Free radicals Flashcards
define free radical
any species (atom or molecule) that is capable of independent existence and contains one or more unpaired electrons.
what are the consequences of radicals targeting DNA?
apoptosis or necrosis
what are the consequences of radicals targeting DNA?
apoptosis or necrosis
where do free radicals come from?
they’re derived from either normal metabolic processes in the human body or from external sources.
what external/environmental sources produce free radicals?
UV light, smoking, air pollution, ionising raditation.
what kind of radiation has high tissue penetration?
x-rays and gamma rays
how does ionising radiation cause damage in the cells?
free radicals can split water in the cells into hydrogen and hydroxyl radicals.
which cells are susceptible to ionising radiation?
gastrointestinal cells, fetal cells, bone marrow cells and lymph nodes
name O2*−
superoxide
how is O2*− super oxide produced?
40% leakage of electrons from electron transport chain
name H2O2
hydrogen peroxide
how is H2O2 hydrogen peroxide produced?
not a radical - but it liberates OH
name RO*
organic radical
name OH*
hydroxyl radical
how is RO* produced?
produced from attack of C=C bonds
how is OH* produced?
generated from H2O2 from Fenton reaction
name RCOO*
peroxyl radical
how is RCOO* produced?
generated from lipid attack
name HOCL
hypochlorus acid
how is HOCL produced?
respiratory burst
what cellular structure is most likely to be exposed to the hydroxyl radical?
mitochondria
what is nitrosative stress?
refers to the joint biochemical reactions of NO and O2*− when an oxygen metabolism disorder occurs in the body.
name some of the effects of ROS on cellular structures.
damaged membrane - increased permeability, damaged mitochondria - reduced ATP production, DNA damage - mutations, protein misfolding.
why are membranes and lipids susceptible to damage from ROS?
they are polyunsaturated fatty acids
3 stages of a radical chain reaction
initiation, propagation, termination
what is lipid peroxidation?
a process under which free radicals attack lipids containing carbon-carbon double bonds.
what does lipid peroxidation cause?
decrease in membrane fluidity, damage to membrane proteins (receptors and their function!!), increase in “leakiness” to K+ and Ca2+.
what is produced when a radical attacks guanine in DNA?
8-OHdG , deoxyguanosine. It is mutagenic and the biomarker of carcinogenesis.
what happens when a radical attacks guanine in DNA?
Impaired protein synthesis. This base pair trans version of guanine is notable in some forms of cancer.
what are the 3 stages of cellular change/adaptation?
proliferation, apoptosis, necrosis
what does ROS-DNA damage cause?
strand breakage, purine, pyrimidine, or deoxyribose modifications in base pairs and cross-linkage.
what can DNA damage lead to?
replication errors, induction of transcription.
how do radicals initiate atherosclerosis?
damage blood vessel walls
