Lesson 5.4 - Nitrogen Cycle: Part 1

Almost 80% of the atmosphere is nitrogen gas.  Nitrogen is an important element that living things need to make proteins and nucleic acids. 

The problem is that living things cannot use nitrogen gas as it exists in the atmosphere.  Only plants and organisms that make their own food can use nitrogen in the form of nitrates to make new cells.  All other organisms obtain their nitrogen from the organisms they eat.  

The nitrogen cycle is very complex.  We begin the study of the nitrogen cycle by explaining nitrogen and nitrates and how they are made. Nitrogen gas in the air is N2(g).  Nitrates are compounds that contain NO3- charged particles, which is the form that plants can use. 

Nitrogen from the atmosphere must react with oxygen to produce nitrates. Lightning causes the reaction between nitrogen and oxygen to produce nitrates.  These dissolve in the rain and fall to Earth.  The nitrate-containing rain water is absorbed by the roots of plants.  The plants use the nitrates to make their cells.

Now, answer the following questions.

 

Question 1. What is the difference between nitrogen gas and nitrates?

Question 2. What form must nitrogen be in before plants can use it to make cells?

Question 3. What natural occurrence produces nitrates in the atmosphere?

Question 4. How do the nitrates produced in the atmosphere by lightning get to the plants?

 

Check your answers with those that follow.

 

 

 

 

 

 

 

 

 

 

 

 

Answers to Questions:

Question 1. What is the difference between nitrogen gas and nitrates?

Nitrogen gas is N2(g).  Nitrates contain nitrogen and oxygen and are charged particles.

Question 2. What form must nitrogen be in before plants can use it to make cells? 

Nitrogen must be in the form of nitrates before plants can use it to make cells.

Question 3. What natural occurrence produces nitrates in the atmosphere?

Lightning produces nitrates in the atmosphere.

Question 4. How do the nitrates produced in the atmosphere by lightning get to the plants?

The nitrates are produced by lightning dissolve in rainwater; the rainwater is absorbed by the plant roots. 

 


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