The Carbon and Nitrogen Cycles Flashcards
Topic-7
what are the 2 processes in which carbon is recycled and how?
-photosynthesis and respiration
-in photosynthesis producers fix carbon dioxide to produce a range of organic products
-in respiration these organic products and broken down to give ATP and give off carbon dioxide as a waste product
how do consumers gain carbon?
-through feeding as plant and animal tissue is rich in carbon
what is the role of saprobiotic microorganisms in the release of carbon?
-these decomposers break down dead organic molecules
-through decay and decomposition
-they release carbon and carbon dioxide through respiration
what does fossilisation mean?
-at certain stages of the earth’s history some dead organisms have been preserved in environments which do not decay
what does combustion mean?
-the release of carbon from fossil fuels
look at the diagram of the carbon cycle
-be able to draw it out
what are the 2 reasons for the recent increase in carbon dioxide levels in the atmosphere?
-increased combustion of fossil fuels
-deforestation
what are three compounds which are essential for life which contain nitrogen?
-proteins
-nitrogenous bases
-ATP
how does nitrogen enter plants? how is this nitrogen then used?
-it enters as nitrate ions which are absorbed from the soil through active transport
-the nitrate is used to build nitrogen containing compounds e.g. amino acids
what is the chemical symbol for nitrate?
-NO3
after the nitrogen is taken up by plants, how does it enter animals? what are the 2 ways nitrogen compounds removed from animals?
-plants are eaten by animals, these contain nitrogen
-eventually these compounds are excreted in faeces or end up as non living matter following death of the animal
what is the process of mineralisation in the recycling of nitrogen? what form is the nitrogen in?
-decomposition by the saprophytic bacteria allows for nitrogen from dead organic matter to be recycled
-it converted it to its usable inorganic form nitrate
what is the process of ammonification?
-this is the end of decay/ mineralisation
-it results in the production of ammonium ions from the decomposition of dead organic matter/ faeces
what is the process of nitrification? what are the two stages and what bacteria is used to carry them out?
-the conversion of ammonium ions to nitrate ions
-nitrifying bacteria
-first stage ammonium ions are oxidised to form nitrite ions
-a different genus of the bacteria then oxidises the nitrite to nitrate
what is the chemical symbol of nitrite?
-NO2
does nitrifying bacteria work aerobic or anaerobically? what is the result of the nitrifying bacteria producing nitrates?
-they need oxygen as oxidation reactions are involved
-the nitrate produced by the bacteria are absorbed in the soil by plants and the cycle continues
what are two other important processes involved in the nitrogen cycle?
-nitrogen fixation
-denitrification
what is the process of nitrogen fixation?
-nitrogen fixing bacteria convert nitrogen gas into nitrogen containing compounds
what is the enzyme nitrogen fixing bacteria contain and do they work aerobically or anaerobically?
-contain nitrogenase
-can be aerobic or anaerobic
what way can nitrogen fixing bacteria be found? what is an example of a plant which contains high amounts of this bacteria and what is the benefit of this?
-it can be free living or form mutual relationships
-legumes have high amounts of the bacteria which helps to enrich the soil with nitrogen
what is another way that nitrogen fixing can occur which doesn’t involve the bacteria? what is the process of this?
-through the process of lightning
-lightning breaks bonds between atmospheric nitrogen
-these combine with oxygen forming nitrogen oxides
-they dissolve in rain forming nitrates
what is the process of denitrification? what is the effect of this on soil?
-denitrifying bacteria convert nitrates into atmospheric nitrogen
-it reduces soil fertility
