Nutrient Cycles Flashcards
Describe how the action of microorganisms in the soil produces a source of nitrates for crop plants (5)
- Protein converted into ammonia
- By saprobionts
- Ammonia into nitrite
- Nitrite into nitrate
- By nitrifying bacteria
- Nitrogen gas to ammonia
- By nitrogen fixing bacteria
Describe nitrification (2)
- Ammonia to nitrites to nitrates
- By nitrifying bacteria
Describe denitrification (2)
- Nitrates to nitrogen gas
- By denitrifying bacteria
Describe nitrogen fixation (2)
- Nitrogen gas to ammonia
- By nitrogen fixing bacteria
- Describe ammonification/decomposition (2)
- Nitrogen containing compounds to ammonia
- By saprobiants
Describe the phosphorus cycle (5)
- Phospholipids, RNA and DNA from dead organisms into phosphate ions
- Decomposed by saprobionts
- Phosphate ions also found in waste and remains
- Phosphate ions transported by lakes
- Form sedimentary rock
- Weathering and erosion of rocks helps phosphate ions dissolve in lakes
- Phosphates become available for absorption by plants to incorporate into biomass
Explain what is meant by the term carbon sink. (2)
- Takes up / stores carbon dioxide
- Named example e.g. peat / coal / limestone / trees / fossil fuel / chalk / shells ;
Explain what is meant by the term global warming. (5)
- Increase in temperature of earth’s surface
- Due to an increase in greenhouse gases
- Which reflect back heat in the atmosphere
- So increased greenhouse effect
- Causing … melting ice caps, flooding, climate change
Describe the role of saprobionts in the nitrogen cycle. (2)
- Decompose proteins
- Produces ammonia
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. (5)
- extracellular digestion
- by secretion of enzymes;
- absorption of digested 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. (6)
- Proteins broken down
- Ammonification
- By saprobionts
- Nitrites to nitrates
- By nitrifying bacteria
- 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. (2)
- Very little ammonia
- Avoids use of decimal places / numbers become more manageable
- Allow comparisons
Give two examples of biological molecules containing nitrogen that would be removed when a crop is harvested.
- Amino acid/protein
- Nucleotide
- DNA
- RNA / mRNA / tRNA
- ATP/ADP
- NAD/NADP
- 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. (4)
- 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 (4)
- Make ATP so less energy for growth
- Make nucleotides so less DNA for cell division
- Make RuBP so less CO2 fixed
- Make phospholipids for membranes
