Chapter 8.2: Antioxidants (Nov 17)

Question 1

Where do reactive oxygen species (ROS) come from?

List 4

Answer 1

1. contained in the diet
2. arise from within the body
3. natural byproduct of oxygen metabolism
4. immune response- oxidative burst

Question 2

how do ROS come from the diet?

Answer 2

reactive oxygen species can be contained in the diet as oxidatively damaged fats and oils

Question 3

how do ROS arise from within the body?

Answer 3

• created by pathogens
• exposure to external factors
• part of the normal biology of organisms

Question 4

How do ROS arise from immune responses?

Answer 4

oxidative bursts!

= a rapid production of huge amounts of ROS in response to a pathogen infection or tumor

Question 5

animal ___ have several means of protection against oxidative damage:

Answer 5

tissues

preventative antioxidants

Question 6

preventative antioxidants prevent oxidation by reducing the rate of ___ ___

Answer 6

chain initiation

Question 7

List 3 antioxidant enzymes

Answer 7

• superoxide dismutase (SOD)
• catalase
• glutathione peroxidase

Question 8

what are the 2 forms of superoxide dismutase (SOD)?

Answer 8

1. MnSOD: protects mitochondria from ROS produced through normal metabolism
2. CuZnSOD: in cytosol and nucleus

Question 9

catalase is an antioxidant enzyme.

• what does it contain?
• what does it do?

Answer 9

• contains 4 heme iron groups

- decomposition of hydrogen peroxide to water and oxygen

Question 10

glutathione peroxidase is an antioxidant enzyme.

• It is a _____
• what does it do?

Answer 10

• selenoprotein (selenium is part of the active site)

- reduces lipid hydroperoxides to alcohols, and hydrogen peroxide to water

Question 11

what do chain-breaking antioxidants do?

Answer 11

stops oxidative chain reaction by turning free radicals (oxidatively damaged) into stable chemicals

Question 12

oxidation can result in ___ ____

Answer 12

cell damage

• polyunsaturated fatty acids
• phospholipids of cell membranes

Question 13

what makes vitamin E effective as an antioxidant?

Answer 13

it has a fatty acid type tail

- also, it is lipid soluble

Question 14

how does vitamin E act as an antioxidant?

Answer 14

• lipid soluble –> is incorporated into cell membrane
• it can “quench” the unpaired e-
• Vitamin E radical can be regenerated to Vitamin E via reaction with vitamin C

Question 15

What happens to the Vitamin E radical (has an unpaired e-, after quenching the unpaired e- from oxidative damage)

Answer 15

Vitamin E radical can be regenerated to Vitamin E via reaction with vitamin C