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Biochem > Oxygen > Flashcards

Oxygen Flashcards

1
Q

oxygen is essential for all life of ____ organisms

A

aerobic

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2
Q

O2 is highly reactive in ____ reactions at ____ temperatures

A

combustion; high

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3
Q

O2 is relatively inert at _____

A

body temperatures

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4
Q

O2 has high ____ for ____ reactions

A

activation energy; oxidation

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5
Q

about 90% of oxygen usage is committed to _____

A

oxidative phosphorylation

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6
Q

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

A

loss; increase

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7
Q

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

A

gain; decrease

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8
Q

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

A

charge; ionic

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9
Q

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

A

half-reaction

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10
Q

reactivity of O2 requires ___ or ____

A

high heat; activation energy

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11
Q

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

A

metal ions (iron, copper, or manganese)

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12
Q

____ are partially reduced, reactive forms of oxygen

A

reactive oxygen species (ROS)

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13
Q

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

A

superoxide; hydroperoxyl radical (pKa 4.5)

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14
Q

reduction of superoxide yields ____

A

hydrogen peroxide (H2O2)

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15
Q

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

A

hydroxyl radical; hydroxide ion

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16
Q

____ is the end product of complete reduction of O2

A

water

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17
Q

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

A

oxidative stress

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18
Q

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

A

oxidative damage; biomolecules

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19
Q

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

A

immune cells; inflammatory

20
Q

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

A

peroxides; free radicals

21
Q

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

A

hydrogen peroxide (H2O2)

22
Q

____ is most reactive and damaging species

A

OH radical

23
Q

other ROS include ____, ____ and _____

A

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

24
Q

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

A

unpaired electron

25
Q

ROS formed by 3 major mechanisms in vivo:

A
  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)
26
Q

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

A

Fe2+ ; H2O2; hydroxyl radical; Cu+

27
Q

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

A

superoxide anion radical; hydrogen peroxide

28
Q

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

A

redox-active

29
Q

oxidative stress is an imbalance betw ____ and ____ systems

A

pro-oxidant; antioxidant

30
Q

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

A

mitochondrial electron transport chain; ischemia/reperfusion

31
Q

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

A

polymorphonuclear leukocytes (PMN)

32
Q

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

A

cell membrane; polyunsaturated fatty acids (PUFA)

33
Q

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

A

integrity; function; apoptosis

34
Q

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

A

purine; pyrimidine; deoxyribose backbone

35
Q

most extensively studied DNA lesion is ____

A

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

36
Q

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

A

mutagenesis; carcinogenesis; aging

37
Q

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

A

amino acid; cysteine; methionine

38
Q

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

A

thyroid gland; iodine atoms; thyroglobulin

39
Q

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

A

macrophages; neutrophils

40
Q

defense mechanisms against free radical -induced oxidative stress involve:

A
  • preventive mechanisms
  • repair mechanisms
  • physical defenses
41
Q

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

A

enzymatic

42
Q

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

A

superoxide dismutase (SOD)

43
Q

___ converts hydrogen peroxide to water and oxygen

A

catalase

44
Q

small molecules that are antioxidant

A

vitamins A, C, and E and uric acid

45
Q

diseases developed by ROS

A

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

Biochem (14 decks)

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