Lecture 11 Flashcards
All nutrient cycles are linked to the _______ cycle, but nitrogen is very closely linked because nitrogen and _____ are ________.
Carbon, Carbon, macronutirents
While the ______ and rocks in the Earth’s crust are the
largest carbon reservoir, CO2 in the atmosphere is the _____
_____ _____ carbon reservoir.
sediments, most rapidly transferred
CO2 is removed from the atmosphere by ________ land
plants and marine microbes, so a large amount of carbon is
found there.
photosynthetic
More carbon is found in humus, or _____ organic material, than is found in the living organisms in a region.
dead
CO2 is returned to the atmosphere by _______ and ________ as well as by human-related (anthropogenic) activities.
respiration, decomposition
Photosynthesis
CO2 + H2O (CH2O) + O2
Respiration
(CH2O) + O2 CO2 + H2O
The two major end products of decomposition are ____ and _____.
methane (CH4) and carbon dioxide (CO2 ).
form when high levels of methane are under high pressure and low temperature
Methane hydrates
Methane hydrates fuel deep-sea ecosystems called
cold seeps
_______ is central to carbon cycling in anoxic environments.
Methanogenesis
Most ______ use carbon dioxide as a terminal electron acceptor, reducing CO2 to CH4 with H2 as an electron donor; some can reduce other substrates (e.g., acetate) to form CH4.
methanogens
Methanogens team up with partners (______) that supply them with necessary substrates.
syntrophs
Nitrogen exists in a number of ____ states.
oxidation
Four major nitrogen transformations
- nitrification
- denitrificatoin
- anammox
- nitrogen fixation
N2 is abundant but not _____ ______
biologically available
Nitrogen fixatoin is only done by_____
bacteria
_____ is the anaerobic oxidation of ammonia to N2 gas.
Anammox
________ and ______ result in losses of organic nitrogen from the biosphere.
Denitrification and anammox
The _____ process is dependent on natural gas
Haber process
slide 15, 16,
Nitrogen fixaton has ___ round of reduction per N2.
4
____ _____ consumed for each N2 fixed
40 ATPs
Anaerobic ______ make NH3
heterocysts
Glutamine donates NH3 to make other amino acids
Transamination
The steps of nitrogen fixation
- slide 17
2.
3.
4.
Incorporation of NH4+ into amino acids
Nitrogen assimilation
2nd species oxidizes NO2- to NO3-
Nitrobacter
species oxidizes NH4+ to NO2-
Nitrosomas
_____ of streams comes from excess nutrients and growth
Eutrophication
NO3- -> NO2- -> NO -> N2O -> N2
Dissimilatory nitrate reduction
The bulk of sulfur on Earth occurs in sediments and rocks as ___ and ____ minerals (e.g., gypsum, pyrite).
sulfate and sulfide
The ___ represent the most significant reservoir of sulfur (as sulfate) in the biosphere.
oceans
slide 23 pic, memorize
flide 12 pic memorize
is a major volatile sulfur gas that is produced by bacteria via sulfate reduction or emitted from geochemical sources.
Hydrogen sulfide
is toxic to many plants and animals and reacts with numerous metals.
Sulfide
The most abundant organic sulfur compound in nature is ____ _____.
dimethyl sulfide (DMS).
On Earth’s surface, iron exists naturally in two oxidation states.
ferrous (Fe2+) and ferric (Fe3+).
____ is soluble but tends to rust (______) and become _____, which is not soluble.
Ferrous (2+), oxidize, ferric (3+)
Memorize slide 27 pic cycle
Phosphorus is a typical ____ ____ that limits the growth of aquatic photosynthetic autotrophs.
limiting nutrient
Calcium cycle _____ are rocks and oceans
reservoirs
The marine silica cycle is controlled by unicellular eukaryotes that build cell skeletons called ______.
frustules
Examples of frustules
- diatoms
- silicoflagellates
- radiolarians
Mercury is not harmful, but ____ ___ is. It is dangerous because it can _________.
mythyl mercury, bioaccumulate
