Oxygen Toxicity Flashcards
______ is probably the most potent ROS
Hydroxy radical
When O2 accepts single electrons, it is transformed into highly reactive ________ that demage cellular lipids, proteins and DNA
Oxygen radicals
One oxygen molecule can accept up to ______ electrons, generating __________
4
Superoxide, hydrogen peroxide
Hydroxyl radical, water
Hydrogen peroxide is not a radical but a ______ because it can generate hydroxyl radical
ROS
Transition metals, such as Fe2+ or Cu+, catalyze formation of the _______ from _____ in he non-enzymatic Fenton reaction
hydroxyl radicals
hydrogen peroxide
under physiological conditions, ____ are sequestered to reduce Fenton reaction. However, _____ can expose such metals to allow secondary free radical injury
transition metals
Injury
RNOS contain both nitrogen and oxygen and derive principally from the free radical ________
Nitric oxide (NO)
Free radical nitric oxide is produced endogenously by enzyme _______
Nitric oxide synthase (NOS)
One of the major sites of superoxide generation is ________ in the mitochondria electron transport chain
Coenzyme Q (CoQ)
The _______ form of CoQ can accidentally transfer an electron to dissolved O2, thereby forming _______
One-electron reduced
Superoxide
Name 3 enzyme in the cell that bind O2 and transfer single electron to it via a metal
Oxidase
Peroxidase
Oxygenase
_______ enzymes are a major source of free radical leakage
Cytochrome P450
Induction of cytochrome P450 enzyme by ____, ____ or ____ leads to increased cellular injury
Alcohol
Drug
Chemical toxicant
_____ and _____ are generated enzymatically as major reaction products by several oxidase present in peroxisome
Hydrogen peroxide
Lipid peroxide
Peroxisomal ________ generates hydrogen peroxide
Fatty acyl-CoA oxidase
Lipid peroxidase are formed enzymatically as intermediate in the pathway of many ______, including leukotrienes and prostaglandin
Eicosanoids
Ionizing radiation has a high energy level that it can split water into ___ and ____.
Hydroxyl
Hydrogen radical
Ionizing radiation can generate organic radical through direct collision with ______
Organic cellular component
______ that form lipid peroxyl radical and lipid peroxide make a major contribution to ____ -induced injury
Chain reaction
ROS
Initiator free radical, such as _______, begins chain reaction by extract a hydrogen atom from the double bond of _______ in membrane lipids
Hydroxyl radical
Polyunsaturated fatty acid
After extraction of hydrogen atom from fatty acid, the chain reaction is propagated when ______ adds to form _____ and _____.
O2
Lipid peroxyl radial
Lipid peroxide
Disruption of membrane integrity of membrane attack may result in further ______
Free radical production
_____ of lipid molecules can cause lipid degradation
Peroxidation
_____ formed from lipid peroxidation can _____ proteins
Aldehyde
Cross-link
As a result of oxidative damage, protein may cause _______, _____ and ______
Fragmentation
Crosslinking
Aggregation
Oxidation of cysteine sulfhydryl group of _______ compromise the cellular defense against free radical injury.
Glutathione
Oxygen derived free radical can cause ______ in DNA and also cause ______ backbone breakage
Base alteration
Deoxyribose
Nitric Oxide (NO) has a single electron and hence is ______
Free radical
At a low concentration, NO function as a ______ and as a hormone causing ______
Neurotransmitter
Vasodilation
At high concentration, NO combines with _____ or with _____ to form RNOS
O2 superoxide
RNOS is involved in neurodegenerative disease such as _______ and in chronic inflammation such as _____
Parkinson’s disease
Rheumatoid arthritis
NO is synthesized by the enzyme _______ from argnine
NO synthase
NOS has 3 tissue specific Isoform
Neuronal
Endothelial
Inducible
Neuronal and endothelial NOS are tightly regulated by ____ concentration and generate NO that serve as _____ or ______
Calcium
Neurotransmitter
Hormone
Inducible NOS are present in many cells of the immune system and can be induced to high level of expression and generate ______
RNOS
NO exert direct toxicity by attack ______ of ETC and Fe-heme protein such as Hb and cytochromes
Fe-S center
Under physiological condition, the effect caused by direct NO toxicity is low due to low abundance of ____
NO
Direct NO toxicity can cause serious damage in individual with _____ or ischemia
Oxidative phosphorylation disease
Superoxide dismutase converts _____ to _______
Superoxide
Hydrogen peroxide
In response to infectious agents and other stimuli, phagocytic cells of the immune system exhibit a rapid consumption of O2, in a process called _______
Respiratory burst
Respiratory burst is a major source of _______ (5 )
Superoxide Hydrogen peroxide Hydroxyl radical HOCl RNOS
Generation of free radical during _______ is intended to destroy invading microorganism or tumor cell.
Respiratory
The respiratory burst results from the activity of _______, which catalyze the transfer of an electron from NADPH to O2 to form ______
NADPH oxidase
Superoxide
Myeloperoxidase converts ______ to _______
H2O2
HOCl
formation of hypochlorous acid from hydrogen peroxide is catalyzes by ________, a heme containing enzyme that is present only in phagocytic cell
Myeloperoxidase
Peroxisomal fatty acyl-coa oxidase generates _______
hydrogen peroxide
2 examples of endogenous free radical scavengers are _____
Uric acid
Melatonin
Name 4 dietary free radical scavenger
Vitamin C
Vitamin E
Carotenoids
Flavonoids
Vitamin E is ____ soluble and protect the membrane against _____
Lipid
Lipid peroxidation
Reduced vitamin c can regenerated the ____ form of ____ by donating electron
Reduced
Vitamin E
