Oxidative stress and antioxidant systems

Question 1

What is a free radical?

Answer 1

A molecule with an unpaired valence electron.

Question 2

What is the oxygen paradox

Answer 2

Anaerobic organisms evolved first, and oxygen is inherently dangerous to them because of free radical generation, and anaerobic organisms typically don’t have antioxidant systems.

Question 3

What is an oxidant

What is a reductant

Answer 3

Oxidant: something that oxidizes another chemical by: taking electrons, taking hydrogen, or adding oxygven

Reductant: Adds electrons, adds hydrogen, or removes oxygen.

Question 4

half life of hydrogen peroxide

half life of hydroxyl radicals

Answer 4

H2O2, a few minutes

hydroxyl radical, nanoseconds.

Question 5

What are ROS?

Answer 5

ROS are atoms or molecules formed by the incomplete reduction of oxygen.

Radical ROS:
Superoxide O2-
Hydroxyl radical OH-
Hydroperoxyl HO2-

Non-radical ROS:
Hydrogen peroxide H2O2
Singlet oxygen 1O2
Ozone O3

Question 6

What are Reactive Nitrogen Species

Answer 6

Radical RNS:
Nitric Oxide NO
Nitrogen Dioxide NO2-

Non-radical:
Peroxynitrite ONOO-

Question 7

What are the steps in the complete oxidation of oxygen

Answer 7

O2

O2- superoxide anion

H2O2 hydrogen peroxide

OH- hydroxyl radical

H2O water

Question 8

What is the most biologically reactive ROS?

Answer 8

Hydroxyl radicals.

Question 9

What are the good and bad roles of ROS?

Answer 9

bad: increased ROS load causes apoptosis
Damage DNA/proteins/Lipids in the cell

good: essential for microbial defense
Platelets use ROS as signaling to recruit more platelets and promote coagulation.

Question 10

What enzymes remove ROS

Answer 10

Superoxide dysmutase
Catalse
guaiacol peroxidase (GPX)

Glutathione, not an enzyme tho

Question 11

Diseases that ROS are involved in pathogenesis

Answer 11

Alzhemiers, Parkinsons, Schizophernia

Cancer

Cataracts

Hypertension, Atherosclerosis, Ischemia

Asthma

Chronic inflammatory disorders:
Lupus, Multiple sclerosis
Rheumatoid arthritis

Question 12

Exogenous sources of radicals

Answer 12

Ionizing or UV radiation

Pollutants

Cigarette smoke

Drugs and xenobiotics

Question 13

How does UV radiation generate free radicals?

Answer 13

from hydrogen peroxide.

Splits it into two hydroxyl radicals

Question 14

How does gamma radiation generate ROS?

Answer 14

Can generate hydroxyl radicals from water.

Question 15

Enzymes that generate ROS endogenously

Answer 15

Lipoxygenase

Xanthine oxidase

Cyclooxygenase

Cytochrom p450 Monooxygenase

NO synthase

NADPH oxidase

Byproduct of the Electron transport chain and partial oxygen reduction.

Question 16

What is the common component of Cytpchrome p450 enzymes.

Answer 16

Heme is a cofactor

Question 17

What enzyme generates ROS in the ER after alcohol consumption

Answer 17

CYP2E1
a mixed function oxidase (not alcohol dehydrogenase)
It is IN THE ER

Converts ethanol to acetaldehyde (Reducing it), and uses NADPH and O2 as cofactors, generating NADP+ and H2O, or can generate reactive oxygen species.

Question 18

What reaction does Xanthine oxidase catalyze?

Answer 18

hypoxanthine, O2, and H20 -> H2O2 and xanthine

xanthine O2 and H20 –> uric acid and H2O2.

Question 19

What precursor does NOS use to synthesize NO?

Answer 19

L-Arginine

Question 20

What is the main enzyme neutrophils use to generate ROS?

Answer 20

NADPH oxidase.
Generates superoxide anions O2-
Adds a single electron to O2.

Question 21

What is the organelle whose main function is generating ROS and RNS?

What are a few examples of eznymes in it?

Answer 21

Peroxisomes

NO synthase
Xanthine oxidase
Urate oxidase
Acyl-CoA oxidase
D-amino acid oxidase

Question 22

What is the main enzyme neutrophils use to generate RNS? What other products can it generate?

Answer 22

Myeloperoxidase.

MPO uses H2O2 and NO2 (nitrite) to generate RNS intermediates

It can also generate several very strong acids:
H2O2 and Cl, Br, SCN,

hypochlorous HOCl
hypobromous HOBr
hypothiocyanous acids HOSCN

Or it can generate Tyrosyl radicals from H2O2 and Tyrosine.

Question 23

List 5 endogenous anti-oxidants

Answer 23

Glutathione (replenished by gluathione reductase)

Catalse

Superoxide Dismutase

CoEnzyme Q-10

Cytochrome C Peroxidase

Question 24

List some dietary anti-oxidants.

Answer 24

ACE vitamins, vitamins A, C, E

Alpha lipoic acid

N-acetyl cystine

Polyphenols
Green tea and Olive oil

Proanthocyanidins
Red wine
Blueberrys
Chocolate

Ginsengs.