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Biochem Final > Free Radical and Antioxidants > Flashcards

Free Radical and Antioxidants Flashcards

1
Q

oxygen in the ground state that has absorbed light or other sources
“excited”
- not a radical but still reactive

A

singlet oxygen

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2
Q
  • generated by one-electron reduction of molecular oxygen, usually involve a metal catalyst
  • not very reactive
A

superoxide anion

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3
Q

transfer of two electrons to oxygen

A

hydrogen peroxide

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4
Q

transfer of three electrons to oxygen

A

generates hydroxyl radical and hydroxide anion

hydroxyl radical is most reactive ROS, half-life of nanoseconds

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5
Q

transfer of four electrons to oxygen

A

water

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6
Q

What is a by-product of ETS?

A

ROS

- instead of transferring the electron to complex III, it gets put on oxygen to make superoxide anion

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7
Q

What organelle is a major source of ROS?

A

mitochondria

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8
Q

NADPH/cytochrome oxdiases are a source of which ROS?

A

superoxide anion

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9
Q

Xanthine oxidase is a source of which ROS?

A

2 peroxide is produces when reducing hypoxanthine and xanthine to uric acid

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10
Q

Reduction of iron and copper ions are a source of which ROS?

A 
can donate electron to either oxygen or peroxide:
superoxide anion (oxygen) and hydroxyl radical (peroxide)
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11
Q

How does chronic alcohol metabolism stress the liver?

A

1) oxidative stress from hydrogen peroxide damages membranes and kills cells
2) DNA damage from hydroxyethyl production produces mutations and predisposes to cancer

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12
Q

located in cytoplasm and mitochondria to convert superoxide into the less reactive oxygen intermediate hydrogen peroxide
- antioxidant

A

superoxide dismutase

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13
Q

heme-containing enzyme that detoxifies hydrogen peroxide

- antioxidant

A

catalase

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14
Q

uses the electrons from reduced glutathione to reduce hydrogen peroxide
- antioxidant

A

glutathione peroxidase

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15
Q
  • water-soluble electron donor to many types of free radicals
  • oxidized to dehydroascorbic acid
  • antioxidant
A

ascorbic acid (vitamin C)

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16
Q
  • lipid-soluble radical scavenger
  • present in membranes where it prevents damage from free radicals as well as from lipid peroxidation
  • antioxidant
A

Vitamin E (tocopherols)

17
Q
  • lipid-soluble compound that functions as an electron donor for the reduction of radicals such as lipid peroxides
  • “quenches” the vibrating energy from the singlet oxygen
  • antioxidant
A

Vitamin A (retinol)

18
Q
  • water-soluble
  • metabolic antioxidant
  • plant extracts: green tea, grapes, red wine, chocolate
A

Polyphenols (flavonoids)

19
Q

major metabolic antioxidant in serum

A

uric acid

20
Q
  • lipid soluble metabolic antioxidant

- unconjugated form can donate electrons to radicals

A

Bilirubin

- converts back to biliverdin

21
Q

What does peroxidative breakdown of polyunsaturated fatty acids (PUFAs) affect?

A
  • integrity and function of cell membrane

- most serious damage to membranes

22
Q

Summarize the process of lipid peroxidation

A

PUFA»Lipid Radical»Lipid Peroxide (unstable), reacts with itself»malondialdehyde (mutagenic, reacts with purine bases in DNA)

23
Q

What leads to large amounts of ROS in RBCs?

A

high oxygen saturation

24
Q

1) glutathione peroxidase
- destroys hydrogen and organic peroxides
2) superoxide dismutase
- destroys superoxide
3) catalase
- converts hydrogen peroxide
4) high concentrations of GSH, Vit C, Vit E
- directly react with ROS
5) methemoglobin reductase

A

how RBC control oxidative stress

25
Q

Explain how methemoglobin reductase can reduce oxidative stress in RBCs

A
  • replaces electron to the iron in heme

- repairs the oxidative damage by reducing the iron and converts methemoglobin back to Hb

26
Q

Which ROS does the most damage to DNA?

A

hydroxyl radical

  • causes DNA double strand breaks
  • interferes with replication and transcription by binding to guanine bases
27
Q

What does ROS cause protein damage?

A
  • causes formation of incorrect disulfide bonds

- proteins become inactive and initiate its destruction

28
Q
  • free radical that acts as a powerful vasodilator
  • modifies proteins in signal transduction pathways
  • most effective through activation of guanylate cyclase
A

Nitric Oxide

29
Q
  • covalently modifies lipies, DNAs, and proteins
  • formed from superoxide and peroxynitrate anions
  • very reactive
A

Peroxynitrite

Biochem Final (21 decks)

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