Respiratory Processes Defined by Electron Acceptor Flashcards
What is denitrification?
Denitrification is the process by which nitrate is reduced to nitrogen gas or other nitrogenous gases.
What are two ways in which nitrate is reduced that do not result in denitrification?
Nitrate can be reduced to nitrite or ammonium without resulting in denitrification.
Why is denitrification detrimental to agriculture?
Denitrification can lead to the loss of nitrogen from the soil, which is essential for plant growth.
How does denitrification affect the environment?
Denitrification can contribute to the release of nitrogen gases into the atmosphere, impacting climate change.
How can denitrification be beneficial?
Denitrification can help remove excess nitrates from water bodies, reducing eutrophication.
What enzyme is required for the first step of dissimilative nitrate reduction? What unusual metal does it contain?
The enzyme required is nitrate reductase, which contains molybdenum.
What two conditions must exist for the enzyme nitrate reductase to be produced?
The presence of nitrate and an anaerobic environment are required for the production of nitrate reductase.
What three additional enzymes are involved in denitrification? What are their substrates and products?
The three additional enzymes are nitrite reductase (substrate: nitrite, product: nitric oxide), nitric oxide reductase (substrate: nitric oxide, product: nitrous oxide), and nitrous oxide reductase (substrate: nitrous oxide, product: nitrogen gas).
What are some examples of inorganic sulfur compounds that can serve as electron acceptors in anaerobic respiration?
Examples include sulfate, thiosulfate, and sulfite.
What is the difference between assimilative and dissimilative sulfate metabolism?
Assimilative sulfate metabolism incorporates sulfate into organic compounds, while dissimilative sulfate metabolism reduces sulfate to sulfide without incorporation into biomass. Dissimilative metabolism can be performed by most microbes.
Why are sulfate-reducing prokaryotes limited to oxidizing only certain electron donors?
Sulfate-reducing prokaryotes are limited due to their specific metabolic pathways and the energy yield from certain electron donors.
What electron donor is used by virtually all sulfate-reducing prokaryotes?
Virtually all sulfate-reducing prokaryotes use organic compounds as electron donors.
How many electrons are required to reduce sulfate to hydrogen sulfide?
Eight electrons are required to reduce sulfate to hydrogen sulfide.
Why must sulfate be activated by ATP before it can be reduced?
Sulfate must be activated by ATP to form adenosine phosphosulfate (APS), which is a necessary intermediate for reduction.
What are the intermediates that are formed during dissimilative sulfate reduction? What enzymes are used?
Intermediates include adenosine phosphosulfate (APS) and sulfite, with enzymes such as sulfate adenylyltransferase and sulfite reductase being used.
What are the intermediates that are formed during assimilative sulfate reduction? What enzymes are used?
Intermediates include cysteine and other organic sulfur compounds, with enzymes such as sulfate adenylyltransferase and cysteine synthase being used.
Why must sulfate-reducing prokaryotes possess hydrogenase?
Sulfate-reducing prokaryotes must possess hydrogenase to utilize hydrogen as an electron donor.
What advantage do organotrophic sulfate-reducers have over strictly lithotrophic sulfate-reducers?
Organotrophic sulfate-reducers can utilize a wider range of organic substrates for energy compared to strictly lithotrophic sulfate-reducers.
What is disproportionation and why is it important to sulfate-reducers?
Disproportionation is the process where a compound is simultaneously oxidized and reduced. It is important for sulfate-reducers as it allows them to utilize sulfur compounds effectively.
How is sulfur reduction different from sulfate reduction?
Sulfur reduction involves the reduction of elemental sulfur to sulfide, while sulfate reduction involves the reduction of sulfate to sulfide.
What electron donors can be used by sulfur-reducers?
Sulfur-reducers can use hydrogen, organic compounds, and certain metals as electron donors.
What are the two most important metal ions that can serve as electron acceptors in anaerobic respiration?
The two most important metal ions are iron (Fe) and manganese (Mn).
What are three metalloids that can serve as electron acceptors in anaerobic respiration?
Three metalloids that can serve as electron acceptors are arsenic, selenium, and tellurium.
What is biomineralization? Give an example.
Biomineralization is the process by which living organisms produce minerals. An example is the formation of calcium carbonate shells by marine organisms.
