Nitrates (SQA National 5 Biology): Revision Note

Nitrates

• Nitrates can be defined as:

nitrogen-containing mineral ions (NO₃^-), dissolved in soil water, that are available for uptake by plant roots

• Nitrogen-containing compounds are transferred through ecosystems as follows:

  1. Nitrates dissolved in soil water are absorbed by plants

  2. Nitrates are converted into amino acids inside plant cells and used to build plant proteins during protein synthesis

  3. Animals consume plants and digest the proteins present in their tissues

  4. Amino acids from protein digestion are built up into new animal proteins, which are available for consumption to the next level of the food chain

  5. At any point, nitrogen may return to the soil as a result of excretion or death, followed by decomposition

• Soils can become nitrate-deficient due to crop harvesting or leaching, so fertilisers can be added to the soil to increase its nitrate content