Nutrient Cycles Flashcards
Which microorganism undergoes nitrification?
Nitrifying bacteria
Which microorganism undergoes denitrification?
Denitrifying bacteria
What is the reaction for nitrogen fixation
Nitrogen gas to ammonia (reduction)
What is Nitrification
Conversion of ammonium ions to nitrite ions (NO2-) and then nitrate ions (NO3-) in the soil
NH4+ ions —> NO2 - ions —> NO3 - ions
What is Rhizobia
A bacterium found in the root nodules of legumes (undergo nitrogen fixation)
What is Ammonification
Decomposition of dead organisms which releases ammonia or ammonium ions into the soil
Organic nitrogen (e.g. DNA, RNA, proteins etc.) —> NH4+ ions
What is Nitrogen fixation
The conversion of atmospheric nitrogen to nitrogen compounds such as ammonia
N2 gas —> NH3 / NH4+ ions
What is Denitrifcation
The conversion of nitrates back to nitrogen gas. (Waterlogged soil, Anaerobic conditions - Pseudomonas denitrifying bacteria)
NO3 - ions —> N2 gas
Explain what is meant by the term carbon sink.
- Takes up / locks up / stores carbon / carbon dioxide (for a long time) / eq ;
- Named example e.g. peat / coal / limestone / trees / fossil fuel / chalk / shells ;
Explain what is meant by the term global warming.
- Increase in {temperature of earth’s surface / mean global temperature / eq};
- Carbon dioxide is a greenhouse gas / due to an increase in greenhouse gases ;
- (Which) {trap / reflect back} {heat / long wave / infra red} (in the atmosphere) ;
- Reference to an {increased / enhanced} greenhouse effect ;
- Reference to valid {effect / consequence} e.g. melting ice caps, flooding, climate
- change ;
Describe the role of saprobionts in the nitrogen cycle.
- (use enzymes to) decompose proteins / DNA / RNA / urea;
- Producing / releasing ammonia / ammonium ions;
Explain how carbon-containing compounds present in the pine leaves that fall from the trees are absorbed and used for growth by saprobionts/fungi that live in the soil.
- extracellular digestion;
- by secretion of enzymes;
- absorption of digested/soluble products;
- synthesis of structural compounds/named compound;.
- respiration provide energy for growth
Nitrogen compounds in the plants are made available for the main crop after ploughing in spring.
Describe the role of microorganisms in this process.
- proteins/amino acids broken down;
- deamination/ammonification/ release of ammonium compounds;
- By saprophytes/saprobionts/decomposers;
- conversion to nitrates via nitrites;
- by nitrifying bacteria/named bacterium;
- nitrates absorbed into roots via active transport
The scientists used units of μg g−1 for the concentration of ammonia in soil.
Suggest why, in this investigation, the scientists used these units.
- (μg because) very little ammonia (in soil);
- (μg because) avoids use of (lots of) decimal places (in their results) / avoids the use of powers of 10 / avoids the use of standard form /makes numbers more manageable / Accept makes easier to plot graph
- (g-1) to allow comparisons (between samples);
Give two examples of biological molecules containing nitrogen that would be removed when a crop is harvested.
- amino acid/protein/ polypeptide/peptide;
- nucleic acid/nucleotide/base;
- DNA;
- RNA / pre-mRNA / mRNA / rRNA / tRNA
- ATP/ADP;
- NAD/NADP (reduced or not);
- Cyclic AMP/cAMP;
- Chlorophyll;
Plants absorb a number of other nutrients from the soil including phosphates. Describe why phosphates are needed by a growing plant.
- production of phospholipids;
- in cell membranes;
- synthesis of ATP;
- production of DNA;
- production of RNA;
- production of NADP
Describe how a lack of phosphates in the soil surrounding a plant can affect its growth
- (Required to) make ATP/glucose phosphate, so less respiration/less energy for growth;
- (Required to) make nucleotides, so less DNA/mRNA/tRNA for cell division/production of protein (for growth);
- (Required to) make RuBP/NADP, so less CO2 fixed/reduced into sugar;
- (Required to) make phospholipids for membranes;
Outline the advantages of having Mycorrhizae
growth near plants
- Mycorrhizae help plants to defend themselves (causing an increase in crop yield);
- Mycorrhizae help plants to take up nitrates/phosphates (causing an increase in crop yield);
Describe the process of eutrophication.
- Nitrates / Phosphates / Ammonium ions flushed into waterway
- Increased algal bloom
- Light blocked out
- Submerged aquatic plant unable to photosynthesise and die
- Increase in saprobionts so increases rate of aerobic respiration
- Saprobionts / aero.resp organism die as lack of oxygen (anoxic)
- Increase in anaerobic microorganisms
- Production of toxins
