ch 14 Flashcards

1
Q

why are redox reactions important

A

bc the relocation of electrons rleleases energy

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2
Q

reduction potential

A

measures the ability of a species to attract an electron and be reduced

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3
Q

what is the reference for reduction potentials

A

SHE
standard hydrogen electrode

2H+ + 2e- = H2

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4
Q

electrons flow from _ to _

A

low reductino potential to high reductino potential

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5
Q

if E rxn is greater than 0, K is

A

greater than 1

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6
Q

gibbs free energy

A

the max amount of work that can be extracted from closed system at fixed t and pressure

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7
Q

electron activity

A

the degree to whcih electrons move from one species to another

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8
Q

how can we find E rxn in non standard conditions

A

use nernst equation

use E at ph 7 bc that is the ph of water

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9
Q

Ehw = Eh and what

A

minus 0.42

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10
Q

PEw= pe and what

A

minus 7

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11
Q

strongest oxidizing agent in seawater

A

o2

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12
Q

all biochemically active elements in oxic seawater will be

A

mainly in thier highest oxidation state

the most positive they can be

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13
Q

the redox rxn in seawater that produces the most E is

A

aerobic oxidation of organics

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14
Q

sulfide oxidizers

A

bact in the ocean that are in hydrothermal vents

use O2 and H2S and form SO420 and H+

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15
Q

largest formatino of E

A

aerobic respiration of organic matter

most important source of enrgy for heterotrophs

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16
Q

what are some anoxic enviroments

A

in the gut of animals

o2 min at pycnocline

sediments

17
Q

denitrification

A

Nitrate NO3- to N2

cant use this form of N
limits biological growth

18
Q

benifit of aerobic respiration

A

prevents sequesteration of C in POC and returns CO2 to water and dec pH and affects climate

19
Q

nitrate reduction

A

NO3- to NO2-

emission of nitrous oxide

potent greenhouse gas

20
Q

sulfate reduction

A

SO42- to H2S

toxic gas
kills most organisms
low o2
dead zones

20
Q

nitrogen fixation

A

H2 to NO3-

available N

20
Q

methane fermentation

A

convert organic mater to CO2 and CH4

both greenhouse gasses
trap heat

20
Q

iron reduction

A

fe3 to fe2

available and soluble form of iron

21
Q

what does nitrogen fixation

A

done by cyanobacteria and anaerobic bacteria

22
Q

what is reduced in aerobic respiration

A

o2

23
Q

why is organic matter the most importatn reducing agent

A

relatively abundant

has a low pE

24
Q

how is organic matter derived

A

directly or indirectly from biological fixation rxns where oxidized inorganic carbon CO2 is converted to reduced organic form CH2O

25
Q

E source names

A

photo- light
chemo - organic matter

26
Q

carbon source names

A

auto- inorganic
organo- organic carbon

27
Q

electron source names

A

litho- inoganic e donor
hetero - organic electron donor

28
Q

photoautolithotrophs example

A

phytoplankton that use H2O as electron source

green sulfur bact- use H2 or H2S or S as electron source

some use Fe2+

29
Q

strategies of chemoautolithotrophs

A

archaea and bact

oxidation of hydrogen
sulfur
reduced nitrogen
reduced metals

30
Q

methanogens

A

use H2 as source of electrons and CO2 as soruce of C and methanol as E

31
Q

supersaturations of methane in surface water suggest

A

methanogenesis occurs in anaerobic interiors of particles

32
Q

why is the production of methane important to understand

A

bc it is a potent greenhouse gas

33
Q

mixotrophs

A

use both organic matter and light as energy sources

hetero and photo

34
Q

mixotrophs example

A

phytoplankton and dinoglagellates and cyanobacteria

35
Q

what are some things nobody seems to be able to do

A

oxidze Mn2+ and N2

anoxygenic photosynth using NH3, PH3, CH4 as e- donors

36
Q
A