen to survive however it can be dangerous and produce free radicals
• Normally free radical formation
o Cellular respiration
o Electron transport system
o Oxidative phosphorylation
• All of this is occurring in the mitochondria
• If the mitochondria become damage this can be a problem in the generation of free radicals
• How do free radicals kill bacteria?
o They attack the critical cell functions (4 of them)
o Generally the free radicals damage the cell membrane to get inside the cell, causing
nucleic acid injury and preventing protein synthesis
