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level: STABLE HYDROGEN ISOTOPES

Questions and Answers List

level questions: STABLE HYDROGEN ISOTOPES

QuestionAnswer
What are the two stable isotopes of hydrogen making of the dD?protium (1H) and deuterium (2H, D). -->deuterium has one proton, one neutron and one electron
dD is measured against?SMOW (Standard Mean Ocean Water) and SLAP (Standard Light Antarctic Precipitation)
dD has a much larer range than d13C because?because of the larger mass difference
Clouds are ... in deuteriumdepleted (due to the evaporatio-precipitation balance and fractoination)
Rain is ... compared to the cloudenriched (heavier will rain out first, leaving the cloud more depleted)
The more inland or the higher the altitude the more ..... your dD becomesdepleted
Bulk organic matter contains a lot of exchangeable hydrogen, hence we need to anaylse strongly (covalently) bound hydrogen. Where do we find these?lipids
Largest step in hydrogen isotopic fractionation in organisms is by formation of .... and estimated to be ca. 171 per millNADPH - but internally there is more fractionation taking place, but it is hard for us to know which enxymes/pathways are responsible
If you make a lipid you will be .... in comparison to total biomass (with some exceptions!)depleted
Hydrogen isotopic fractionation of lipids is depending on carbon/energy metabolism and can help us determine ..?if it is a chemautotroph or photo(auto/hetero)troph
hydrogen isotopic fractionation in plants: Lipid classes have different hydrogen isotopic compositions (but differently from 13C), name the patternn-alkanoic acids least depleted, then sterol, then lastly phytols (compared to water!) -> compared to bulk: phytols least depleted and then n-alkanoic&sterols
Straight chain compounds are more ... than isoprenoid compoundsenriched (n-alkanoic acids vs phytols)
Differences in hydrogen isotopic composition between isoprenoid lipids due to different ...biosynthethic pathways
Where it is synthesised in the cell determines ....the starting pool of hydrogen isotopes
hydrogenation of doublebonds during biosynhtesis leads to ... in dDincreasing depletion
dD of n-alkanes (from plants) mostly reflects ...precipitation/evaporation balance because this affects the dD of the source water
influences on dD of terrestrial n-alkanessource water dD(precip/evap), fractionation due to biosynthesis of lipids and minorly by C3/C4 metabolism
hydrogen isotopes reflect the input of freshwater through rivers and throught that also correlates with ...?salinity
there is no large impact of ... on hydrogen isotopic fractonationtemperatures -> but there is of salinity
lower dD = ?more rain out(wet climate)/fresh water
hydrogen fractionation is impacted by lightmore fractionation at light optimum
The hydrogen isotopic composition of lipids from aquatic organisms is influenced by the following major factors:- Metabolism of organisms - Biosynthesis lipids - dD of the source water - Salinity – in marine environment - Light – we like to ignore this - Only minor effect of growth rate/nutrients