Midterm 3 Flashcards
To achieve become proficient with the materials of Section 6, 7 and 8
Another name for a REDOX reaction
Reduction-oxidation reaction
In redox reactions, one substrate is reduced and the other is _____
oxidized
A reduced + B oxidized —> A oxidized + B reduced
These reactions involve _____ or _____ of electrons
addition, removal
What does the acronym OILRIG stand for?
Oxidation is loss; reduction is gain (of electrons)
pro-oxidant or oxidant
An oxidizing agent; it gains electrons and is reduced in a chemical reaction
Antioxidant
A reducing agent; it loses electrons and is oxidized in a chemical reaction
True or false: In stable molecules, the orbital is occupied by a pair of electrons with opposite spin to each other
True
Free radical
A molecule containing an orbital with an unpaired electron
A free radical seeks to become stable by…
accepting another electron
If molecule A is a free radical and accept an electron from molecule B to become balanced, what happens to molecule B?
Molecule B becomes a free radical
A terminal reaction, in a series of reactions that create free radicals, results from…
the reaction of two free radicals yielding non-radical species or the reaction of the free radical with an antioxidant yielding non-radical species
ROS
Reactive Oxygen Species: compounds derived from the partial reduction of molecular oxygen (O2)
True or false: Reactive Oxygen Species are always free radicals
False… ROS’ do not always contain unpaired electrons
Superoxide radical is formed by…
the one electron reduction of oxygen
O2 + e- —> O2-
What does superoxide spontaneously form when it reacts with hydrogen?
Hydrogen peroxide (H2O2)
O2- + 2H+ —> H202
H2O2 is…
a) a ROS and a free radical
b) a free radical
c) a ROS and has no unpaired electrons
d) a ROS and has an unpaired electron
c)
Which molecule is more stable? Which molecule can travel greater distances? Which molecule can more readily pass through biological membranes? H2O2 or O2-
Hydrogen peroxide (H2O2)
Hydrogen peroxide (H2O2) can easily be converted to a more highly reactive _____ _____.
hydroxyl radical (*OH)
A hydroxyl radical (*OH) and stable hydroxide ion (OH-) are formed by the _____ _____ of _____ in the Fenton reaction
reductive cleavage, hydrogen peroxide (H2O2)
Fenton reaction
A catalytic process that converts hydrogen peroxide into a highly toxic hydroxyl radical (*OH)
The Fenton reaction utilises a _____ metal alongside hydrogen peroxide (H2O2) to produce a _____ and a _____
transition, hydroxyl radical (*OH), hydroxide ion (OH-)
Nitric oxide (NO*)
A nitrogen based free radical that is involved in a number of important biological processes as a signalling molecule
A molecule that acts as a vasomotor factor in blood vessels (promotes vasodilation of smooth muscle)
Nitric Oxide (NO*)
Peroxynitrite (ONOO-)
A ROS that is very long lived and very reactive; it is formed when nitric oxide (NO*) and superoxide radicals (O2-) react
Free radicals, ROS and RNS can lethally damage _____, _____ and _____ which ultimately affects cell function
proteins, DNA, lipids
To minimize the effects of this oxidative damage, organisms have developed _____ defense and _____ damage repair mechanisms
antioxidant, oxidative
Antioxidant defense mechanisms are found in two forms: _____ _____ and _____ _____
antioxidant enzymes, biological antioxidants
The three main antioxidant enzymes are _____ _____, _____, and _____ _____
superoxide dismutase (SOD), catalase, glutathione peroxidase (GPx)
Antioxidant enzymes can be _____ in the _____ as a result of _____ _____
synthesized, body, oxidant stress
True or false: There are several forms of superoxide dismutase (SOD)
True… Two of these are copper-zinc containing superoxide dismutase (CuZnSOD) and manganese containing superoxide dismutase (MnSOD)
Copper-zinc containing superoxide dismutase is found in the _____ while manganese containing superoxide dismutase is found in the _____ ______
cytosol, mitochondrial matrix
True or false: Manganese containing superoxide dismutase (MnSOD) makes up to 12.5% of the total amount of superoxide dismutase (SOD) within the body
False… Manganese containing superoxide dismutase (MnSOD) makes up approximately 15-20% of the total superoxide dismutase (SOD)
Despite being found in the mitochondria, _____ containing superoxide dismutase is synthesized in the ______
manganese, cytosol
Superoxide dismutase (SOD) catalyzes the reaction of superoxide (O2-) and hydrogen to form _____ _____ and _____
hydrogen peroxide (H2O2), oxygen
_____ is found in the mitochondria and other organelles
Catalase
Dismutate
A process of simultaneous oxidation and reduction - used especially of compounds taking part in biological processes
Glutathione peroxidase (GPx) is found in the _____ and the _____
mitochondria, cytosol
Catalase _____ hydrogen peroxide (H2O2) into _____ and _____
water, oxygen
What is the role of glutathione peroxidase (GPx) in relieving oxidant stress?
