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Flashcards in Free Radical and Antioxidants Deck (29)
1

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

singlet oxygen

2

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

superoxide anion

3

transfer of two electrons to oxygen

hydrogen peroxide

4

transfer of three electrons to oxygen

generates hydroxyl radical and hydroxide anion
hydroxyl radical is most reactive ROS, half-life of nanoseconds

5

transfer of four electrons to oxygen

water

6

What is a by-product of ETS?

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

7

What organelle is a major source of ROS?

mitochondria

8

NADPH/cytochrome oxdiases are a source of which ROS?

superoxide anion

9

Xanthine oxidase is a source of which ROS?

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

10

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

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

11

How does chronic alcohol metabolism stress the liver?

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

12

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

superoxide dismutase

13

heme-containing enzyme that detoxifies hydrogen peroxide
- antioxidant

catalase

14

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

glutathione peroxidase

15

- water-soluble electron donor to many types of free radicals
- oxidized to dehydroascorbic acid
- antioxidant

ascorbic acid (vitamin C)

16

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

Vitamin E (tocopherols)

17

- 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

Vitamin A (retinol)

18

- water-soluble
- metabolic antioxidant
- plant extracts: green tea, grapes, red wine, chocolate

Polyphenols (flavonoids)

19

major metabolic antioxidant in serum

uric acid

20

- lipid soluble metabolic antioxidant
- unconjugated form can donate electrons to radicals

Bilirubin
- converts back to biliverdin

21

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

- integrity and function of cell membrane
- most serious damage to membranes

22

Summarize the process of lipid peroxidation

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

23

What leads to large amounts of ROS in RBCs?

high oxygen saturation

24

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

how RBC control oxidative stress

25

Explain how methemoglobin reductase can reduce oxidative stress in RBCs

- replaces electron to the iron in heme
- repairs the oxidative damage by reducing the iron and converts methemoglobin back to Hb

26

Which ROS does the most damage to DNA?

hydroxyl radical
- causes DNA double strand breaks
- interferes with replication and transcription by binding to guanine bases

27

What does ROS cause protein damage?

- causes formation of incorrect disulfide bonds
- proteins become inactive and initiate its destruction

28

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

Nitric Oxide

29

- covalently modifies lipies, DNAs, and proteins
- formed from superoxide and peroxynitrate anions
- very reactive

Peroxynitrite