Oxygen

Question 1

oxygen is essential for all life of ____ organisms

Answer 1

aerobic

Question 2

O2 is highly reactive in ____ reactions at ____ temperatures

Answer 2

combustion; high

Question 3

O2 is relatively inert at _____

Answer 3

body temperatures

Question 4

O2 has high ____ for ____ reactions

Answer 4

activation energy; oxidation

Question 5

about 90% of oxygen usage is committed to _____

Answer 5

oxidative phosphorylation

Question 6

oxidation is the ___ of electrons or an ____ in oxidation state by a molecule, atom, or ion

Answer 6

loss; increase

Question 7

reduction is the ___ of elections or a ____ in oxidation state by a molecule, atom, or ion

Answer 7

gain; decrease

Question 8

the formal oxidation state is the hypothetical ___ that an atom would have if all bonds to atoms of different elements were 100% ____

Answer 8

charge; ionic

Question 9

oxidation/reduction reactions happen simultaneously; each alone are called a ____

Answer 9

half-reaction

Question 10

reactivity of O2 requires ___ or ____

Answer 10

high heat; activation energy

Question 11

at body temperatures, activation of O2 is always activated by ____

Answer 11

metal ions (iron, copper, or manganese)

Question 12

____ are partially reduced, reactive forms of oxygen

Answer 12

reactive oxygen species (ROS)

Question 13

the first reduction product is the anion radical _____, which is in equilibrium with the weak acid, _____

Answer 13

superoxide; hydroperoxyl radical (pKa 4.5)

Question 14

reduction of superoxide yields ____

Answer 14

hydrogen peroxide (H2O2)

Question 15

reduction of hydrogen peroxide causes a homolytic cleavage reaction which releases ____ and _____

Answer 15

hydroxyl radical; hydroxide ion

Question 16

____ is the end product of complete reduction of O2

Answer 16

water

Question 17

____ occurs when the rate of ROS generation exceeds the ability to neutralize them

Answer 17

oxidative stress

Question 18

oxidative stress results in an increase in ____ to ____ (cell proteins, lipids, and DNA)

Answer 18

oxidative damage; biomolecules

Question 19

reactive oxygen species (ROS) used by ____ to destroy pathogens; also a feature of _____ diseases like arthritis, atherosclerosis, SLE, or diabetes)

Answer 19

immune cells; inflammatory

Question 20

disturbances in the normal redox state of cells can cause toxic effects through the production of ____ and ____ that damage all components of the cell, including proteins, lipids and DNA

Answer 20

peroxides; free radicals

Question 21

most prevalent ROS in blood and tissues is ____, which is a stable molecule unless reacted with metal

Answer 21

hydrogen peroxide (H2O2)

Question 22

____ is most reactive and damaging species

Answer 22

OH radical

Question 23

other ROS include ____, ____ and _____

Answer 23

superoxide anion (ion and radical); hypochlorite ion; hydroperoxyl radical

Question 24

a radical is a cluster of atoms, one of which contains an ____ in its outermost shell of electrons

Answer 24

unpaired electron

Question 25

ROS formed by 3 major mechanisms in vivo:

Answer 25

1. by reaction of oxygen with de-compartmentalized metal ions (Fenton and Haber-Weiss rxns) 2. as a side rxn of mitochondrial electron transport 3. normal enzymatic rxns (formation of H2O2 by fatty acid oxidases in the peroxisome)

Question 26

fenton first described the oxidizing power of ____ and ____; this rxn generates the strong oxidant ____ (____ catalyzes the same rxn)

Answer 26

Fe2+ ; H2O2; hydroxyl radical; Cu+

Question 27

the H-W reaction describes the production of hydroxyl radical from ____ and _____

Answer 27

superoxide anion radical; hydrogen peroxide

Question 28

under phys. conditions, the H-W rxn is catalyzed by ____ metal ions

Answer 28

redox-active

Question 29

oxidative stress is an imbalance betw ____ and ____ systems

Answer 29

pro-oxidant; antioxidant

Question 30

ROS can be generated by the _____ in mitochondria; can be caused by ____ injury following myocardial infarction

Answer 30

mitochondrial electron transport chain; ischemia/reperfusion

Question 31

ROS generated by activation of ____ during inflammatory conditions (example is myeloperoxidase converting H2O2 and Cl- to hypochlorous acid (HOCl)

Answer 31

polymorphonuclear leukocytes (PMN)

Question 32

one of the most sensitive sites of ROS damage is at the ____ because they are rich in _____ which react readily with ROS

Answer 32

cell membrane; polyunsaturated fatty acids (PUFA)

Question 33

damage to cell membrane leads to reduced ____ and ____ and can result in ____

Answer 33

integrity; function; apoptosis

Question 34

the hydroxyl radical is known to react with all components of the DNA molecule, damaging both the ____ and ____ bases and also the ____

Answer 34

purine; pyrimidine; deoxyribose backbone

Question 35

most extensively studied DNA lesion is ____

Answer 35

8-OH-G (8-oxoguanine or 8-hydroxygunanine)

Question 36

permanent mod. of genetic material resulting from these oxidative damage incidents is the first step to ____, ____ and ____

Answer 36

mutagenesis; carcinogenesis; aging

Question 37

the side chains of all ____ residues of proteins , in particular ____ and ____ residues are susceptible to oxidation by the action of ROS

Answer 37

amino acid; cysteine; methionine

Question 38

cells of the ___ must make hydrogen peroxide in order to attach ____ to ____ in the synthesis of thyroxine

Answer 38

thyroid gland; iodine atoms; thyroglobulin

Question 39

____ and ____ must generate ROS in order to kill some types of bacteria they engulf by phagocytosis

Answer 39

macrophages; neutrophils

Question 40

defense mechanisms against free radical -induced oxidative stress involve:

Answer 40

- preventive mechanisms - repair mechanisms - physical defenses

Question 41

cells have a variety of ____ defenses against the harmful effects of ROS

Answer 41

enzymatic

Question 42

____ converts 2 superoxide anions into a molecule of hydrogen peroxide and oxygen

Answer 42

superoxide dismutase (SOD)

Question 43

___ converts hydrogen peroxide to water and oxygen

Answer 43

catalase

Question 44

small molecules that are antioxidant

Answer 44

vitamins A, C, and E and uric acid

Question 45

diseases developed by ROS

Answer 45

inflammation (arthritis, SLE, diabetic complications, reperfusion) infection cancer-mutagenesis aging