Glutathione peroxidase (GPx) catalyzes the reduction of hydrogen peroxide (H2O2) to water.
2GSH + H2O2 —> GSSG (glutathione disulfide) + H2O
What is the enzyme responsible for catalyzing this reaction? What molecule is acting as the electron donor (i.e. reducing agent)?
Glutathione peroxidase (GPx), Glutathione (GSH)
Non-enzymatic antioxidants that cannot be synthesized in the body and must be obtained from diet
Antioxidant vitamins
A non-enzymatic antioxidant that can be synthesized in the body
Glutathione (GSH)
What are the two main antioxidant vitamins?
Vitamin E and vitamin C
_____ a water-soluble _____-containing peptide that is found in high concentrations in virtually all cells
Glutathione (GSH), thiol
What is the main function of glutathione (GSH)? What is its secondary function?
To serve as an electron donor in reducing hydrogen peroxide to water with the enzyme glutathione peroxidase. To keep vitamin E and vitamin C in a reduced state.
The ratio of _____ and _____ _____ is essential in determining the antioxidant function of _____ as intracellular _____ _____ in high concentrations inactivates important enzymes
glutathione (GSH), glutathione disulfide (GSSG), glutathione (GSH), glutathione disulfide (GSSG)
To maintain healthy antioxidant function _____ _____ can be exported
glutathione disulfide (GSSG)
Most important fat-soluble antioxidant in the body
Vitamin E (tocopherol)
Tocopherol
Vitamin E: functions as an antioxidant reducing lipid radicals. It can be found in a number of biological membranes including inner mitochondrial membrane
After vitamin E reduces a lipid radical and produces a new lipid non-radical and a vitamin E radical, how can the vitamin E radical become a vitamin E non-radical?
By being reduced by vitamin C or glutathione (GSH)
Most important water-soluble antioxidant in the body
Vitamin C (ascorbic acid)
Ascorbic acid
Vitamin C: functions as an antioxidant by reducing superoxide (O2-), hydroxyl radicals (*OH) or vitamin E radicals. It can be found in the cytosol of a cell as well as the extracellular fluid.
What is the main function of vitamin C (ascorbic acid)? What is its secondary function?
To serve as an electron donor to vitamin E radicals in order to form a less reactive Vitamin C radical, which can be recycled back into vitamin C by glutathione (GSH) and other means. To act as a direct antioxidant to superoxide (O2-) and to hydroxyl radicals (*OH) by reducing them.
Glutathione Redox Cycle
Hydrogen peroxide (H2O2) is reduced to two water molecules and two molecules of glutathione (GSH) are oxidized to a molecule of glutathione disulfide (GSSG) by glutathione peroxidase. Glutathione disulfide (GSSG) is reduced to two molecules of glutathione (GSH) while NADPH is oxidized to NADP+ by glutathione reductase (GR).
True or false: ROS and RNS are important molecules in cell signalling
True
Physiological concentrations of ROS/RNS regulate _____, _____, _____ and _____
growth, differentiation, proliferation, apoptosis
ROS and RNS are important for _____ expression of _____ enzymes
gene, antioxidant
ROS and RNS can also stimulate gene expression of various _____, _____ _____ and _____
cytokines, transcription factors, proteins
Cytokine
A broad and loose category of proteins important in cell signalling. Cytokines can be involved in autocrine signalling, paracrine signalling and endocrine signalling as immunomodulating agents.
ROS and RNS stimulate the gene expression of cytokines, transcription factors and proteins by…
1) Regulating kinase and phosphatase activity, resulting in a signalling cascade through protein phosphorylation and de-phosphorylation
2) Regulating synthesis and breakdown of transcription factors
What are the two main signalling pathways involving ROS or RNS?
