The Carbon cycle

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The carbon cycle controls life on the planet earth. Which has been occurring since the beginning of time. Bacteria (and other microorganisms) control the world, they help regulate the environment by controlling the cycling of carbon. Plants, microorganisms such as prokaryotes, cyanobacteria, and methanogens are a major factor in the amount of carbon dioxide fixation in the atmosphere (TODAR). The carbon dioxide in the air is turned into organic material which can be used for growth in the organism that can use it (TODAR). Some of the reactions that take place are photosynthesis: CO2 + H2O -> CH2O + O2 (which takes carbon dioxide out of the atmosphere and pumps out oxygen) and respiration CH2O + O2 -> CO2 + H2O (which uses the oxygen created by the photosynthesis to create carbon dioxide)[BC1] (TODAR). Animals exhale CO2 while plants take in CO2 through photosynthesis. During the carbon cycle the oceans are constantly exchanging CO2 with the atmosphere (the ocean acts as a large carbon sink-holding the CO2 in place) to create a balance in the environment (U.S. Department of Commerce). The carbon cycle is important because carbon is the basis for life on the earth (U.S. Department of Commerce). Atmospheric CO2 protects the earth by trapping radiation which could jump off the planet (U.S. Department of Commerce). As more atmospheric carbon is availible more heat will be trapped, causing a warming effect which on the environment (U.S. Department of Commerce). Additional CO2 would cause a strain on the carbon cycle, which would require more natural methods to degrade the additional CO2 to counteract this warming effect (U.S. Department of Commerce). This is particularly devastating as the planet warms up more it can have disastrous effects on weather systems throughout the world.

Diagram of carbon cycle sources and sinks.

Outlines the natural carbon cycle, where atmospheric CO2 is in constant balance with ocean intake opf CO2. And the rate os respiration by the planet should be inline with rate of photosynthesis. But this is being push out of balance due to increase in industrial processes which are pushing out more CO2 than the planet can process.Taken from the U.S. Department of Commerce, National Oceanic & Atmospheric Administration (U.S. Department of Commerce).

Another important agent to humanity is chlorine. It has been used in the past as a weapon of war, but today it is used more commonly to kill off microorganisms present in water. It is particularly useful because it is effective at killing microorganisms while not toxic to higher life forms. This is particularly important because chlorination of drinking water prevents pathogenic microorganisms from being able to infect people and making them sick. The reason chlorine does this is because it is an effective bactericidal agent. This is because HOCL (hypochlorous acid) is key to killing microorganisms (CDC). According to the CDC, while the specific method has not been determined how chlorine purifies water can be by: decreaseing microorganism uptake of nutrients, ring chlorination of amino acids, disrupting DNA synthesis, , oxidation of critical compenents for cell, and many more [BC2](CDC). As a result of its versatility in killing microorgansisms chlorine is used in a variety of locations such as healthcare facilities as a disinfectant, as treatment in municipal water supplies, decontaminating blood spills, and many more (CDC). As a result the ability for chlorine to be able eliminate microorgranisms had made it crucial to the modern day world.

For the determination of chlorine demand (amount of chlorine that is bactericidal in nature), for this experiment to determine how if chlorine was successful in preventing Escherichia coli (E. coli). three test tubes had a solution of distilled water, lactose broth, and E. coli broth were tested against the effectivneness of chlorine being able to grow. If E. coli had metabolized the lactose then the solution would have turned yellow and had indication of gas produced. The purpose of this experiment was determine the chlorine demand of organic matter.

To determine if the oxidation of carbon dioxide had occurred two soil samples were tested, where one had an addition of glucose in it. NaOH was placed on the soil in a container and used as a carbon sink. If there was CO2 gas produced by the microorganisms in the soil the NaOH would have reacted with it to become Na2CO3. As long as the amount of HCl reacting did not equal the amount of NaOH initially incubated in the soil then carbon fixation had occurred. To determine the amount of Na2CO3 produced a titration was performed using HCl, it was done arithmetically as shown in the Appendix. The purpose of this experiment was to determine the how much CO2 was converted into carbohydrates via the microorganisms in the soil and whether the use of glucose as an energy source for soil microorganisms was possible.

Methods and Materials

Please refer to Department of Biology, 2015, Biology 241 Introduction to the microbial world lab manual, Experiment 9: Determination of Chlorine demand, pp. 62-65 and Experiment 10: Oxidation of a Carbon source by microorganisms. All methods and materials were followed without any deviation.


Table 1, Results from lactose broth tubes: if there was E. coli growth

SampleAcid producedGas formedGrowth of E. coli

  1. 0..01% peptone + chlorineyesyesyes
  1. Distilled water + chlorinenonono
  1. Distilled water no chlorineyesyesyes

Table 1 summarizes findings of experiment with respect to the growth of E. coli being present in the lactose broth tubes, with or without chlorine present. Where E. coli is confirmed if acid is produced (tube turns yellow) and gas is formed (can see gas bubble).

Table 2, Results from lactose broth tubes: Chlorine demand of organic matter

Residual chlorine in sampleChlorine present

Tube B (Demand free)3.0

Tube A (Demand)1.0

Chlorine demand of organic matter2.0

Table 2 summarizes findings of experiment with respect to the chlorine demand of organic matter in the lactose broth tube A which had 0.01% peptone solution included to encourage the growth of E. coli–see appendix for sample calculation-

Table 3, Results from oxidation of carbon: amount of CO2 evolved

SampleAmount of CO2 evolved

Unamended soil (control)12.32 mg CO2 / 50 g of soil

Amended soil (glucose)37.4 mg CO2 / 50 g of soil

Table 3 summarizes findings of experiment with respect to the amount of CO2 evolved in the soil sample after incubating for a week. NaOH was used as a carbon sink. A titration was performed to determine the amount of CO2 evolved-see appendix for sample calculations-


As stated before the carbon cycle is integral to the wellbeing of the planet. Carbon can exist in soil, fossil fuels, plants, atmosphere, ocean, and rocks each of which are considered reservoirs of carbon (NASA). Most of the earth’s carbon is stored in rocks (NASA). Carbon flows in-between each of these reservoirs constantly, and this is called the carbon cycle (NASA). Over the long term the carbon cycle is integral to preventing all the carbon on earth from entering the atmosphere (NASA). As it has been shown the higher level of CO2 lead to higher global temperatures (NASA). As a result of that, this cycle keeps the earths temperature relatively stable (NASA). The long run carbon cycle involves carbon from rocks, where acid rain combines with atmospheric carbon and as it hits the ground ions would bind the carbon to the surface (NASA). That carbon stored in rocks can eventually go back into the atmosphere from sources such as volcanos venting carbon or from tectonic movements (NASA). However this process takes 100-200 million years to complete (NASA). For the purposes of this report will not need to be nesscessary to be touched upon.

The fast carbon cycle takes roughly a year to complete (NASA).

For the soil samples the one with glucose in the sample was testing whether glucose could be used as an energy source for CO2 fixation. - NASA - CDC TOdar- carbon cycling - U.S. Department of Commerce, National Oceanic & Atmospheric Administration

[BC1]Look into sourcing

[BC2]I dunno the list might get hit