Absorb nitrate and build plant proteins
Plants absorb nitrate ions and use their nitrogen to make amino acids and proteins.
Extended only (Supplement); Biology 0610, 2026–2028. Use the stated specimen features and evidence. Diagrams are schematic. Written practice is self-checked
Before you begin
- Use the food-web pathway and distinguish matter cycling from energy flow.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
What nitrogen-containing soil ion do plants absorb in this syllabus route?
What you will learn
- Trace nitrate ions into plants
- Connect nitrate uptake with amino-acid and protein production
Plants take up nitrate ions
Plant roots absorb nitrate ions from the soil solution. Nitrate supplies nitrogen that can be incorporated into amino acids; amino acids are then joined to make plant proteins. This transfers nitrogen from inorganic soil compounds into organic plant material.
Do not say plants absorb proteins from soil and turn them into plant protein. The route in the syllabus is uptake of nitrate ions, followed by production of amino acids and proteins.
Connect the plant step to feeding
When an animal eats a plant, nitrogen in plant proteins can transfer into the animal. Dead plant material and waste later provide protein for decomposition. Plants do not absorb nitrogen gas directly from the atmosphere in this route; fixation processes first make nitrogen compounds.
Keep the sequence: fixation and nitrification supply soil nitrate, plant uptake brings nitrate into the plant, and amino-acid/protein production incorporates its nitrogen.
Pause and explain
What products are made from absorbed nitrate nitrogen?
Worked example
A plant absorbs nitrate from soil. Describe the next two nitrogen-containing products named in the syllabus.
Show the worked solution
- Nitrate is absorbed by the plant.
- Nitrogen is used to produce amino acids.
- Amino acids are joined into proteins.
Answer The plant uses absorbed nitrate nitrogen to produce amino acids and then proteins.
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Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Complete the plant pathway: soil nitrate → plant → ____ → ____.
Give me a hint
Name the organic molecules in order.
Compare my reasoning
- Nitrate nitrogen is used to make amino acids.
- Amino acids are joined into proteins.
Soil nitrate ions → plant amino acids → plant proteins.
Look for these in your work
- Amino acid intermediate
- Protein product
Correct the sentence “Plants get protein by absorbing it from nitrate in the soil.”
Give me a hint
Separate ion uptake from protein synthesis.
Compare my reasoning
- Plants absorb nitrate ions.
- They use nitrate nitrogen to make amino acids and proteins.
Plants absorb nitrate ions from the soil and use the nitrogen to produce amino acids and proteins; they do not absorb protein from nitrate.
Look for these in your work
- Uptake corrected
- Synthesis described
A plant has absorbed nitrate ions. How can that nitrogen later reach a herbivore?
Give me a hint
Follow the food link.
Compare my reasoning
- The plant incorporates nitrogen into proteins.
- The herbivore feeds on the plant.
The plant uses nitrate nitrogen to make amino acids and proteins; feeding transfers that protein nitrogen to the herbivore.
Look for these in your work
- Plant incorporation included
- Feeding transfer stated
Common mistakes
- Saying plants absorb nitrate-containing proteins
- Skipping amino acids
- Saying plant roots absorb N₂ gas directly
What can you explain now?
What nitrogen-containing soil ion do plants absorb in this syllabus route?
Compare with the explanation
Nitrate ions
The plant uptake step is nitrate absorption.
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Make it stick
Trace nitrogen from nitrate ions in soil into a plant protein.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.