The Nitrogen Cycle

My AP Biology Thoughts Episode #37 Nitrogen Cycle

Welcome to My AP Biology Thoughts podcast, my name is Sid and I am your host for episode #37 called Unit #1 Chemistry of Life: Nitrogen Cycle.

Segment 1: Introduction to the Nitrogen Cycle

The nitrogen cycle is a complex cycle that circulates nitrogen on Earth. Nitrogen is extremely important for life because it plays roles in the production of proteins and nucleic acids. Because of this it is essential for all life. On earth, 78 percent of the atmosphere is nitrogen. Despite this abundance, most organisms are unable to use nitrogen in the form of gas. This is where the nitrogen cycle comes in. The steps of the nitrogen cycle are nitrogen fixation, nitrogen assimilation, ammonification, nitrification, and denitrification. Because this is cyclical, there is no real “first” step to the nitrogen cycle. Instead, the nitrogen is continuously cycling in through its various forms. Nitrogen first gets into the soil by precipitation. The water carries nitrogen into the soil. The nitrogen then finds its way to the bacteria that live on the roots of plants. Then the nitrogen is combined with hydrogen at the roots to make ammonium. This process is called nitrogen fixation. This can also be done by lightning in the atmosphere. After the nitrogen has become a part of ammonium, nitrifying bacteria add oxygen in order to create nitrites. This process is called nitrification. Unlike ammonium, the nitrites are not toxic. After this, once again more nitrifying bacteria come in and turn the nitrites into nitrates. After this process, the plants can finally absorb the nitrates. The process of plants absorbing the nitrates is called assimilation. Still, all of the nitrates are not used for plants. Some of the nitrates can go to denitrifying bacteria which turn the nitrates back into the atmosphere. This process is called denitrifying. Also, after the plants have absorbed the nitrates, then animals eat the plants with nitrogen in them in order to get nitrogen. Once the animals leave waste or die, the get broken down by decomposers which allow for ammonification to occur once again where the nitrogen can go back into the cycle as ammonium.

Segment 2: Example of Nitrogen Cycle

Now we can look at how specific plants and animals use nitrogen or are a part of the nitrogen cycle. Simple examples of this can come from primary consumers which take the nitrogen directly from the plants. For example, rabbits are primary consumers who get their energy from plants. From plants, they also get nitrogen. A rabbit might eat plants like lettuce, beans, broccoli, and even some flowers. All of these plants, in order to live, will have nitrogen in their cells. After the rabbit eats one of these plants, the nitrogen gets transferred into their system. Then they can use the nitrogen for proteins or nucleic acids which are essential to their survival.

Another specific exam can be of humans. Humans eat plants and animals frequently. Nitrogen comes from both of these food sources. When humans eat vegetables, the vegetables were once plants that absorbed nitrogen through the soil. Then when we eat the plants, we absorb that nitrogen. Also, when humans eat meat, the animal had at one point eaten plants with nitrogen in them which allowed them to have nitrogen. Then we absorb that nitrogen from the animal.

Segment 3: Digging Deeper Into the Nitrogen Cycle

Nitrogen is extremely important for all living things. This is because nitrogen is involved in many essential processes. For this reason, the nitrogen cycle has a big part to play in the chemistry of life. Specifically, out of the four macromolecules, nitrogen is involved in the formation of proteins and amino acids. Proteins are arguably the most important macromolecule as they serve a variety of functions such as in the...