Reactive Oxygen Species

Question 1

Name 3 important cellular redox pairs

Answer 1

NADP/NADPH, NAD+/NADH, GSSG/GSH

Question 2

What is GSH?

Answer 2

GSH (glutathione) is a key cellular reducing and detoxifying agent

Question 3

When is the cytoplasm more reduced? When is it more oxidized?

Answer 3

Reduced = entering cell division
Oxidized = differentiated cells

Question 4

What organelles are more reduced? What organelles are more oxidized?

Answer 4

Nucleus/mitochondria = more reduced
ER = more oxidized

Question 5

How do superoxide radicals form?

Answer 5

Electrons leak from Electron Transport Chain to form superoxide radical (O2 radical), which acts as a nucleophile

Question 6

What happens when superoxide radical reacts with itself?

Answer 6

Can form H2O2

Question 7

What harmful effects can ensue from biological H2O2 accumulation?

Answer 7

H2O2 can react with Fe 2+ to produce OH radicals, which can initiate an autocatalytic radical chain reaction and damage the lipid bilayer

Question 8

What is the danger of singlet oxygen?

Answer 8

Singlet oxygen can form from H2O2 or superoxide. Can damage aromatics and conjugated alkenes. Can form alpha,beta-unsaturated alkdehyde—very dangerous.

Question 9

What is the biological function of NO?

Answer 9

Signaling molecule, regulates blood pressure, and inhibits clotting

Question 10

What are 3 reactive nitrogen species?

Answer 10

NO2, ONOO-, NO

Question 11

What is respiratory burst? What enzyme is involved?

Answer 11

Macrophages and neutrophils make lots of ROS, use them to destroy microorganisms and damaged cells

NADPH oxidase makes superoxide during respiratory burst
Consumes 100x more oxygen

Question 12

What is the danger of singlet oxygen?

Answer 12

Can form from H2O2 or superoxide.

Damages aromatics and conjugated alkenes. Can form alpha,beta-unsaturated aldehyde (very dangerous).

Question 13

What is the biological function of NO?

Answer 13

Signaling molecule, regulates blood pressure and inhibits clotting

Question 14

What is respiratory burst? What enzyme is involved?

Answer 14

Macrophages and neutrophils make lots of ROS, use to destroy microorganisms and damaged cells

NADPH oxidase makes superoxide during respiratory burst
-Consumes 100x more oxygen

Question 15

What reaction does superoxide dismutase catalyze?

Answer 15

2 Superoxide radicals + 2 H+ -> H2O2 + O2

Question 16

What reaction does catalase catalyze?

Answer 16

2 H2O2 -> O2 + H2O

Question 17

What reaction does glutathione peroxidase catalyze?

Answer 17

2 GSH + R-O-OH -> GSSG + ROH + H2O

• Uses GSH to control peroxide levels
• Reduces H2O2 to H2O and transforms organic peroxides to alcohol
• Part of glutathione system

Question 18

What is alpha-tocopherol

Answer 18

Lipid soluble radical scavenger, protects membrane

AKA Vitamin E

Question 19

What is ascorbic acid?

Answer 19

Water soluble radical scavenger, protects membrane

Regenerates alpha-tocopherol

VIT C

Question 20

What is beta-carotene?

Answer 20

Lipid soluble scavenger

VIT A PRECURSOR

Question 21

Why are unsaturated fats liquid at room temperature?

Answer 21

Weaker intermolecular forces

Trans fats behave more like saturated FAs

Question 22

What are the two nomenclature styles for FAs?

Answer 22

1) X:Y^deltaN
2) X:Y omega-N

X = number of carbons
Y = number of double bonds
N = carbon atom that forms double bond
1) count from carboxyl end
2) count from omega end

1) lists all double bonds in structure
2) only lists first double bond from omega-end

Question 23

What FAs are essential in humans?

Answer 23

Linoleic and alpha-linoleic acids
(aka “omega-6” and “omega-3”)

Omega-6 is proinflammatory
Omega-3 is antiinflammatory