Transcription factors (i.e. Nuclear Factor kB) and protein kinases (i.e. mitogen activated protein kinases)
True or false: ROS and RNS are always present in cells/the body whereas antioxidants are always produced
False… ROS and RNS are always PRODUCED whereas antioxidants are always PRESENT IN CELLS/THE BODY
Oxidative stress occurs when…
there is an imbalance between oxidant generation and antioxidant defense
True or false: Any factor that increases the generation of oxidants or decreases antioxidant defense can lead to oxidative stress
True
Biomolecules will be oxidized in tissues and in organs under conditions of _____ _____
oxidative stress
Oxidized biomolecules can include _____, _____ and _____ _____
proteins, lipids, nucleic acids
Why do oxidized proteins have consequences on cell function?
Proteins make a variety of active molecules and structures
Why do oxidized lipids have consequences on cell function?
Lipids make up organelle and cell membranes
Why do oxidized nucleic acids have consequences on cell function?
Nucleic acids make up deoxyribonucleic acid (DNA)
ROS and RNS can make lipids undergo _____, proteins _____, _____ enzymes, and _____ nucleic acids
peroxidation, denature, inactivate, modify
Peroxidation of lipids, denaturation of proteins, inactivation of enzymes and modification of nucleic acids can lead to…
damages in the form of diseases, poisonings and aging.
Six sources of free radicals
1) Ultraviolet light (hydroxyl radical, *OH)
2) Ionizing radiation (hydroxyl radical, *OH)
3) Smoking (superoxide, O2-; hydroxyl radical, OH; and nitric oxide, NO)
4) Air pollution (hydroxyl radical, *OH)
5) Inflammation
6) Metabolism (superoxide, O2-; hydrogen peroxide, H2O2; and hydroxyl radical, *OH)
The main cellular sources of ROS and RNS are _____, _____ _____, _____ _____, _____, and _____ _____ _____
mitochondria, NADPH oxidase, xanthine oxidase, myeloperoxidase, nitric oxide synthase
How does superoxide (O2-) form in the mitochondria?
During mitochondrial respiration electrons pass down through the electron transport chain (ETC) and are accepted by O2 to form water at complex IV. Normally O2 undergoes a four electron reduction, but some electrons leak out of the electron transport train (ETC) and incompletely reduce O2.
Approximately _____ - _____% of all O2 used by the mitochondria is incompletely reduced to superoxide (O2-)
2, 3
What are the major sites of superoxide production in the mitochondrion?
Complex I and complex III
For a given rate of oxidative phosphorylation, decreased mitochondrial content and function _____ ROS generation whereas elevated mitochondrial content and function _____ mitochondrial ROS
increases, decreases
Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase is a _____ subunit complex found in _____
6, membranes
How does nicotinamide adenine dinucleotide phosphate (NADPH) oxidase produce superoxide (O2-)?
It catalyzes the transfer of an electron from reduced NADH (or from NADPH) to oxygen
Where can nicotinamide adenine dinucleotide phosphate (NADPH) oxidase be found?
In immune cells (i.e. neutrophils and macrophages), smooth muscles and skeletal muscles
In immune cells, _____ _____ _____ _____ (NADPH) oxidase functions in host defense by _____ microbes by causing _____ _____ _____
nicotinamide adenine dinucleotide phosphate, killing, free radical damage
Xanthine oxidase (XO) is a _____ enzyme that produces _____ and _____ _____ from the oxidation of _____ and _____
cytosolic, superoxide (O2-), hydrogen peroxide (H2O2), xanthine, hypoxanthine
True or false: Xanthine oxidase participates in cell signalling
True
_____ _____ can act as an NADH oxidase to help maintain reducing equivalents such as NAD+
Xanthine oxidase (XO)
What ROS or RNS does nitric oxide synthase (NOS) produce?
nitric oxide (NO*)
How does nitric oxide synthase (NOS) produce nitric oxide (NO*)?
It catalyzes the oxidation of L-arginine to L-citrulline
There are 3 main _____ _____ _____ isoforms and they are _____ NOS, _____ NOS and _____ NOS
nitric oxide synthase, neuronal (nNOS), inducible (iNOS), endothelial (eNOS)
Where can you find each of the three main NOS isoforms? What are there functions?
Neuronal nitric oxide synthase (nNOS)
- found in skeletal muscle; localized to the sarcolemma region
- associated with dystrophin
Inducible nitric oxide synthase (iNOS)
- found in macrophages
- aid in host defense
Endothelial nitric oxide synthase (eNOS)
- found in endothelial cells
- aids in vasodilation
The most recently discovered isoform of _____ _____ _____ is the _____ isoform (_____NOS)
nitric oxide synthase (NOS), mitochondrial, mt
In which type of muscle are antioxidant concentrations highest?
