What is the process of carbon tracing from leaves?

Answer 1

Depending on the complexity of the course, and therefore of the answer, you may need to research the carbon cycle that occurs during photosynthesis, which is a many step chain of chemical reactions proceeding from the intake of carbon dioxide and water and leading to the output of oxygen and glucose.

A plant takes in water and also absorbs the carbon dioxide that we exhale.

H2O + CO2

The plant undergoes a series of processes which involves chemical structures in the leaf to transform these chemicals into glucose, which is absorbed by the plant to grow, and oxygen, which is released as waste essentially.

The balanced although incorrect equation would be,

H2O + CO2 -> O2 + CH2O

incorrect because glucose is in fact 6 carbons, not 1, so the structure would be C6H12O6, and then the equation would have to be rebalanced to

6H2O + 6CO2 -> 6O2 + C6H12O6

You can check that this is correct by counting the atoms on the left and right side and making sure they line up, namely

Hydrogen : 12 and 12

Oxygen: 6 + 12 and 12 + 6

Carbon: 6 and 6

So what is meant by Carbon tracing?

Well, as you can see above, Carbon enters the plant in the form of CO2, 6 of them in this case, to create glucose for the plant, C6H12O6. Carbon tracing may refer to the process by which 6 Carbon Dioxides (CO2) become glucose (C6H12O6).

As expected, there are numerous pathways within the chloroplast (where photosynthesis is carried out) that contribute to the chemical process of carbon dioxide becoming glucose.

In the first step, Carbon Dioxide is fixated to one of the plants 5 Carbon sugars called Ribulose 1,5-bisphosphate. The 1 and the 5 in this name refer to the locations of the bi (two) phosphates on the structure of the Ribulose.

Anyway, the resulting Carbon molecule is a 6 Carbon sugar, which is unstable so it forms two 3 Carbon compounds along with the help of a molecule of water, 3-Phosphoglyceric acid. One of these 3-Phosphoglyceric acids is used for other purposes within the plant, and the other one combines with another compound within the plant.

Now, it should be noted that the plant does not contain the structure for these reactions within one place, i.e. the chloroplast. The chemical procedures detailing the conversion of Carbon Dioxide and Water into 6-Carbon Sugar and Oxygen occur within the chloroplast and the mitochondria, however, both of these are located within the cell of a plant's leaf. Therefore, to trace the carbon as it travels through this pathway, one should note that there are two major processes occurring, which have been detailed in laborious fashion.

The first process is the conversion of 3 molecules of Carbon Dioxide into a 3 Carbon Sugar called G3P, or Glyceraldehyde 3-phosphate.

This process takes place within the chloroplast, and aids the use of sunlight to foster endothermic reactions. This is known as the Calvin cycle.

The next process creates the 6 Carbon sugar Glucose. It should be known that the Glucose created by this cycle is then used in several instances within the plant for creating its cell walls, proteins, DNA, starches, sugars, and for the storage and release of energy.

Now, to trace the Carbon throughout the entire leaf would involve knowing the outputs and mechanisms for each of these products, which would be do-able for certain levels of study. However, I believe the tracing of the carbon throughout the leaf can be done by examining the inputs and outputs of the various metabolic systems contained within its structures.

If you would like to research and describe these systems, they can be viewed at

https://en.wikipedia.org/wiki/Photosynthesis

Please let me know if this helps. Thank you!