Free Radicals 1 Flashcards
What is a free radical
Any species with one or more unpaired electron in the outer orbit
What elements are classed as free radicals
Hydrogen
Oxygen
Transition metals
Why are free radicals important in the body
Can damage -
Nucleic acids
Nucleotides
Covalent bonds
Lipids
Membranes
Give 3 methods that produce free radicals
Leakage from electron transport chains - Oxygen
Generated by activated phagocytes
Exogenous (external) sources of free radicals
Give some exogenous (external) sources of free radicals
ozone
cigarette smoke
radiation
pollutants
drug administration
diet
How can oxygen become a free radical
Oxygens pair up as covalent bonds as each O2 has 2 unpaired electrons.
The harmful effects of oxygen occur when
it is diverted from the stable O2 form to an
active state such as singlet oxygen (1 O2) and the free radical state superoxide (O-2)
What nitrogen species is a free radical
Nitric oxide
What electron transport chain components produce oxygen free radicals
1 and 3
What percentage of oxygens leak from electron transport chains in the mitochondria
1-3% but some data suggests as low as 0.15%
The higher the activity/energy expenditure - the more free radicals as more active electron transport chain
Give some cellular sites for the production of superoxide free radicals in muscle fibres
Sarcomeric proteins
Xanthine oxidase
Mitochondria - complexes 1 and 3 of electron transport chain
NADPH oxidases at the sarcolemma, sarcoplasmic reticulum and transverse tubules
What is the Fenton reaction
The Fenton reaction describes the formation of hydroxide (OH−) and hydroxyl radical by a reaction between Iron (or any free metal e.g. copper) and hydrogen peroxide
Free metal acts as a catalyst
Give 2 ways that free radicals are measured
Some indirect indicators of free radical production in vitro. (products of lipid peroxidation e.g ethane or DNA breaks caused by oxidation produce protein carbonyls)
The measure of antioxidant levels - particularly endogenous antioxidants.
Why is the Fenton reaction important
Superoxide carries out the Fenton reaction. This reaction produces hydroxide (OH-) which is a very reactive free radical compared to superoxide.
This hydroxyl radical is believed to contribute oxidative damage to living cells
Usually use both to get the full picture
Are all free radicals bad
No, have some important cell signalling roles
Why are free radicals hard to measure
Very short half-life