Slow twitch fibers
Although _____ mitochondria have a higher rate of respiration, they have a lower rate of _____ generation
IMF, ROS
Higher rates of respiration and lower rates of _____ generation are not due to increased levels of _____ _____ _____, but due to increased levels of other _____ and possibly _____ _____
mitochondrial superoxide dismutase (MnSOD), antioxidants, cytochrome c
What two examples suggest that ROS reduce cell replication and induce deoxyribonucleic acid (DNA) damage?
1) Satellite cells incubated with hydrogen peroxide (H2O2) show reduced divisions in culture
2) DNA from the muscle of superoxide dismutase (SOD) deficient animals shows increased oxidative damage
Skeletal muscle from aged animals and humans tends to show an increased activity of _____ _____. This is thought to reflect an age-related increase in _____ generation
antioxidant enzymes, ROS
Mitochondria from aged muscle produces more _____ and _____
superoxide (O2-), hydrogen peroxide (H2O2)
With age there is an increase in _____ _____ to _____, _____ and _____ _____
oxidative stress, membranes, proteins, nucleic acids
Malondialdehyde (MDA)
Also known as lipid peroxide, it is a marker of oxidative damage to lipids
In aged satellite cells, malondialdehyde (MDA) levels _____
increase
Older adults displaying greater fiber type changes in mixed muscle have _____ levels of lipid peroxidation
higher
True or false: Electron transport chain (ETC) complex deficiencies occur in muscle as a result of aging
True
Deficiencies in electron transport chain (ETC) complexes result in increased _____ _____ at the mitochondria and increased _____ _____ damage
ROS generation, muscle oxidative
Muscle contains _____-sensitive sites that are crucial in muscle contraction
redox
Name four sites that are redox-sensitive in muscle that are crucial in muscle contraction
Ryanodine sensitive receptors, sarco/endoplasmic reticulum calcium ATPase (SERCA), actin sites, and myosin sites
Small increases in _____ result in _____ muscle force generation
ROS, increased
Regular _____ can elevate the levels of several _____ in a process known as positive adaptation
exercise, antioxidants
Following training, basal _____ generation is _____ in the muscle; this is deemed to be positive adaptation
ROS, decreased
Oral intake of _____ can decrease _____-induced antioxidant adaptation
vitamins, exercise
True or false: ROS signalling is harmful to exercise-induced mitochondrial biogenesis
False… ROS signalling is critical in exercise-induced mitochondrial biogenesis
What three factors influence positive ROS-induced adaptations?
IkBa (increases), p-IkBa (decreases), and NF-kB (decreases)
What factors influence these positive ROS-induced adaptations relative to disease/aging?
1) Transient increases in ROS generation (and signalling)
2) Lower absolute levels of ROS
3) ROS/RNS source, site of generation, or type of ROS/RNS
True or false: Some level of ROS generation is critical for cellular signalling and force production, but not optimal muscle function
False… Some of level of ROS generation is critical for cellular signalling, optimal muscle function and force production
Several _____-induced muscle adaptations are dependant on sufficient _____ _____
exercise, ROS generation
Altering _____ and _____ levels of ROS may be detrimental to muscle function and adaptation
basal, exercise-induced
True or false: Further research is needed to evaluate the influence that high antioxidant diets/supplementation on long-term cellular adaptions and signalling, as well as its susceptibility to stress/disease
True
_____ and _____ oxidation (oxidative stress) are increased in the skeletal muscle of mdx mice
lipid (MDA), protein (carbonyl
Cell death
A biological process where cells die in response to normal tissue development, cellular stress, injury or disease
There are two types of cell death _____ and _____
necrosis, apoptosis
Necrosis
An accidental form of cell death. Usually occurs during disease or acute injury only and is not part of normal development. Results in rapid cellular swelling and rupturing of the plasma membrane. It leads to a major inflammatory response resulting from release of intracellular material.
Apoptosis
A highly conserved form of cell death. It is an important part of normal tissue development and homeostasis. It can be increased or decreased during numerous diseases.
True or false: Apoptosis is an active process regulated by various intracellular signals
True
Apoptosis results in _____ condensation, _____ shrinking, and membrane _____
chromatin, cell, blebbing
Why is there little to no inflammatory response to apoptosis in contrast to necrosis?
