Free Radicals and Antioxidants

Question 1

What is the most reactive ROS?

Answer 1

hydroxyl radical

Question 2

What cytochrome p450 isoform is responsible for alcohol degradation?

Answer 2

CYP450E1

Question 3

What type of radical does CYP450E1 produce?

Answer 3

hydroxyethyl radical

Question 4

What are the five sources of ROS?

Answer 4

quinone

NADPH/cytochrome oxidase

CYP450E1

xanthine oxidase

Free iron and copper ions

Question 5

How do free iron and copper contribute to the production of ROS?

Answer 5

by donating an electron to molecular oxygen or hydrogen peroxide

Question 6

What is Iron bound to?

Answer 6

ferritin or transferrin

Question 7

What is copper bound to?

Answer 7

ceruloplasmin

Question 8

What protein in heme provides protection against oxidation?

Answer 8

globin

Question 9

How can radiation kill cancer?

Answer 9

radition can split a water molecule into hydrogen and hydroxyl radical

Question 10

What is the function of superoxide dimutase?

Answer 10

to convert superoxide radical into H2O2

Question 11

What is the function of catalase?

Answer 11

to convert hydrogen peroxide into water

Question 12

What is the function of ascorbic acid?

Answer 12

water soluble electron donor to many types of free radicals

Question 13

Where is vitamin E present? What is its function?

Answer 13

membranes. radical scavenger.

Question 14

Vitamin E prevent what two types of damage?

Answer 14

damage from free radicals and lipid peroxidation

Question 15

What property gives vitamin A its ability to reduce oxidative damage to membranes?

Answer 15

series of unconjugated double bonds

Question 16

How does glutathione protect against oxidative stress?

Answer 16

glutathione can donate an electron to a free radical from its thiol group and form a homodimer

Question 17

What is another name for polyphenols?

Answer 17

Flavonoids

Question 18

What are polyphenols?

Answer 18

water soluble antioxidants found in green tea, grapes, red wine and chocolate

Question 19

What is a major antioxidant of the cytoplasm?

Answer 19

uric acid

Question 20

What water insoluble compound can donate an electron to free radicals?

Answer 20

bilirubin

Question 21

After donating an electron, what does bilirubin become?

Answer 21

biliverdin

Question 22

How do antioxidants become reduced after they donate an electron?

Answer 22

mostly by NADPH

Question 23

What in RBCs tends to promote oxidative damage?

Answer 23

high oxygen content

Question 24

What compound in RBCs destroys hydrogen and organic peroxides?

Answer 24

glutathione peroxidase

Question 25

What three components of RBCs directly react with ROS?

Answer 25

GSH, Vitamin C and Vitamin E

Question 26

What is the function of methemoglobin reductase?

Answer 26

to replace oxidized iron in heme

Question 27

What molecule can extract an electron from the iron in heme?

Answer 27

hydrogen peroxide

Question 28

What is the most serious damage to membrane by radicals?

Answer 28

peroxidation of polyunsaturated fatty acids

Question 29

What are the three steps to lipid peroxidation?

Answer 29

1. hydroxyl radical removes electron from PUFA 2. lipids fadicals form lipid peroxides 3. Lipid peroxides abstract electrons from other PUFAs

Question 30

What lipid peroxidation product is mutagenic?

Answer 30

Malondialdehyde

Question 31

Why is malondialdehyde mutagenic?

Answer 31

malondialdehyde reacts with purine bases in DNA

Question 32

Plasma concentration of what is a good marker for oxidative stress?

Answer 32

malondialdehyde

Question 33

Hydroxyl radical does the most serious damage to what?

Answer 33

DNA

Question 34

What does hydroxyl radical do to DNA?

Answer 34

produces double-stranded breaks

Question 35

In proteins, what do ROS extract electrons from?

Answer 35

thiol groups

Question 36

What does removing electrons from thiol groups do?

Answer 36

produces incorrect double bonds

Question 37

Is nitric oxide a free radical?

Answer 37

Yes

Question 38

What is peroxynitrite formed from?

Answer 38

superoxide and peroxynitrate

Question 39

What vitamin has an extensive system of conjugated double bonds?

Answer 39

Vitamin A

Question 40

Excluding glutathione, what are three other metabolic antioxidants?

Answer 40

uric acid, bilirubin, polyphenols

Question 41

What reduction equivalent is capable of reducing antioxidant?

Answer 41

NADPH

Question 42

What makes malondialdehyde mutagenic?

Answer 42

It reacts with purine bases

Question 43

Can malondialdehyde be measured?

Answer 43

yes. it is a good measure of oxidative stress.

Question 44

What base can hydroxyl radical bond with?

Answer 44

guanine

Question 45

In proteins, ROS extract an electron from what group?

Answer 45

thiol

Question 46

What is peroxynitrite formed from?

Answer 46

peroxynitrate and superoxide