The Journey of a Carbon Atom

The Journey of a Carbon Atom

Through Photosynthesis and Fermentation

Fermentation: Lactic Acid

Before Carl gets to the actual fermentation process he has to go through Glcolysis. Glycolysis breaks down Carl's six-carbon glucose molecule into three-carbon molecules called pyruvate. Glycolysis also uses two ATP molecules, but ends up producing four.

Now for Fermentation

The In-Between

Now that Carl has undergone Glycolysis he can begin the fermentation process. Fermentation is a form anaerobic respiration, a process that occurs with no oxygen. Fermentation produces significantly fewer ATP molecules than cellular respiration.

Lactic acid fermentation takes two pyruvate molecules and converts them into lactic acid. When the human was exercising her muscles used oxygen faster than her breathing could replenish it. Build-up of lactic acid causes the muscles to hurt, but the lactic acid is eventually carried away to the liver where it is conveted into pyruvate again.

Carl, stored as glucose, is eaten by a human being just like you! The human then goes to the gym...where they will exercise. Carl's in for another wild ride.

For each glucose molecule that fermentation uses, only two ATP molecules are produced. Fermentation also replenished the supply of NAD+ for use in Glycolysis.

Oh boy another adventure!

Light-Independent reactions

Today I started out as part of a Carbon-dioxide atom and through photosynthesis a plant made me into Glucose for it to eat, only to get eaten! I wonder how this human is going to use me...

Now here's where I com in!

While the light-dependent reactions have been taking place on the other side of the cell, Carl's carbon dioxide molecule -- along with five other carbon dioxide molecules, have been entering the cycle one at a time. An enzyme in the stroma combines the carbon-dioxide molecule with other carbon-based molecules that are already present within the organelle. This forms the three-carbon molecule that continues the cycle.

Fun fact, light-independent reactions are sometimes called the Calvin cycle, after the scientist that discovered the pathways of photosynthesis. His name was Melvin Calvin.

For every six carbon-dioxide molecules that enter the cycle, 12 three carbon molecules are formed. The three-carbon molecules undergo a series of reaction that break them down, removing some of the atoms bonded to them. These reactions are powered by the ATP and NADPH molecules from the light-dependent reactions. The three-carbon atoms that have been transformed still contain a three-carbon chain, but other atoms in the molecule have changed.

Light-Dependent reactions

For every 12 three-carbon molecules that are formed, two are removed to build organic compounds such as six-carbon sugar such as glucose. The remaining ten molecules continue on in the cycle.

The light-dependent reactions occur in the thylakoids. Chlorophyll molecules absorb sunlight and then give off high-energy electrons, which move through a series of electron carrier proteins, aptly called the electron transport chains.

Glucose and other carbohydrates are used for long time energy storage.

The proteins within the electron transport chains use the energy of the electrons to pump hydrogen ions into the thylakoid from the surrounding stroma, (stroma is the gel-like substance inside the chloroplast). The hydrogen ions that are pumped in begin to build up in the thylakoid.

Now that there is a build-up of hydrogen ions in the thylakoids, they want to move back to an area of low concentration, the stroma, through diffusion. The hydrogen ions move back into the stroma through a protein channel called ATP synthesis. As the hydrogen ions move through this channel, they bond a phosphate group to an ADP molecule to form an ATP molecule.

Now something interesting is happening back in the electron transport chains. The high-energy electrons have reached the end of the electron transport chain and have met up with some NADP+ molecules. Together high-energy electrons, NADP+ molecules, and hydrogen ions from NADPH molecules that carry the high energy electrons to the next stage of photosynthesis.

The Begging

In order to continue these reactions the electrons and hydrogen ions must be replaced. An enzyme that splits water removes electrons from the water molecule and puts them in the chlorophyll molecules. At the same time this splits apart the oxygen molecules and the hydrogen ions. The hydrogen ions, like the electrons, return to the chloroplast while the oxygen is released into the air.

It all started on a sunny day. I was floating around when all of a sudden...

Carl's Carbon Dioxide Atom was sucked into a Chloroplast Organelle! These are the plant cells responsible for making a plant's food.

The Star: Carbon Atom

Now Carl is to participate in the Light-Dependent reactions, and the Light-Independent reactions.

Greetings Human! I am Carbon Atom, but you can call me Carl for short. Today I shall guide you through an eventful day in my life.

We will follow Carl as he partakes in the process of Photosynthesis and Fermentation. As you will all find out. Carl is an important atom.

Image Credits

http://itc.gsw.edu/faculty/speavy/spclass/chemistry/atoms.htm

http://www.nature.com/scitable/topicpage/plant-cells-chloroplasts-and-cell-walls-14053956

http://cnx.org/content/m45452/latest/?collection=col11487/latest

https://benchprep.com/blog/ap-biology-photosynthesis-3-light-independent-reaction/

http://monalux.deviantart.com/art/Food-Poses-5-372983643

http://www2.estrellamountain.edu/faculty/farabee/biobk/biobookglyc.html