Because during apoptosis the cell membrane remains intact, thus preventing intracellular material from being released
List the five sources of apoptosis initiation
1) Injury (radiation, toxins, free radicals)
2) Withdrawal of growth factors, hormones
3) Receptor-ligand interactions (FAS, TNF-receptor)
4) Cytotoxic T lymphocytes
5) Release of pro-apoptotic molecules from the mitochondria (intrinsic pathway)
Fragmented DNA is said to be the hallmark of what process?
Apoptosis
Alongside fragmented DNA, apoptosis can be recognized by the breakdown of important _____, _____ and _____ proteins
structural, regulatory, repair
True or false: Apoptosis research has become one of the most popular areas of research in science and medicine
True
Inhibition of apoptosis leads to _____ _____ which can result in undesirable tissue growth and associated disorders
cell accumulation
Promotion of apoptosis leads to _____ _____ which can result in undesired tissue _____, _____ _____, decreased _____ _____ and premature death
cell loss, atrophy, retarded development, immune function
List four diseases associated with decreased apoptosis
1) Cancer
2) Some cardiovascular diseases
3) Autoimmune disorders
4) Crohn’s disease (Ulcerative Colitis)
List eight diseases associated with increased apoptosis
1) Cardiovascular diseases
2) Diabetes
3) Neurodegenerative disorders
4) HIV
5) Viral and bacterial infections
6) Osteoporosis
7) Neuromuscular disorders
8) Sarcopenia and atrophy
Caspases
Also known as cysteine aspartic acid proteases. 14 have been identified. Found in inactive form (pro-form) and active form. Are the executers of apoptosis.
Caspase -2, -8, -9 and -12 are known as _____
initiators
Caspase -3, -6 and -7 are known as _____
effectors
Caspases _____ numerous _____ _____ ultimately resulting in apoptosis
cleave, cellular substrates
True or false: Over 800 protein targets of caspases have been identified
False… Over 400 protein targets have been identified
Some of caspases targets that are cleaved in apoptosis are _____, _____ _____ and _____
actin, poly(ADP)ribose polymerase (DNA repair enzyme), lamins (nuclear structure protein)
How many Bcl-2 family proteins have been identified?
At least 25
Bcl-2 family proteins have similar _____ and function to _____ or _____ cell death in a variety of tissues
structures, inhibit, promote
Bcl-2 family proteins can regulate organelle and cell function by acting on various _____
membranes (e.g. mitochondrial, ER/SR, and nuclear)
What are the two main classes of Bcl-2 family proteins?
1) anti-apoptotic (Bcl-2, Bcl-xL)
2) pro-apoptotic (Bax, Bid, Bak)
The ratio of pro-apoptotic to anti-apoptotic proteins in a cell is a measure of what?
The cells susceptibility to apoptosis
What are some apoptosis inducers?
- high levels of free radicals, ROS/RNS
- chemotherapeutic drugs
- high levels of stress hormones
- high cytosolic calcium levels
- UV radiation, ethanol, growth factor withdrawal, nutrient deprivation
What are some apoptosis inhibitors?
- antioxidants (superoxide dismutase, vitamin E, vitamin C, catalase, glutathione peroxidase)
- various growth factors (IGF-I, GH)
What are the steps in the death receptor pathway?
1) Cytokines FasL or TNF-a activate caspases
2) Fas associated death domain (FADD) activated
3) FADD interacts with procaspase 8 and activates caspase 8
4) Procaspase 3 activates caspase 3
5) Apoptosis
In the mitochondrial (intrinsic pathway) the caspase activation is dependent on the release of _____ ______ from mitochondria in the caspase-dependent pathway
cytochrome c
In the mitochondrial (intrinsic pathway) the _____ and _____ _____ translocate to the nucleus and cleaves
apoptosis inducing factor (AIF), endonuclease G (Endo G)
What is the role of apoptosis inducing factor (AIF) in the electron transport chain (ETC)?
It may aid in the assembly of the 46 NADH Dehydrogenase (complex I) components and directly acts as a NADH oxidase for complex I
Cellular stress in the form of _____ _____ can lead to _____/_____ stress and release calcium ions into cytosol
damaged proteins, ER/SR
True or false: Proteolytic enzyme m-calpain is activated when high levels of cytosolic calcium are maintained
True… m-calpain goes on to activate the caspase 12 pathway
