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Biochemistry 2 > Reactive Oxygen Species > Flashcards

Reactive Oxygen Species Flashcards

1
Q

What is the Fenton reaction?

A

Fe2+ H2O2 = OH + Fe3 and OH-

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2
Q

What are 3 types of ROS?

A

Hydroxyl radical, superoxide, hydrogen peroxide

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3
Q

Why is H2O2 a ROS?

A

It can create a hydroxyl radical and diffuse throughout the body

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4
Q

What is a free radical?

A

an atom, molecule, or ion with unpaired valence electrons

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5
Q

What is the most reactive RNOS?

A

Peroxynitrorous acid

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6
Q

Reactive oxygen and free radicals initiate what?

A

Cell injury

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7
Q

What does oxygen toxicity result from?

A

Reactive oxygen species and free radicals

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8
Q

Antioxidant defenses have evolved in parallel with what?

A

Evolution of aerobic metabolism

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9
Q

How are ROS generated?

A

One electron transfers

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10
Q

What is the Harber-Weiss reaction?

A

O2- + h2o2 with H+ —— O2 + h2o + OH

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11
Q

The OH radical is especially dangerous in which cell type? Why?

A

RBC; leads to anemia

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12
Q

What is the most reactive ROS?

A

Hydroxyl radical

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13
Q

How does peroxynitrous induce damage?

A

Adds nitronium ions to aromatic rings, especially aromatic aa

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14
Q

What are 3 normal biological processes that generate superoxides?

A

Phase I detox (p450), ETC (CoQ), LOX and COX

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15
Q

What immune system cells generate ROS?

A

Neutrophils (respiratory burst)

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16
Q

Which lipids are most susceptible to oxidative damage?

A

PUFA

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17
Q

What are the 4 phases of free radical damage?

A

Initiation, propagation, termination, degradation

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18
Q

What are 3 types of damage free radicals can produce in cells?

A

PUFA very susceptible, amino acid residues, DNA mutation from epoxides

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19
Q

What are 3 ways antioxidants reduce ROS activity?

A

Before ROS are formed, get rid of them when they are formed, repair oxidative damage

20
Q

What are the 3 antioxidant enzymes?

A

Glutathione peroxidase, superoxide dismutase, catalase

21
Q

What is the first line of defense against oxidative damage?

A

Antioxidant enzymes

22
Q

What is the second line of defense against ROS?

A

Free radical scavengers like Vit C and Vit E

23
Q

What are the substrates for GPX?

A

Selenium

24
Q

Where are GPX and selenium in the cell?

A

Cytosol and mitochondrial matrix

25
Q

What are the substrates for SOD?

A

Cu, Zn (cytosol); Mn (mitochondria)

26
Q

What are the substrates for CAT?

A

Iron and peroxisomes

27
Q

GPX acts on which ROS?

A

H2O2

28
Q

SOD acts on which ROS?

A

Superoxide

29
Q

CAT acts on which ROS?

A

H2O2

30
Q

Glutathione is a co substrate for which enzyme?

A

GPX

31
Q

How do Vit C, E, and glutathione act as antioxidants?

A

Reducing agents

32
Q

Where is vitamin E in the cell?

A

Membranes and lipoproteins (plasma membrane and lysosomes)

33
Q

Where is Vit C in the cell?

A

Cytosol and mitochondria

34
Q

Where does absorption if vitamin C occur?

A

Distal small intestine

35
Q

How is vitamin C absorbed?

A

Sodium-dependent ascorbate transporter (SVCT)

36
Q

Where is SCVT1?

A

Distal small intestine

37
Q

How do most cells acquire vitamin C?

A

Through SCVT2 and GLUT transporters

38
Q

What does ascorbate do as a primary antioxidant?

A

Neutralizes radical oxygen and nitrogen species, peroxides, and superoxides

39
Q

Why must dehydroascorbate be reduced?

A

Has a short half life, must be reduced to avoid loss as diketogulonic acid

40
Q

Regeneration of the reduced form of Vitamin C involves which reducing agents?

A

NADH or glutathione

41
Q

Regeneration of the reduced form of Vitamin C involves which enzymes?

A

NADH reductase, dehydroascorbate reductase, thioredoxin reductase

42
Q

What are 3 points to remember for why vitamin C is such an important dietary antioxidant?

A

Major water soluble antioxidant, can neutralize both oxygen and nitrogen ROS, ascorbate radical is stable

43
Q

How do vitamin E and vitamin C differ as antioxidants?

A

Vitamin C acts as a direct antioxidant while vitamin E is a stable place to put the electrons until vitamin C can remove it

44
Q

What 2 things make up vitamin E?

A

Tocopherols, tocotrienols

45
Q

What component of vitamin E is selectively extracted in the liver?

A

a-tocopherol

46
Q

Where does vitamin E accumulate?

A

Membranes and lipoproteins

47
Q

How does vitamin E function as an antioxidant?

A

Terminates membrane lipid oxidation through single electron transfers, forming a stable tocopherol species

Biochemistry 2 (13 decks)

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