lec 16 Flashcards

1
Q

in the presence of oxygen, how does Fe3+ behave? when oxygen is not available, what happens? [REVIEW]

A

in oxygen, Fe3+ forms insoluble oxides
in anoxia, Fe3+ is reduced to Fe2+ which will come together with sulfur (returns to Fe3+ when oxygen returns)

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2
Q

how do iron, sulfur, and phosphorus come together?

A

in the oxygenated water column, Fe3+ combines w orthophosphate and falls into anoxic sediments. at that point, Fe3+ is reduced to Fe2+, releasing the orthophosphate and picking up a sulfur instead to form pyrite

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3
Q

what is the difference between natural and cultural eutrophication?

A

natural eutrophication occurs naturally w the ebb and flow of nutrients. cultural eutrophication occurs specifically due to anthropogenic inputs

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4
Q

looking at irl examples, chlorophyll a, canthaxanthin, and zeaxanthin are important to note. what do they indicate?

A

chlorophyll a is a general indicator of cyanobacteria, while canthaxanthin indicates nuisance cyanobacteria and zeaxanthin indicates other cyanobacteria!

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5
Q

what happens to hydrogen sulfide in different pH conditions?

A

in acidic conditions turns into a gas, in basic conditions turns into S2- ions (protons get neutralized so ur left w the anions)

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6
Q

sulfur + O2 = ? how have bacteria adapted this ?

A

sulfur can become OXIDIZED in the presence of oxygen (REDOX) for a huge release of potential energy - some bacteria use sulfur for chemosynthesis

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7
Q

what is the process of Sulfur disproportionation?

A

thiosulfate –> sulfate –> sulfides under anoxic conditions to prod energy

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8
Q

pyrite has low solubility, which can be bad for locking up iron in aq ecosystems. certain bacteria can be used to free up this iron, but there is a drawback. what is it?

A

the process produces a lot of sulfuric acid which, if returned to the aq ecosystem, can acidify an environment or result in things like acid rain

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9
Q

some bacteria have adapted to use sulfur, such as Beggiatoa. tell me what those funky dudes do

A

store nitrates in oxic areas, then travel to anoxic sediments that are rich in sulfur. nitrates are oxidized, releasing lots of energy

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10
Q

what is anoxygenic photosynthesis?

A

a form of photosynthesis where sulfate is broken up for oxygen instead of water :)

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11
Q

iron is very important in many process (list 3)

A

key element in ETC prot, hemoglobin, a bunch of enzymes

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12
Q

what is the difference between ferric and ferrous iron? where can either be found?

A

ferric iron is Fe3+, and is found in oxic conditions. ferric iron gives electrons (gets oxidized easily)
ferrous iron is Fe2+ and is found in anoxic conditions. ferrous iron accepts electrons (gets reduced easily)

can think of ferrous as ferr-US (us being 2 people :D)

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13
Q

what are chelators? what are organic instances of them?

A

chelator is a type of bonding. organisms maintain high conc of iron in oxic environ by briefly binding iron to prevent it from turning into precipitates like ferric hydroxide

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14
Q

dystopic wetlands are unproductive because a lack of light, but iron might also play a role. what is this role?

A

humic material (that dead/decomposing shit) can complex with iron, such that organisms are unable to use it. if enough humic material is around, no iron is left available –> nothing can survive

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15
Q

is it ferric or ferrous iron that precipitates phosphorus?

A

ferric (Fe3+) iron - the dude in the oxic environment

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